Showing 1–50 of 255 results for author: Lin, Z

A robust morphological classification method for galaxies using dual-encoding contrastive learning and multi-clustering voting on JWST/NIRCam images

Authors: Xiaolei Yin, Guanwen Fang, Shiying Lu, Zesen Lin, Yao Dai, Chichun Zhou

Abstract: The two-step galaxy morphology classification framework {\tt USmorph} successfully combines unsupervised machine learning (UML) with supervised machine learning (SML) methods. To enhance the UML step, we employed a dual-encoder architecture (ConvNeXt and ViT) to effectively encode images, contrastive learning to accurately extract features, and principal component analysis to efficiently reduce di… ▽ More The two-step galaxy morphology classification framework {\tt USmorph} successfully combines unsupervised machine learning (UML) with supervised machine learning (SML) methods. To enhance the UML step, we employed a dual-encoder architecture (ConvNeXt and ViT) to effectively encode images, contrastive learning to accurately extract features, and principal component analysis to efficiently reduce dimensionality. Based on this improved framework, a sample of 46,176 galaxies at $0<z<4.2$, selected in the COSMOS-Web field, is classified into five types using the JWST near-infrared images: 33\% spherical (SPH), 25\% early-type disk (ETD), 25\% late-type disk (LTD), 7\% irregular (IRR), and 10\% unclassified (UNC) galaxies. We also performed parametric (S{é}rsic index, $n$,and effective radius, $r_{\rm e}$) and nonparametric measurements (Gini coefficient, $G$, the second-order moment of light, $M_{\rm 20}$, concentration, $C$, multiplicity, $Ψ$, and three other parameters from the MID statistics) for massive galaxies ($M_*>10^9 M_\odot$) to verify the validity of our galaxy morphological classification system. The analysis of morphological parameters is consistent with our classification system: SPH and ETD galaxies with higher $n$, $G$, and $C$ tend to be more bulge-dominated and more compact compared with other types of galaxies. This demonstrates the reliability of this classification system, which will be useful for a forthcoming large-sky survey from the Chinese Space Station Telescope. △ Less

Submitted 18 December, 2025; originally announced December 2025.

Comments: Published in A&A

Journal ref: A&A(2025),703,A13

An updated efficient galaxy morphology classification model based on ConvNeXt encoding with UMAP dimensionality reduction

Authors: Guanwen Fang, Shiwei Zhu, Jun Xu, Shiying Lu, Chichun Zhou, Yao Dai, Zesen Lin, Xu Kong

Abstract: We present an enhanced unsupervised machine learning (UML) module within our previous \texttt{USmorph} classification framework featuring two components: (1) hierarchical feature extraction via a pre-trained ConvNeXt convolutional neural network (CNN) with transfer learning, and (2) nonlinear manifold learning using Uniform Manifold Approximation and Projection (UMAP) for topology-aware dimensiona… ▽ More We present an enhanced unsupervised machine learning (UML) module within our previous \texttt{USmorph} classification framework featuring two components: (1) hierarchical feature extraction via a pre-trained ConvNeXt convolutional neural network (CNN) with transfer learning, and (2) nonlinear manifold learning using Uniform Manifold Approximation and Projection (UMAP) for topology-aware dimensionality reduction. This dual-stage design enables efficient knowledge transfer from large-scale visual datasets while preserving morphological pattern geometry through UMAP's neighborhood preservation. We apply the upgraded UML on I-band images of 99,806 COSMOS galaxies at redshift $0.2<z<1.2$ (to ensure rest-frame optical morphology) with $I_{\mathrm{mag}}<25$. The predefined cluster number is optimized to 20 (reduced from 50 in the original framework), achieving significant computational savings. The 20 algorithmically identified clusters are merged into five physical morphology types. About 51\% of galaxies (50,056) were successfully classified. To assess classification effectiveness, we tested morphological parameters for massive galaxies with $M_{*}>10^{9}~M_{\odot}$. Our classification results align well with galaxy evolution theory. This improved algorithm significantly enhances galaxy morphology classification efficiency, making it suitable for large-scale sky surveys such as those planned with the China Space Station Telescope (CSST). △ Less

Submitted 17 December, 2025; v1 submitted 17 December, 2025; originally announced December 2025.

Comments: Accepted for publication in AJ

Dual-coding contrastive learning based on ConvNeXt and ViT models for morphological classification of galaxies in COSMOS-Web

Authors: Shiwei Zhu, Guanwen Fang, Chichun Zhou, Jie Song, Zesen Lin, Yao Dai, Xu Kong

Abstract: In our previous works, we proposed a machine learning framework named \texttt{USmorph} for efficiently classifying galaxy morphology. In this study, we propose a self-supervised method called contrastive learning to upgrade the unsupervised machine learning (UML) part of the \texttt{USmorph} framework, aiming to improve the efficiency of feature extraction in this step. The upgraded UML method pri… ▽ More In our previous works, we proposed a machine learning framework named \texttt{USmorph} for efficiently classifying galaxy morphology. In this study, we propose a self-supervised method called contrastive learning to upgrade the unsupervised machine learning (UML) part of the \texttt{USmorph} framework, aiming to improve the efficiency of feature extraction in this step. The upgraded UML method primarily consists of the following three aspects. (1) We employ a Convolutional Autoencoder to denoise galaxy images and the Adaptive Polar Coordinate Transformation to enhance the model's rotational invariance. (2) A pre-trained dual-encoder convolutional neural network based on ConvNeXt and ViT is used to encode the image data, while contrastive learning is then applied to reduce the dimension of the features. (3) We adopt a Bagging-based clustering model to cluster galaxies with similar features into distinct groups. By carefully dividing the redshift bins, we apply this model to the rest-frame optical images of galaxies in the COSMOS-Web field within the redshift range of $0.5 < z < 6.0$. Compared to the previous algorithm, the improved UML method successfully classifies 73\% galaxies. Using the GoogleNet algorithm, we classify the morphology of the remaining 27\% galaxies. To validate the reliability of our updated algorithm, we compared our classification results with other galaxy morphological parameters and found a good consistency with galaxy evolution. Benefiting from its higher efficiency, this updated algorithm is well-suited for application in future China Space Station Telescope missions. △ Less

Submitted 17 December, 2025; v1 submitted 17 December, 2025; originally announced December 2025.

Comments: Published in APJS

Journal ref: ApJS (2025), 278 39

JWST TRAPPIST-1 e/b Program: Motivation and first observations

Authors: Natalie H. Allen, Néstor Espinoza, V. A. Boehm, Caleb I. Cañas, Kevin B. Stevenson, Nikole K. Lewis, Ryan J. MacDonald, Brett M. Morris, Eric Agol, Knicole Colón, Hannah Diamond-Lowe, Ana Glidden, Amélie Gressier, Jingcheng Huang, Zifan Lin, Douglas Long, Dana R. Louie, Meredith A. MacGregor, Laurent Pueyo, Benjamin V. Rackham, Sukrit Ranjan, Sara Seager, Guadalupe Tovar Mendoza, Jeff A. Valenti, Daniel Valentine , et al. (2 additional authors not shown)

Abstract: One of the forefront goals in the field of exoplanets is the detection of an atmosphere on a temperate terrestrial exoplanet, and among the best suited systems to do so is TRAPPIST-1. However, JWST transit observations of the TRAPPIST-1 planets show significant contamination from stellar surface features that we are unable to confidently model. Here, we present the motivation and first observation… ▽ More One of the forefront goals in the field of exoplanets is the detection of an atmosphere on a temperate terrestrial exoplanet, and among the best suited systems to do so is TRAPPIST-1. However, JWST transit observations of the TRAPPIST-1 planets show significant contamination from stellar surface features that we are unable to confidently model. Here, we present the motivation and first observations of our JWST multi-cycle program of TRAPPIST-1 e, which utilize close transits of the airless TRAPPIST-1 b to model-independently correct for stellar contamination, with the goal of determining whether TRAPPIST-1 e has an Earth-like mean molecular weight atmosphere containing CO$_2$. We present our simulations, which show that with the 15 close transit observations, we will be able to detect this atmosphere on TRAPPIST-1 e at $Δ\ln\,Z=5$ or greater confidence assuming we are able to correct for stellar contamination using the close transit observations. We also show the first three observations of our program. We find that our ability to correct for stellar contamination can be inhibited when strong stellar flares are present, as flares can break the assumption that the star does not change meaningfully between planetary transits. The cleanest observation demonstrates the removal of stellar contamination contribution through an increased preference for a flat line over the original TRAPPIST-1 e spectrum, but highlights how minor data analysis assumptions can propagate significantly when searching for small atmospheric signals. This is amplified when using the signals from multiple planets, which is important to consider as we continue our atmospheric search. △ Less

Submitted 8 December, 2025; originally announced December 2025.

Comments: 26 pages, 15 figures, accepted for publication in AJ

Multi-band ALMA Polarization Observations of BHB07-11 Reveal Aligned Dust Grains in Complex Spiral Arm Structures

Authors: Austen Fourkas, Leslie W. Looney, Zhe-Yu Daniel Lin, Martin Radecki, Zhi-Yun Li, John J. Tobin, Ian W. Stephens, Manuel Fernández-López, Haifeng Yang, Woojin Kwon, Rachel Harrison

Abstract: Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB07-11, a Class I protobinary object in the Pipe Nebula with… ▽ More Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB07-11, a Class I protobinary object in the Pipe Nebula with complex spiral arm structures in its circumbinary disk. While magnetic fields are often invoked to explain grain alignment in the interstellar medium, the contrasting conditions in circumstellar disk environments demand further investigation into grain alignment mechanisms. To determine BHB07-11's dominant polarization mechanism, we leverage ALMA polarization-mode dust continuum observations in Bands 3 ($λ$=3.1 mm), 6 ($λ$=1.3 mm), and 7 ($λ$=0.87 mm), in combination with high-resolution dust continuum and spectral line observations in Band 6. Observed polarization vectors in each band are consistent with emission from aligned grains and follow the structure of the spiral arms as shown in the high-resolution observations. Given the relationship between the observed polarization vector orientation and the spiral arms, we find that the polarization morphology is most consistent with grains aligned through a relative velocity flow between gas and dust in the spiral arms, as envisioned in the recently developed badminton birdie-like alignment mechanism, rather than alignment with a magnetic field or other known alignment mechanisms. △ Less

Submitted 5 December, 2025; originally announced December 2025.

Comments: Accepted to ApJ, 30 pages, 21 figures

The Faintest, Extremely Variable X-ray Tidal Disruption Event from a Supermassive Black Hole Binary?

Authors: Mengqiu Huang, Yongquan Xue, Shuo Li, Fukun Liu, Shifu Zhu, Jin-Hong Chen, Rong-Feng Shen, Yibo Wang, Yi Yang, Ning Jiang, Franz Erik Bauer, Cristian Vignali, Fan Zou, Jialai Wang, Alexei V. Filippenko, Bin Luo, Chen Qin, Jonathan Quirola-Vásquez, Jun-Xian Wang, Lulu Fan, Mouyuan Sun, Qingwen Wu, Qingling Ni, Thomas G. Brink, Tinggui Wang , et al. (8 additional authors not shown)

Abstract: Tidal disruption events (TDEs), which occur when stars enter the tidal radii of supermassive black holes (SMBHs) and are subsequently torn apart by their tidal forces, represent intriguing phenomena that stimulate growing research interest and pose an increasing number of puzzles in the era of time-domain astronomy. Here we report an unusual X-ray transient, XID 935, discovered in the 7 Ms Chandra… ▽ More Tidal disruption events (TDEs), which occur when stars enter the tidal radii of supermassive black holes (SMBHs) and are subsequently torn apart by their tidal forces, represent intriguing phenomena that stimulate growing research interest and pose an increasing number of puzzles in the era of time-domain astronomy. Here we report an unusual X-ray transient, XID 935, discovered in the 7 Ms Chandra Deep Field-South, the deepest X-ray survey ever. XID 935 experienced an overall X-ray dimming by a factor of more than 40 between 1999 and 2016. Not monotonically decreasing during this period, its X-ray luminosity increased by a factor $> 27$ within 2 months, from $L_{\rm 0.5-7\ keV}<10^{40.87}$ erg s$^{-1}$ (10 October 2014 -- 4 January 2015) to $L_{\rm 0.5-7\ keV}=10^{42.31\pm 0.20}$ erg s$^{-1}$ (16 March 2015). The X-ray position of XID 935 is located at the center of its host galaxy with a spectroscopic redshift of 0.251, whose optical spectra do not display emission characteristics associated with an active galactic nucleus. The peak 0.5--2.0 keV flux is the faintest among all the X-ray-selected TDE candidates to date. Thanks to a total exposure of $\sim 9.5$ Ms in the X-ray bands, we manage to secure relatively well-sampled, 20-year-long X-ray light curves of this deepest X-ray-selected TDE candidate. We find that a partial TDE model could not explain the main declining trend. An SMBH binary TDE model is in acceptable accordance with the light curves of XID 935; however, it fails to match short-timescale fluctuations exactly. Therefore, the exceptional observational features of XID 935 provide a key benchmark for refining quantitative TDE models and simulations. △ Less

Submitted 26 November, 2025; originally announced November 2025.

Comments: 31 pages, 6 figures, 1 table, accepted by The Innovation

Journal ref: The Innovation 7(3), 101169 (2026)

Detection of disk-jet co-precession in a tidal disruption event

Authors: Yanan Wang, Zikun Lin, Linhui Wu, Weihua Lei, Shuyuan Wei, Shuang-Nan Zhang, Long Ji, Santiago del Palacio, Ranieri D. Baldi, Yang Huang, Jifeng Liu, Bing Zhang, Aiyuan Yang, Rurong Chen, Yangwei Zhang, Ailing Wang, Lei Yang, Panos Charalampopoulos, David R. A. Williams-Baldwin, Zhu-Heng Yao, Fu-Guo Xie, Defu Bu, Hua Feng, Xinwu Cao, Hongzhou Wu , et al. (24 additional authors not shown)

Abstract: Theories and simulations predict that intense spacetime curvature near black holes bends the trajectories of light and matter, driving disk and jet precession under relativistic torques. However, direct observational evidence of disk-jet co-precession remains elusive. Here, we report the most compelling case to date: a tidal disruption event (TDE) exhibiting unprecedented 19.6-day quasi-periodic v… ▽ More Theories and simulations predict that intense spacetime curvature near black holes bends the trajectories of light and matter, driving disk and jet precession under relativistic torques. However, direct observational evidence of disk-jet co-precession remains elusive. Here, we report the most compelling case to date: a tidal disruption event (TDE) exhibiting unprecedented 19.6-day quasi-periodic variations in both X-rays and radio, with X-ray amplitudes exceeding an order of magnitude. The nearly synchronized X-ray and radio variations suggest a shared mechanism regulating the emission regions. We demonstrate that a disk-jet Lense-Thirring precession model successfully reproduces these variations while requiring a low-spin black hole. This study uncovers previously uncharted short-term radio variability in TDEs, highlights the transformative potential of high-cadence radio monitoring, and offers profound insights into disk-jet physics. △ Less

Submitted 16 November, 2025; originally announced November 2025.

Comments: 76 pages, 13 figures (initial submission; in press at Science Advances)

glitterin: Towards Replacing the Role of Lorenz-Mie Theory in Astronomy Using Neural Networks Trained on Light Scattering of Irregularly Shaped Grains

Authors: Zhe-Yu Daniel Lin, Alycia J. Weinberger, Evgenij Zubko, Jessica A. Arnold, Gorden Videen

Abstract: Light scattering by dust particles is often modeled assuming the dust is spherical for numerical simplicity and speed. However, real dust particles have highly irregular morphologies that significantly affect their scattering properties. We have developed glitterin, a neural network trained to predict light scattering from irregularly shaped dust grains, offering a computationally efficient altern… ▽ More Light scattering by dust particles is often modeled assuming the dust is spherical for numerical simplicity and speed. However, real dust particles have highly irregular morphologies that significantly affect their scattering properties. We have developed glitterin, a neural network trained to predict light scattering from irregularly shaped dust grains, offering a computationally efficient alternative to Lorenz-Mie theory. We computed scattering properties using the Discrete Dipole Approximation code ADDA for irregularly shaped particles across size parameters x from 0.1 to 65, covering a range in complex refractive index m that includes astrosilicates, pyroxene, enstatite, water-ice, etc. The neural network operates at millisecond timescales while maintaining superior accuracy compared to linear interpolation. Irregular grains exhibit x-dependent deviations from spherical predictions. At small x, cross-sections approach volume-equivalent spheres for low m. At large x, irregular grains show enhanced cross-sections due to greater geometric extension. Increasing m also enhances the absorption cross-section relative to the volume-equivalent spheres. This differential x and m dependence creates mid-IR solid-state features distinct from predictions from spherical grains. Validation against laboratory measurements of forsterite and hematite demonstrates that our neural network captures both qualitative and quantitative behaviors more accurately than spherical models. Millimeter-wavelength applications reveal that spherical grains produce opposite polarization signatures compared to irregular grains, potentially relaxing stringent ~100um grain size constraints in protoplanetary disks. glitterin is publicly available and alleviates the computational barriers to incorporating emission and scattering of realistic grain morphologies. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 24 pages, 12 figures, accepted for publication in PASP. Training data, trained neural networks, and the python interface are publicly available. Abstract abridged for arXiv requirements

Mock Observations for the CSST Mission: HSTDM--Synthetic Data Generation

Authors: SiYuan Tan, WenYin Duan, YiLong Zhang, YiPing Ao, Yan Gong, ZhenHui Lin, Xuan Zhang, Yong Shi, Jing Tang, Jing Li, RuiQing Mao, Sheng-Cai Shi

Abstract: The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the China Space Station Telescope (CSST), will offer great opportunities for the discovery of Terahertz Astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergoes meticulous calibration and pro… ▽ More The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the China Space Station Telescope (CSST), will offer great opportunities for the discovery of Terahertz Astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergoes meticulous calibration and processing through the HSTDM data processing pipeline (HSTDM pipeline for short) to ensure the accuracy and effectiveness of the final science data to be archived for further research. This process necessitates that the HSTDM pipeline address instrumental artifacts and effects as well as the coordination of data flow of the scheduled observing sequences under all observing modes of HSTDM within the CSST automated processing environment. As the understanding of CSST HSTDM data processing develops during the pipeline development stage, it becomes essential to assess the accuracy, the robustness and the performance of the HSTDM pipeline under all observing modes of HSTDM so that components of the HSTDM pipeline be rationally added, removed, amended or extended within the modular framework. In this paper, we develop practical simulation methods to facilitate this need. The contribution of synthetic data generation of HSTDM observation includes two parts: 1. HSTDM instrumental effect simulation based on both real testing profiles and simulated models; 2. Observing data flow generation based on HSTDM observing mode scenario. The simulation methods have been implemented and shown to be practical in testing the HSTDM pipeline during the development stage. △ Less

Submitted 13 November, 2025; v1 submitted 12 November, 2025; originally announced November 2025.

Comments: 22 pages, 13 figures

Revealing the Temporally Stable Bimodal Energy Distribution of FRB 20121102A with a Tripled Burst Set from AI Detections

Authors: Yidan Wang, Jing Han, Pei Wang, Di Li, Hanting Chen, Yuchuan Tian, Erbil Gugercinoglu, Jianing Tang, Zihan Zhang, Kaichao Wu, Xiaoli Zhang, Yuhao Zhu, Jinhuang Cao, Mingtai Chen, Jiapei Feng, Zhaoyu Huai, Zitao Lin, Jieming Luan, Hongbin Wang, Junjie Zhao, Chaowei Tsai, Weiwei Zhu, Yongkun Zhang, Yi Feng, Aiyuan Yang , et al. (12 additional authors not shown)

Abstract: Active repeating Fast Radio Bursts (FRBs), with their large number of bursts, burst energy distribution, and their potential energy evolution, offer critical insights into the FRBs emission mechanisms. Traditional pipelines search for bursts through conducting dedispersion trials and looking for signals above certain fluence thresholds, both of which could result in missing weak and narrow-band bu… ▽ More Active repeating Fast Radio Bursts (FRBs), with their large number of bursts, burst energy distribution, and their potential energy evolution, offer critical insights into the FRBs emission mechanisms. Traditional pipelines search for bursts through conducting dedispersion trials and looking for signals above certain fluence thresholds, both of which could result in missing weak and narrow-band bursts. In order to improve the completeness of the burst set, we develop an End-to-end DedispersE-agnostic Nonparametric AI model (EDEN), which directly detect bursts from dynamic spectrum and is the first detection pipeline that operates without attempting dedispersion. We apply EDEN to archival FAST L-band observations during the extreme active phase of the repeating source FRB 20121102A, resulting in the largest burst set for any FRB to date, which contains 5,927 individual bursts, tripling the original burst set. The much enhanced completeness enables a refined analysis of the temporal behavior of energy distribution, revealing that the bimodal energy distribution remains stable over time. It is rather an intrinsic feature of the emission mechanisms than a consequence of co-evolving with burst rate. △ Less

Submitted 8 October, 2025; originally announced October 2025.

JWST occultation reveals unforeseen complexity in Chariklo's ring system

Authors: Pablo Santos-Sanz, Altair R. Gomes-Júnior, Bruno E. Morgado, Yucel Kilic, Csilla E. Kalup, Csaba Kiss, Chrystian L. Pereira, Bryan J. Holler, Nicolás Morales, José Luis Ortiz, Bruno Sicardy, Juan Luis Rizos, John Stansberry, Richard G. French, Heidi B. Hammel, Zhong-Yi Lin, Damya Souami, Josselin Desmars, Stefanie N. Milam, Felipe Braga-Ribas, Marcelo Assafin, Gustavo Benedetti-Rossi, Julio I. B. Camargo, René Duffard, Flavia L. Rommel , et al. (3 additional authors not shown)

Abstract: Ring systems have been discovered around several small bodies in the outer Solar System through stellar occultations. While such measurements provide key information about ring geometry and dynamical interactions, little is known about their origins, lifetimes, evolutionary pathways, or compositions. Here we report near-infrared observations with the James Webb Space Telescope (JWST) of a stellar… ▽ More Ring systems have been discovered around several small bodies in the outer Solar System through stellar occultations. While such measurements provide key information about ring geometry and dynamical interactions, little is known about their origins, lifetimes, evolutionary pathways, or compositions. Here we report near-infrared observations with the James Webb Space Telescope (JWST) of a stellar occultation by (10199) Chariklo, a Centaur known to host a double-ring system. Our JWST measurements show that Chariklo's inner dense ring has become significantly more opaque than in previous observations, pointing to ongoing replenishment processes or dynamical restructuring. In contrast, the outer ring exhibits a much weaker near-infrared occultation signature than seen in earlier visible-light detections. This discrepancy may reflect material loss, suggesting that the outer ring could be transient, or may arise from wavelength-dependent opacity. These scenarios, which are not mutually exclusive, point to an unprecedented level of complexity in small-body ring systems, distinct from those observed around any other minor bodies in the Solar System. △ Less

Submitted 17 December, 2025; v1 submitted 7 October, 2025; originally announced October 2025.

Comments: This manuscript contains 32 pages, 10 figures, and 4 tables

JWST-TST DREAMS: The Nightside Emission and Chemistry of WASP-17b

Authors: Jacob Lustig-Yaeger, Kristin S. Sotzen, Kevin B. Stevenson, Shang-Min Tsai, Ryan C. Challener, Jayesh Goyal, Nikole K. Lewis, Dana R. Louie, L. C. Mayorga, Daniel Valentine, Hannah R. Wakeford, Lili Alderson, Natalie H. Allen, Thomas J. Fauchez, Ana Glidden, Amélie Gressier, Sarah M. Hörst, Jingcheng Huang, Zifan Lin, Avi M. Mandell, Elijah Mullens, Sarah Peacock, Edward W. Schwieterman, Jeff A. Valenti, C. Matt Mountain , et al. (2 additional authors not shown)

Abstract: Theoretical studies have suggested using planetary infrared excess (PIE) to detect and characterize the thermal emission of transiting and non-transiting exoplanets, however the PIE technique requires empirical validation. Here we apply the PIE technique to a combination of JWST NIRSpec G395H transit and eclipse measurements of WASP-17b, a hot Jupiter orbiting an F-type star, obtained consecutivel… ▽ More Theoretical studies have suggested using planetary infrared excess (PIE) to detect and characterize the thermal emission of transiting and non-transiting exoplanets, however the PIE technique requires empirical validation. Here we apply the PIE technique to a combination of JWST NIRSpec G395H transit and eclipse measurements of WASP-17b, a hot Jupiter orbiting an F-type star, obtained consecutively (0.5 phase or 1.8 days apart) as part of the JWST-TST program to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). Using the in-eclipse measured stellar spectrum to circumvent the need for ultra-precise stellar models, we extract the first JWST nightside emission spectrum of WASP-17b using only transit and eclipse data thereby performing a controlled test of the PIE technique. From the WASP-17b nightside spectrum, we measure a nightside equilibrium temperature of $1005 \pm 256$ K and find tentative evidence for nightside SO2 absorption ($\ln B = 1.45$, $2.3σ$). In context with the dayside, the temperature of the nightside is consistent with (1) previous eclipse mapping findings that suggest relatively inefficient day-night heat transport, and (2) a non-zero bond albedo of $0.42^{+0.06}_{-0.10}$. SO2 on the nightside, if confirmed, would represent the first direct evidence for transport-induced chemistry, matching previous model predictions, and opening a new door into the 3D nature of giant exoplanets. Our results suggest that PIE is feasible with JWST/NIRSpec for two epochs separated in time by significantly less than the rotation period of the host star. △ Less

Submitted 7 October, 2025; originally announced October 2025.

Comments: 21 pages, 9 figures, 2 tables, revised in response to ApJL reviewer comments

SDSS-IV MaNGA: Data-Model Discrepancy in Temperature-sensitive Line Ratios for Star-forming Galaxies

Authors: Ziming Peng, Renbin Yan, Xihan Ji, Zesen Lin, Man-Yin Leo Lee

Abstract: Gas-phase metallicity is a fundamental parameter that helps constrain the star-forming history and chemical evolution of a galaxy. Measuring electron temperature through auroral-to-strong line ratios is a direct approach to deriving metallicity. However, there is a longstanding discrepancy between metallicity measured through the direct method and that based on the photoionization models. This pap… ▽ More Gas-phase metallicity is a fundamental parameter that helps constrain the star-forming history and chemical evolution of a galaxy. Measuring electron temperature through auroral-to-strong line ratios is a direct approach to deriving metallicity. However, there is a longstanding discrepancy between metallicity measured through the direct method and that based on the photoionization models. This paper aims to verify and understand the discrepancies. We bin ~ 1.5 million spaxels from SDSS-IV MaNGA according to metallicity and ionization parameters derived from theoretical strong-line calibrations. We stack the spectra of spaxels within each bin and measure the flux of strong lines and faint auroral lines. Auroral lines for [OII], [SII], [OIII], and [SIII] are detected in the stacked spectra of most bins, and the [NII] auroral line is detected in fewer bins. We apply an empirical method to correct dust attenuation, which makes more realistic corrections for low ionization lines. We derive electron temperatures for these five ionic species and measure the oxygen and sulfur abundances using the direct method. We present the resulting abundance measurements and compare them with those model-calibrated strong-line abundances. The chemical abundances measured with the direct method are lower than those derived from the photoionization model, with a median of 0.09 dex. This discrepancy is smaller compared to the results based on other metallicity calibrations previously reported. However, we notice that the direct method could not account for the variation in ionization parameters, indicating that the precise calibration of metallicity using the direct method has yet to be fully realized. We report significant discrepancies between data and the photoionization model, which illustrates that the one-dimensional photoionization model is incapable of representing the complexity of real situations. △ Less

Submitted 23 September, 2025; originally announced September 2025.

Comments: 17 pages, 12 figures, accepted by A&A. Comments are welcome

Journal ref: A&A 703, A236 (2025)

JWST-TST DREAMS: Sulfur dioxide in the atmosphere of the Neptune-mass planet HAT-P-26 b from NIRSpec G395H transmission spectroscopy

Authors: Amélie Gressier, Natasha E. Batalha, Nicholas Wogan, Lili Alderson, Dominic Doud, Néstor Espinoza, Ryan J. MacDonald, Hannah R. Wakeford, Jeff A. Valenti, Nikole K. Lewis, Sara Seager, Kevin B. Stevenson, Natalie H. Allen, Caleb I. Cañas, Ryan C. Challener, Ana Glidden, Jingcheng Huang, Zifan Lin, Dana R. Louie, Cathal Maguire, Elijah Mullens, Kristin Sotzen, Daniel Valentine, Mark Clampin, Laurent Pueyo , et al. (2 additional authors not shown)

Abstract: We present the James Webb Space Telescope (JWST) transmission spectrum of the exoplanet HAT-P-26 b (18.6 Earth masses, 6.33 Earth radii), based on a single transit observed with the JWST NIRSpec G395H grating. We detect water vapor (ln B = 4.1), carbon dioxide (ln B = 85.6), and sulfur dioxide (ln B = 13.5) with high confidence, along with marginal indications for hydrogen sulfide and carbon monox… ▽ More We present the James Webb Space Telescope (JWST) transmission spectrum of the exoplanet HAT-P-26 b (18.6 Earth masses, 6.33 Earth radii), based on a single transit observed with the JWST NIRSpec G395H grating. We detect water vapor (ln B = 4.1), carbon dioxide (ln B = 85.6), and sulfur dioxide (ln B = 13.5) with high confidence, along with marginal indications for hydrogen sulfide and carbon monoxide (ln B < 0.5). The detection of SO2 in a warm super-Neptune sized exoplanet (radius about 6 Earth radii) bridges the gap between previous detections in hot Jupiters and sub-Neptunes, highlighting the role of disequilibrium photochemistry across a broad range of exoplanet atmospheres, including those cooler than 1000 K. Our precise measurements of carbon, oxygen, and sulfur indicate an atmospheric metallicity of about 10 times solar and a sub-solar C/O ratio. Retrieved molecular abundances are consistent within 2 sigma with predictions from self-consistent models including photochemistry. The elevated CO2 abundance and possible H2S signal may also reflect sensitivities to the thermal structure, cloud properties, or additional disequilibrium processes such as vertical mixing. We compare the SO2 abundance in HAT-P-26 b with that of ten other JWST-observed giant exoplanets, and find a correlation with atmospheric metallicity. The trend is consistent with the prediction from Crossfield (2023), showing a steep rise in SO2 abundance at low metallicities, and a more gradual increase beyond 30 times solar. This work is part of a series of studies by our JWST Telescope Scientist Team (JWST-TST), in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). △ Less

Submitted 19 September, 2025; originally announced September 2025.

Comments: Accepted for Publication in the Astronomical Journal, September 16, 2025

Scientific Objectives of the Xue-shan-mu-chang 15-meter Submillimeter Telescope

Authors: XSMT Project Collaboration Group, Yiping Ao, Jin Chang, Zhiwei Chen, Xiangqun Cui, Kaiyi Du, Fujun Du, Yan Gong, Zhanwen Han, Gregory Herczeg, Luis C. Ho, Jie Hu, Yipeng Jing, Sihan Jiao, Binggang Ju, Jing Li, Xiaohu Li, Xiangdong Li, Lingrui Lin, Zhenhui Lin, Daizhong Liu, Dong Liu, Guoxi Liu, Zheng Lou, Dengrong Lu , et al. (26 additional authors not shown)

Abstract: Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China,… ▽ More Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China, marks a major milestone for Chinese astronomy, establishing the China mainland's first independently developed, world-class submillimeter facility. Equipped with state-of-the-art instruments, XSMT-15m will address a diverse range of frontier scientific questions spanning extragalactic astronomy, Galactic structure, time-domain astrophysics, and astrochemistry. In synergy with current and forthcoming observatories, XSMT-15m will illuminate the formation and evolution of galaxies, unravel the physical and chemical processes shaping the interstellar medium, and explore transient phenomena in the submillimeter regime. These capabilities will advance our understanding across extragalactic astronomy, Galactic ecology, astrochemistry, and time-domain astrophysics, inaugurating a new era for submillimeter research in China and the northern hemisphere. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: Accepted by Science China Physics, Mechanics & Astronomy

JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

Authors: Néstor Espinoza, Natalie H. Allen, Ana Glidden, Nikole K. Lewis, Sara Seager, Caleb I. Cañas, David Grant, Amélie Gressier, Shelby Courreges, Kevin B. Stevenson, Sukrit Ranjan, Knicole Colón, Brett M. Morris, Ryan J. MacDonald, Douglas Long, Hannah R. Wakeford, Jeff A. Valenti, Lili Alderson, Natasha E. Batalha, Ryan C. Challener, Jingcheng Huang, Zifan Lin, Dana R. Louie, Elijah Mullens, Daniel Valentine , et al. (10 additional authors not shown)

Abstract: TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and that resides in the habitable zone of its star -- located at a distance from its star such that it might, with the right atmosphere, sustain liquid water on its surface. Here, we present a set of 4 JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e obtained from mid to late 2023. Our… ▽ More TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and that resides in the habitable zone of its star -- located at a distance from its star such that it might, with the right atmosphere, sustain liquid water on its surface. Here, we present a set of 4 JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e obtained from mid to late 2023. Our transmission spectra exhibit similar levels of stellar contamination as observed in prior works for other planets in the TRAPPIST-1 system (Lim et al, 2023; Radica et al., 2024), but over a wider wavelength range, showcasing the challenge of characterizing the TRAPPIST-1 planets even at relatively long wavelengths (3-5 um). While we show that current stellar modeling frameworks are unable to explain the stellar contamination features in our spectra, we demonstrate that we can marginalize over those features instead using Gaussian Processes, which enables us to perform novel exoplanet atmospheric inferences with our transmission spectra. In particular, we are able to rule out cloudy, primary H$_2$-dominated ($\gtrsim$ 80$\%$ by volume) atmospheres at better than a 3$σ$ level. Constraints on possible secondary atmospheres on TRAPPIST-1 e are presented in a companion paper (Glidden et al., 2025). Our work showcases how JWST is breaking ground into the precisions needed to constrain the atmospheric composition of habitable-zone rocky exoplanets. △ Less

Submitted 5 September, 2025; originally announced September 2025.

Comments: Published in ApJ Letters, 16 pages, 4 figures (not including appendix). Check the companion paper (Glidden+2025) for secondary atmospheric interpretation. Data and scripts to reproduce all figures: https://zenodo.org/records/16125662

JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e

Authors: Ana Glidden, Sukrit Ranjan, Sara Seager, Néstor Espinoza, Ryan J. MacDonald, Natalie H. Allen, Caleb I. Cañas, David Grant, Amélie Gressier, Kevin B. Stevenson, Natasha E. Batalha, Nikole K. Lewis, Douglas Long, Hannah R. Wakeford, Lili Alderson, Ryan C. Challener, Knicole Colón, Jingcheng Huang, Zifan Lin, Dana R. Louie, Elijah Mullens, Kristin S. Sotzen, Jeff A. Valenti, Daniel Valentine, Mark Clampin , et al. (3 additional authors not shown)

Abstract: The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system. Within the TRAPPIST-1 system, planet e stands out as highly likely to sustain surface liquid water if it possesses an atmosphere. Recently, we reported the first JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e, revealing significant stellar contamination, wh… ▽ More The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system. Within the TRAPPIST-1 system, planet e stands out as highly likely to sustain surface liquid water if it possesses an atmosphere. Recently, we reported the first JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e, revealing significant stellar contamination, which varied between the four visits. Here, we assess the range of planetary atmospheres consistent with our transmission spectrum. We explore a wide range of atmospheric scenarios via a hierarchy of forward modeling and retrievals. We do not obtain strong evidence for or against an atmosphere. Our results weakly disfavor CO$_2$-rich atmospheres for pressures corresponding to the surface of Venus and Mars and the cloud tops of Venus at 2$σ$. We exclude H$_2$-rich atmospheres containing CO$_2$ and CH$_4$ in agreement with past work, but find that higher mean molecular weight, N$_2$-rich atmospheres with trace CO$_2$ and CH$_4$ are permitted by the data. Both a bare rock and N$_2$-rich atmospheric scenario provide adequate fits to the data, but do not fully explain all features, which may be due to either uncorrected stellar contamination or atmospheric signals. Ongoing JWST observations of TRAPPIST-1 e, exploiting consecutive transits with TRAPPIST-1 b, will offer stronger constraints via a more effective stellar contamination correction. The present work is part of the JWST Telescope Scientist Team (JWST-TST) Guaranteed Time Observations, which is performing a Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). △ Less

Submitted 5 September, 2025; originally announced September 2025.

Comments: 29 pages, 8 figures, accepted for publication in ApJL

IGR J17091-3624: Newly Formed Periodic Dips and Multiwavelength Activity During the 2025 Outburst

Authors: Zikun Lin, Yanan Wang, Shuyuan Wei, Yongkang Sun, Long Ji, Samaporn Tinyanont, Meng Sun, Song Wang, Diego Altamirano, Douglas J. K. Buisson, Wenxiong Li, Qian Chen, Jifeng Liu, Shuang-Nan Zhang, Wei Wang, Zhen Guo, Pathompong Butpan, Rungrit Anutarawiramkul

Abstract: The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spect… ▽ More The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spectral hardness. This is the first time such quasi-periodic dipping behavior has been observed in this target since discovery. Our spectral analysis shows that the dips can be explained by obscuration from an ionized absorber characterized by an ionization parameter of $logξ$ ~1-3 erg cm s$^{-1}$ and an equivalent hydrogen column density of $N^{\rm zxipcf}_{\rm H}$~(1-30)$\times10^{22}$ cm$^{-2}$. The periodic reappearance of the absorber is likely caused by obscuring material located in the outer accretion disk, modulated by the binary orbital period. If confirmed, this period would suggest that the donor star in IGR J17091-3624 has deviated from the standard main-sequence evolutionary path and is likely a (partially) stripped giant. In the optical band, no significant periodicity or correlation with the X-ray dips was detected, whereas the radio counterpart exhibited a flat to steep spectrum, in contrast to the inverted spectrum typically observed during the hard state of LMXBs. △ Less

Submitted 19 December, 2025; v1 submitted 24 August, 2025; originally announced August 2025.

Comments: 17 pages, 10 figures, 1 tables

Carbon-rich Sub-Neptune Interiors Are Compatible with JWST Observations

Authors: Zifan Lin, Sara Seager

Abstract: Many possible interior compositions exist for sub-Neptunes: ice-poor, ice-rich, and water-dominated interiors can all match the measured masses and radii. Motivated by recent theory of carbon-rich planet formation outside of the refractory organic carbon "soot line" and observations of carbon-rich protoplanetary disks around late M dwarfs, we propose another possible sub-Neptune composition: a car… ▽ More Many possible interior compositions exist for sub-Neptunes: ice-poor, ice-rich, and water-dominated interiors can all match the measured masses and radii. Motivated by recent theory of carbon-rich planet formation outside of the refractory organic carbon "soot line" and observations of carbon-rich protoplanetary disks around late M dwarfs, we propose another possible sub-Neptune composition: a carbon-rich composition consisting of an iron-silicate core, a carbon layer, and a hydrogen/helium-dominated envelope. We show that the interiors of three prototypical sub-Neptunes with high-quality spectral observations - TOI-270 d, GJ 1214 b, and K2-18 b - are consistent with carbon-rich compositions if they have $\leq100\times$ solar metallicity atmospheres. We further show that carbon-rich interiors lead to atmospheric compositions that match HST and JWST observations. Simulated carbon-rich TOI-270 d transmission spectra pass the $χ^2$ test under a wide range of C/O, haze, and cloud scenarios. K2-18 b spectral models are broadly consistent with observation, but requires additional sources for carbon species to be fully compatible. GJ 1214 b models, however, are incompatible with observations, ruling out a carbon-rich interior composition, if the atmosphere of the planet is primordial and reflects interior C/O. △ Less

Submitted 20 August, 2025; originally announced August 2025.

Comments: 15 pages, 10 figures, accepted for publication in the Astrophysical Journal Letters

Early Planet Formation in Embedded Disks (eDisk) XXII: Keplerian disk, disk structures and jets/outflows in the Class 0 protostar IRAS 04166+2706

Authors: Nguyen Thi Phuong, Chang Won Lee, John J. Tobin, Nagayoshi Ohashi, Jes K. Jørgensen, Shigehisa Takakuwa, Yuri Aikawa, Yusuke Aso, Zhi-Yun Li, Patrick M. Koch, Jonathan P. Williams, Sacha Gavino, Zhe-Yu Daniel Lin, Kengo Tomida, Woojin Kwon, Leslie W. Looney, Ilseung Han, Alejandro Santamarıa-Miranda, Shih-Ping Lai, Yen Hsi-Wei, Travis J. Thieme, Jinshi Sai, Christian Flores

Abstract: We present ALMA observations of the Class 0 protostar IRAS 04166+2706, obtained as part of the ALMA large program Early Planet Formation in Embedded Disks (eDisk). These observations were made in the 1.3 mm dust continuum and molecular lines at angular resolutions of $\sim 0.05''$ ($\sim 8$ au) and $\sim 0.16''$ ($\sim25$ au), respectively. The continuum emission shows a disk-like structure with a… ▽ More We present ALMA observations of the Class 0 protostar IRAS 04166+2706, obtained as part of the ALMA large program Early Planet Formation in Embedded Disks (eDisk). These observations were made in the 1.3 mm dust continuum and molecular lines at angular resolutions of $\sim 0.05''$ ($\sim 8$ au) and $\sim 0.16''$ ($\sim25$ au), respectively. The continuum emission shows a disk-like structure with a radius of $\sim22$ au. Kinematical analysis of $^{13}$CO(2-1), C$^{18}$O(2-1), H$_2$CO (3$_{0,3}$-2$_{0,2}$), CH$_3$OH (4$_2$-3$_1$) emission demonstrates that these molecular lines trace the infalling-rotating envelope and possibly a Keplerian disk, enabling us to estimate the protostar mass to be $0.15 \rm{M_\odot} < \rm{M_\star} < 0.39 M_\odot$. The dusty disk is found to exhibit a brightness asymmetry along its minor axis in the continuum emission, probably caused by a flared distribution of the dust and the high optical depth of the dust emission. In addition, the CO(2-1) and SiO(5-4) emissions show knotty and wiggling motions in the jets. Our high angular resolution observations revealed the most recent mass ejection events, which have occurred within the last $\sim 25$ years. △ Less

Submitted 10 August, 2025; originally announced August 2025.

Comments: Accepted for publication in ApJ

Planets Around Solar Twins/Analogs (PASTA) II: chemical abundances, systematic offsets, and clues to planet formation

Authors: Qinghui Sun, Chenyang Ji, Sharon Xuesong Wang, Zitao Lin, Johanna Teske, Yuan-Sen Ting, Megan Bedell, Fan Liu

Abstract: Context. Previous studies have suggested that the Sun is relatively depleted in refractory elements compared to other solar twins or analogs, potentially as a result of planet formation. However, such conclusions are often limited by inhomogeneous samples and a lack of direct comparison with stars known to host planets. Aims. We aim to perform a homogeneous and precise abundance analysis of sola… ▽ More Context. Previous studies have suggested that the Sun is relatively depleted in refractory elements compared to other solar twins or analogs, potentially as a result of planet formation. However, such conclusions are often limited by inhomogeneous samples and a lack of direct comparison with stars known to host planets. Aims. We aim to perform a homogeneous and precise abundance analysis of solar twins and analogs that host planets, to investigate possible chemical signatures associated with planet formation. Methods. We obtain high-resolution, high signal-to-noise ratio Magellan/MIKE spectra for 25 solar-like stars, including 22 confirmed or candidate planet hosts and three comparison stars. Stellar parameters and elemental abundances for 23 elements (from C to Eu) are derived through a strict line-by-line differential analysis relative to the Sun. Results. Our sample spans [Fe/H] = -0.23 to +0.18 dex and includes 20 solar analogs, six of which are solar twins. Typical abundance uncertainties range from 0.01 to 0.05 dex for lighter elements (e.g., Fe, Si, C, O, Na) and up to 0.1 dex for neutron-capture elements. The Sun is consistently depleted in refractory elements relative to all solar analogs and twins, regardless of planet type. Stars hosting small planets tentatively show slightly stronger refractory element depletion than those hosting giant planets, though the difference is not yet statistically significant. Conclusions. We emphasize the need for strictly differential, line-by-line analyses relative to the Sun, as well as careful consideration of systematic differences between instruments, to ensure consistency and the homogeneity required to achieve our goals. △ Less

Submitted 9 August, 2025; originally announced August 2025.

Comments: Main text has 9 pages, 3 figures, 4 tables; accepted for publication in A&A

Journal ref: A&A 701, A107 (2025)

Discovery and dynamics of a Sedna-like object with a perihelion of 66 au

Authors: Ying-Tung Chen, Patryk Sofia Lykawka, Yukun Huang, JJ Kavelaars, Wesley C. Fraser, Michele T. Bannister, Shiang-Yu Wang, Chan-Kao Chang, Matthew J. Lehner, Fumi Yoshida, Brett Gladman, Mike Alexandersen, Edward Ashton, Young-Jun Choi, A. Paula Granados Contreras, Takashi Ito, Youngmin JeongAhn, Jianghui Ji, Myung-Jin Kim, Samantha M. Lawler, Jian Li, Zhong-Yi Lin, Hong-Kyu Moon, Surhud More, Marco Muñoz-Gutiérrez , et al. (8 additional authors not shown)

Abstract: Trans-Neptunian objects (TNOs) with large perihelion distances ($q > 60$ au) and semi-major axes ($a > 200$ au) provide insights into the early evolution of the solar system and the existence of a hypothetical distant planet. These objects are still rare and their detection is challenging, yet they play a crucial role in constraining models of solar system formation. Here we report the discovery o… ▽ More Trans-Neptunian objects (TNOs) with large perihelion distances ($q > 60$ au) and semi-major axes ($a > 200$ au) provide insights into the early evolution of the solar system and the existence of a hypothetical distant planet. These objects are still rare and their detection is challenging, yet they play a crucial role in constraining models of solar system formation. Here we report the discovery of a Sedna-like TNO, 2023\,KQ$_{14}$, nicknamed `Ammonite', with $q = 66$ au, $a = 252$ au, and inclination $i=11^\circ$. Ammonite's orbit does not align with those of the other Sedna-like objects and fills the previously unexplained `$q$-gap' in the observed distribution of distant solar system objects. Simulations demonstrate that Ammonite is dynamically stable over 4.5 billion years. % with less than 1\% variation in its semi-major axis. Our analysis suggests that Ammonite and the other Sedna-like objects may have shared a primordial orbital clustering around 4.2 billion years ago. Furthermore, Ammonite's stable orbit favors larger orbits ($\sim$ 500 au) rather than closer ones for a large hypothetical planet in present-day trans-Neptunian space. △ Less

Submitted 4 August, 2025; originally announced August 2025.

Comments: Accepted manuscript of an article published open access in Nature Astronomy under a Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) license. The final published version is available at https://doi.org/10.1038/s41550-025-02595-7

Journal ref: Nature Astronomy, 2025

A fast radio burst from the first 3 billion years of the Universe

Authors: Manisha Caleb, Themiya Nanayakkara, Benjamin Stappers, Inés Pastor-Marazuela, Ilya S. Khrykin, Karl Glazebrook, Nicolas Tejos, J. Xavier Prochaska, Kaustubh Rajwade, Lluis Mas-Ribas, Laura N. Driessen, Wen-fai Fong, Alexa C. Gordon, Jordan Hoffmann, Clancy W. James, Fabian Jankowski, Lordrick Kahinga, Michael Kramer, Sunil Simha, Ewan D. Barr, Mechiel Christiaan Bezuidenhout, Xihan Deng, Zeren Lin, Lachlan Marnoch, Christopher D. Martin , et al. (3 additional authors not shown)

Abstract: Fast radio bursts (FRBs) are enigmatic millisecond-duration signals which encode otherwise unattainable information on the plasma which permeates our Universe, providing insights into magnetic fields and gas distributions. Here we report the discovery of FRB 20240304B originating at redshift 2.148 +/- 0.001 corresponding to just 3 billion years after the Big Bang. FRB 2024030 was detected with the… ▽ More Fast radio bursts (FRBs) are enigmatic millisecond-duration signals which encode otherwise unattainable information on the plasma which permeates our Universe, providing insights into magnetic fields and gas distributions. Here we report the discovery of FRB 20240304B originating at redshift 2.148 +/- 0.001 corresponding to just 3 billion years after the Big Bang. FRB 2024030 was detected with the MeerKAT radio telescope and localized to a low-mass, clumpy, star forming galaxy using the James Webb Space Telescope. This discovery doubles the redshift reach of localized FRBs and probes ionized baryons across ~80% of cosmic history. Its sightline, intersecting the Virgo Cluster and a foreground group, reveals magnetic field complexity over many gigaparsec scales. Our observations establish FRB activity during the peak of cosmic star formation and demonstrate that FRBs can probe galaxy formation during the most active era in cosmic time. △ Less

Submitted 3 August, 2025; originally announced August 2025.

Comments: 14 Pages, 3 Figures, 2 Tables

Detailed radial scale height profile of dust grains as probed by dust self-scattering in HL Tau

Authors: Haifeng Yang, Ian W. Stephens, Zhe-Yu Daniel Lin, Manuel Fernández-López, Zhi-Yun Li, Leslie W. Looney, Rachel Harrison

Abstract: The vertical settling of dust grains in a circumstellar disk, characterized by their scale height, is a pivotal process in the formation of planets. This study offers in-depth analysis and modeling of the radial scale height profile of dust grains in the HL Tau system, leveraging high-resolution polarization observations. We resolve the inner disk's polarization, revealing a significant near-far s… ▽ More The vertical settling of dust grains in a circumstellar disk, characterized by their scale height, is a pivotal process in the formation of planets. This study offers in-depth analysis and modeling of the radial scale height profile of dust grains in the HL Tau system, leveraging high-resolution polarization observations. We resolve the inner disk's polarization, revealing a significant near-far side asymmetry, with the near side being markedly brighter than the far side in polarized intensity. This asymmetry is attributed to a geometrically thick inner dust disk, suggesting a large aspect ratio of $H/R \ge 0.15$. The first ring at 20 au exhibits an azimuthal contrast, with polarization enhanced along the minor axis, indicating a moderately thick dust ring with $H/R \approx 0.1$. The absence of the near-far side asymmetry at larger scales implies a thin dust layer, with $H/R < 0.05$. Taken together, these findings depict a disk with a turbulent inner region and a settled outer disk, requiring a variable turbulence model with $α$ increasing from $10^{-5}$ at 100 au to $10^{-2.5}$ at 20 au. This research sheds light on dust settling and turbulence levels within protoplanetary disks, providing valuable insights into the mechanisms of planet formation. △ Less

Submitted 2 August, 2025; originally announced August 2025.

Comments: 10 pages, 7 figures, and accepted for publication in AAS journals

Delayed Launch of Ultrafast Outflows in the Tidal Disruption Event AT2020afhd

Authors: Zikun Lin, Yanan Wang, De-Fu Bu, Junjie Mao, Jifeng Liu

Abstract: We report the detection and characterization of ultrafast outflows (UFOs) in the X-ray spectra of the tidal disruption event (TDE) AT2020afhd, based on observations from NICER, Swift, and XMM. Prominent blueshifted absorption features were detected exclusively during the intermediate phase of the event, occurring between days 172 and 212 within the first 300 days post-discovery. During this period… ▽ More We report the detection and characterization of ultrafast outflows (UFOs) in the X-ray spectra of the tidal disruption event (TDE) AT2020afhd, based on observations from NICER, Swift, and XMM. Prominent blueshifted absorption features were detected exclusively during the intermediate phase of the event, occurring between days 172 and 212 within the first 300 days post-discovery. During this period, the UFO appeared no earlier than day 74, strengthened between days 172 and 194, and disappeared after day 215. This marks the first time that the full evolutionary sequence of X-ray outflows has been observed in a TDE. Moreover, the outflows exhibited a dramatic deceleration from ~0.19c to ~0.0097c over a span of approximately 10 days. Photoionization spectral analysis reveals an inverse correlation between outflow velocity and ionization parameter, in contradiction to the predictions from radiation pressure-driven wind. Eventually, we propose that the delayed onset of the outflows may result from an increase in the wind opening angle and/or metal enrichment, particularly iron and oxygen, during the disk formation phase. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: 15 pages, 7 figures, 4 tables; accepted for publication in ApJ Letters

Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?

Authors: Huaqing Cheng, Qingchang Zhao, L. Tao, H. Feng, F. Coti Zelati, H. W. Pan, A. L. Wang, Y. N. Wang, M. Y. Ge, A. Rau, A. Marino, L. Zhang, W. J. Zhang, F. Carotenuto, L. Ji, C. C. Jin, D. Y. Li, B. F. Liu, Y. Liu, E. L. Qiao, N. Rea, R. Soria, S. Wang, Z. Yan, W. Yuan , et al. (56 additional authors not shown)

Abstract: Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in… ▽ More Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in the X-ray band. In this Letter, we present the discovery of an intriguing X-ray transient, EP J182730.0-095633, via the Einstein Probe (EP) and subsequent multi-wavelength follow-up studies. This transient, located on the Galactic plane, experienced a faint and brief X-ray outburst lasting about 20 days. Its X-ray spectrum is non-thermal and consistent with a power-law model with a nearly constant photon index of $Γ\sim2$ throughout the outburst. A long-lasting millihertz quasi-periodic oscillation (QPO) signal was detected in its X-ray light curve, centered around a frequency of $\sim0.04$ Hz. A transient near-infrared source was identified as its counterpart, although no optical emission was detectable, likely due to significant extinction. A radio counterpart was also observed, displaying an inverted radio spectrum with $α\sim0.45$. The X-ray spectral and temporal characteristics, along with the multi-wavelength properties, indicate that the source is a faint low-mass X-ray binary, with the compact object likely being a black hole. This work demonstrates the potential of the EP in discovering new X-ray binaries by capturing faint-level X-ray outbursts. △ Less

Submitted 17 July, 2025; originally announced July 2025.

Comments: 22 pages, 5 figures (plus 3 in appendix), 3 tables in appendix. Accepted for publication in ApJ Letters

A New Brown Dwarf Orbiting an M star and An Investigation on the Eccentricity Distribution of Transiting Long-Period Brown Dwarfs

Authors: Tianjun Gan, Charles Cadieux, Shigeru Ida, Sharon X. Wang, Shude Mao, Zitao Lin, Keivan G. Stassun, Adam J. Burgasser, Steve B. Howell, Catherine A. Clark, Ivan A. Strakhov, Paul Benni, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Luc Arnold, Étienne Artigau, David Charbonneau, Karen A. Collins, Neil J. Cook, Zoë L. de Beurs, Sarah J. Deveny , et al. (10 additional authors not shown)

Abstract: The orbital eccentricities of brown dwarfs encode valuable information of their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575b, a long-period, massive brown dwarf orbiting a low-mass M5V star ($\rm 0.21\pm0.02\,M_\odot$) delivered by the TESS mission. The companion has a mass and radius of… ▽ More The orbital eccentricities of brown dwarfs encode valuable information of their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575b, a long-period, massive brown dwarf orbiting a low-mass M5V star ($\rm 0.21\pm0.02\,M_\odot$) delivered by the TESS mission. The companion has a mass and radius of $\rm 72.4\pm4.1\,M_J$ and $\rm 0.84\pm0.07\,R_J$ on a 32-day moderately eccentric orbit ($e=0.187\pm0.002$), making it the third highest-mass-ratio transiting brown dwarf system known to date. Building on this discovery, we investigate the eccentricity distributions of a sample of transiting long-period ($10\leq P\lesssim 1000$ days, $\sim$0.1-1.5 AU) giant planets, brown dwarfs and low-mass stars. We find that brown dwarfs exhibit an eccentricity behavior nearly identical to that of giant planets: a preference for circular orbits with a long tail toward high eccentricities. Such a trend contrasts sharply with direct imaging findings, where cold (5-100 AU) brown dwarfs and giant planets display distinct eccentricity distributions. Our results suggest that transiting long-period brown dwarfs and giant planets probably 1) form in different routes at exterior orbits but undergo analogous dynamical evolution processes and migrate inwards; or 2) both contain two sub-groups, one with widely spread eccentricities while the other has circular orbits, that jointly sculpt the eccentricity distributions. The low-mass-star systems appear to be a distinctive population, showing a peak eccentricity at about 0.3, akin to more massive stellar binaries. △ Less

Submitted 12 July, 2025; originally announced July 2025.

Comments: 18 pages, 8 figures, 4 tables, accepted for publication in ApJL

Insights from the "Red devil" AT 2022fpx: A Dust-reddened Family of Tidal Disruption Events Excluded by Their Apparent Red Color?

Authors: Zheyu Lin, Ning Jiang, Yibo Wang, Xu Kong, Shifeng Huang, Zesen Lin, Chen Qin, Tianyu Xia

Abstract: We report unnoticed but intriguing features in the peculiar nuclear transient AT 2022fpx, and investigate its type. These features include the constantly red optical color of $g-r>0$, a stable soft X-ray flare ($kT\sim100$ eV) in the past $\sim$550 days, a prominent mid-infrared echo peaked at $\sim$$10^{43.3}$ erg s$^{-1}$ and the confirmation of a weak active galactic nucleus by weak flares in p… ▽ More We report unnoticed but intriguing features in the peculiar nuclear transient AT 2022fpx, and investigate its type. These features include the constantly red optical color of $g-r>0$, a stable soft X-ray flare ($kT\sim100$ eV) in the past $\sim$550 days, a prominent mid-infrared echo peaked at $\sim$$10^{43.3}$ erg s$^{-1}$ and the confirmation of a weak active galactic nucleus by weak flares in pre-event Wide-field Infrared Survey Explorer mid-infrared light curves with no contemporary optical, radio or X-ray counterparts. The combination of the optical red color and possible origin of a tidal disruption event (TDE) of AT 2022fpx is particularly attractive, as it challenges the most widely accepted and adopted "blue color" criterion for optical TDE selection. Although we still cannot confirm whether the red color is intrinsic, we do find that the "blue color" criterion can filter out normal TDEs whose optical-UV spectral energy distributions (SEDs) are either severely contaminated by prominent emission lines (especially H$α$) or heavily dust-reddened. Hence, its potential selection effect may have been imprinted on the whole optical TDE family. Blackbody fitting on the optical (rest-frame $\sim$$4000-7000$ Å) and optical-UV ($\sim$$2000-7000$ Å) SEDs of four TDEs with high-cadence UV observations shows that $T_\mathrm{bb}$ rise by $\sim$40$-$110 \% when the UV bands are included. The power-law models ($f_λ\proptoλ^{-α}$ with $α=2-3$) can fit the rest-frame $\sim$$2000-7000$ ÅSEDs more consistently, indicating that SEDs should peak at shorter wavelengths, but not simple blackbodies. Hence, the estimated released energy for the optical-UV bright but X-ray faint TDEs based on blackbody SED fitting should be significantly lower than the intrinsic energy. △ Less

Submitted 5 September, 2025; v1 submitted 7 July, 2025; originally announced July 2025.

Comments: 22 pages, 10 figures, 3 tables, accepted by ApJ

Journal ref: ApJ 990 22 (2025)

Introduction to the Chinese Space Station Survey Telescope (CSST)

Authors: CSST Collaboration, Yan Gong, Haitao Miao, Hu Zhan, Zhao-Yu Li, Jinyi Shangguan, Haining Li, Chao Liu, Xuefei Chen, Haibo Yuan, Jilin Zhou, Hui-Gen Liu, Cong Yu, Jianghui Ji, Zhaoxiang Qi, Jiacheng Liu, Zigao Dai, Xiaofeng Wang, Zhenya Zheng, Lei Hao, Jiangpei Dou, Yiping Ao, Zhenhui Lin, Kun Zhang, Wei Wang , et al. (97 additional authors not shown)

Abstract: The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific inst… ▽ More The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e. Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential. △ Less

Submitted 19 September, 2025; v1 submitted 6 July, 2025; originally announced July 2025.

Comments: 48 pages, 12 figures, 1 table. Accepted for publication in SCIENCE CHINA Physics, Mechanics & Astronomy

Recurring region for neutron-star observables

Authors: Alexander Clevinger, Zidu Lin, Milena Albino, Peter Hammond, Veronica Dexheimer, Andrew Steiner

Abstract: In this letter, we report a new phenomena of recurring regions when relating observables for hybrid neutron stars and hybrid neutron-star mergers. To describe dense matter within hybrid stars, we introduce a percolation to vary the size and characteristics of the deconfinement phase transition to quark matter. Before and after the percolation, we keep the hadronic and quark phases the same, descri… ▽ More In this letter, we report a new phenomena of recurring regions when relating observables for hybrid neutron stars and hybrid neutron-star mergers. To describe dense matter within hybrid stars, we introduce a percolation to vary the size and characteristics of the deconfinement phase transition to quark matter. Before and after the percolation, we keep the hadronic and quark phases the same, described by different realistic models for the equation of state of beta-equilibrated, charge-neutral, zero-temperature matter. When solving spherical and deformed equations for neutron stars in general relativity, we find that: no matter the size or characteristics of the percolation region, or the order of the phase transition on either side (hadronic and quark), as long as we minimize the average sound speed from the beginning of the percolation region to the central density for a given star, we can produce equations of state that cross through the same, small recurring region within mass-radius and mass-tidal deformability diagrams. Our findings provide a new way to produce hybrid equations of state for dense matter that match a given observation of neutron stars or neutron star mergers. △ Less

Submitted 30 June, 2025; originally announced June 2025.

Unveiling the nature and fate of the almost-dark cloud AGC 226178 through HI mapping

Authors: Yu-Zhu Sun, Hong-Xin Zhang, Elias Brinks, Rory Smith, Fujia Li, Minsu Kim, Se-Heon Oh, Zesen Lin, Jaebeom Kim, Weibin Sun, Tie Li, Patrick Côté, Alessandro Boselli, Lijun Chen, Pierre-Alain Duc, Sanjaya Paudel, Matthew A. Taylor, Kaixiang Wang, Enci Wang, Lanyue Zhang, Yinghe Zhao

Abstract: The origin of extragalactic, almost dark HI clouds with extreme gas-to-stellar mass ratios remains poorly understood. We investigate the nature and fate of the "almost dark" cloud AGC 226178, projected within the Virgo cluster, with an HI-to-stellar mass ratio of ~1000. We present deep single-dish HI mapping from the Five-hundred-meter Aperture Spherical Telescope (FAST), complemented by high-reso… ▽ More The origin of extragalactic, almost dark HI clouds with extreme gas-to-stellar mass ratios remains poorly understood. We investigate the nature and fate of the "almost dark" cloud AGC 226178, projected within the Virgo cluster, with an HI-to-stellar mass ratio of ~1000. We present deep single-dish HI mapping from the Five-hundred-meter Aperture Spherical Telescope (FAST), complemented by high-resolution interferometric data from the Very Large Array (VLA), as part of the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) project. These observations provide the highest-quality HI analysis to date of such a cloud, combining resolution and sensitivity. FAST data reveal a short, low-velocity tail toward the dwarf galaxy VCC 2034, previously proposed as a possible origin for AGC 226178. However, VCC 2034 shows a line-of-sight asymmetric HI feature and cometary morphology indicating a stripping event unrelated to AGC 226178. VLA data reveal a velocity gradient across AGC 226178 and a clumpy internal structure. The velocity dispersion exceeds the thermal linewidth, implying turbulence or unresolved motions. The cloud cannot be gravitationally bound by atomic gas alone. The resolved HI clumps follow standard HI mass-star formation rate and mass-size relations, with those forming stars reaching surface densities above the threshold for self-shielding. We conclude that AGC 226178 is a free-floating HI cloud of unknown origin. The system appears to be in the process of disintegration. It is likely located well outside the Virgo cluster, as the preservation of its extended HI morphology within the cluster environment would otherwise require a substantial reservoir of unseen molecular gas with a mass exceeding that of the observed HI content. While confinement pressure from the hot intracluster medium may aid its stability, it is unlikely to be the dominant factor preventing its disruption. △ Less

Submitted 31 July, 2025; v1 submitted 29 June, 2025; originally announced June 2025.

Comments: 18 pages, 14 figures. Accepted for Publication in A&A

Journal ref: A&A 701, A73 (2025)

Early Planet Formation in Embedded Disks (eDisk) XVII: A Compact but Structured Keplerian Disk and Large-scale Streamers Revealed in the Class I Protostellar System IRAS 04169+2702

Authors: Ilseung Han, Woojin Kwon, Yusuke Aso, Nagayoshi Ohashi, John J. Tobin, Jes K. Jørgensen, Shigehisa Takakuwa, Leslie W. Looney, Yuri Aikawa, Christian Flores, Itziar de Gregorio-Monsalvo, Patrick M. Koch, Chang Won Lee, Jeong-Eun Lee, Zhi-Yun Li, Zhe-Yu Daniel Lin, Jinshi Sai, Travis J. Thieme, Jonathan P. Williams, Sacha Gavino, Miyu Kido, Shih-Ping Lai, Nguyen Thi Phuong, Alejandro Santamaría-Miranda, Hsi-Wei Yen

Abstract: We present high-resolution ($\sim$0.05"; 8 au) dust continuum and molecular line observations toward the Class I protostellar system IRAS 04169+2702 in the Taurus B213 region, as part of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk). The 1.3-mm dust continuum emission traces a circumstellar disk with a central depression toward the protostar. Our VLA observations of the s… ▽ More We present high-resolution ($\sim$0.05"; 8 au) dust continuum and molecular line observations toward the Class I protostellar system IRAS 04169+2702 in the Taurus B213 region, as part of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk). The 1.3-mm dust continuum emission traces a circumstellar disk with a central depression toward the protostar. Our VLA observations of the same target reveal a single central peak dominated by the free-free emission, which coincides with the depression of the thermal dust emission. The mean spectral index of the thermal dust emission from 1.3 mm to 1.4 cm is approximately 2.8, suggestive of the presence of grains grown to millimeter or centimeter sizes in the disk. Velocity gradients along the disk major axis are seen in emission from $^{12}$CO (2-1), $^{13}$CO (2-1), and C$^{18}$O (2-1) molecular lines. The position-velocity diagrams of these lines unveil a Keplerian-rotating disk with a radius of $\sim$21 au around a 1.3 $M_{\odot}$ protostar, as well as an infalling and rotating envelope with the angular momentum conserved. In addition to the compact disk, large-scale infalling spiral structures extending up to approximately 1400 au, streamers, are discovered in C$^{18}$O (2-1), SO (6$_5$-5$_4$), and H$_2$CO (3$_{0, 3}$-2$_{0, 2}$) as well as in the 1.3-mm continuum emission. Notably, in the region closer to the protostar, the spatial coincidence of C$^{18}$O and SO may indicate the presence of a shock related to accretion through the spiral arms. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ

AVID: Formation and evolution of a coalesced major merger of late-type dwarf galaxies (VCC 479) on the outskirts of the Virgo cluster

Authors: Weibin Sun, Hong-Xin Zhang, Rory Smith, Elias Brinks, Patrick Côté, Se-Heon Oh, Zesen Lin, Alessandro Boselli, Laura Ferrarese, Fujia Li, Yuzhu Sun, Lijun Chen, Lanyue Zhang, Minsu Kim, Jaebeom Kim, Tie Li, Bojun Tao, Matt Taylor, Pierre-Alain Duc, Ruben Sánchez-Janssén, Yinghe Zhao, Sanjaya Paudel, Eric W. Peng, Kaixiang Wang, Stephen Gwyn , et al. (2 additional authors not shown)

Abstract: Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galax… ▽ More Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galaxy interactions and environmental processes, and understanding its relevance to the diversity of dwarf galaxies in cluster environments. Our analysis is based on VLA and FAST HI emission line mapping from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) survey. We also perform idealized hydrodynamical simulations of dwarf-dwarf mergers to help interpret the observations. We identify symmetric stellar shell structures in VCC 479, indicative of a coalesced major merger of dwarf galaxies. The galaxy features a central starburst, initiated $\sim$600 Myr ago, embedded within an exponential disk quenched $\sim$1 Gyr ago. The starburst contributes only 2.9$\pm$0.5\% of the total stellar mass, and VCC 479's global star formation rate is 0.3 dex lower than typical dwarfs of similar mass. The galaxy is highly HI deficient, with most HI gas concentrated within the central 1 kpc and little extended HI envelope. The misalignment of the HI velocity field with the stellar body is best explained by merger-triggered gas inflow, as seen in our simulations. Our analysis is consistent with a scenario that the majority of HI gas of the progenitor galaxies was removed by the cluster environment prior to the final coalescence. The merger concentrates the remaining gas toward the galaxy center, triggering a central starburst. The combined effect of environment stripping and galaxy merger has transformed VCC 479 into a blue-core dwarf undergoing morphological transition from a late-type to an early-type galaxy. △ Less

Submitted 6 July, 2025; v1 submitted 18 June, 2025; originally announced June 2025.

Comments: 18 pages, 15 figures. Accepted for Publication in A&A

Journal ref: A&A 700, A113 (2025)

Unveiling the Cosmic Dance of Repeated Nuclear Transient ASASSN-14ko: Insights from Multiwavelength Observations

Authors: Shifeng Huang, Tinggui Wang, Ning Jiang, Rong-Feng Shen, Zhaohao Chen, Yuanming Wang, Jiazheng Zhu, Yibo Wang, Yunguo Jiang, Xinwen Shu, Hucheng Ding, Xiongjun Fang, Yifan Wang, Jie Lin, Jingran Xu, Xu Chen, Zheyu Lin, Zhengfeng Sheng

Abstract: ASASSN-14ko is a periodically repeating nuclear transient. We conducted high-cadence, multiwavelength observations of this source, revealing several recurrent early bumps and rebrightenings in its UV/optical light curves. The energy released during these bumps and rebrightenings shows a diminishing trend in recent UV/optical outbursts, which we monitored through multiwavelength observations. These… ▽ More ASASSN-14ko is a periodically repeating nuclear transient. We conducted high-cadence, multiwavelength observations of this source, revealing several recurrent early bumps and rebrightenings in its UV/optical light curves. The energy released during these bumps and rebrightenings shows a diminishing trend in recent UV/optical outbursts, which we monitored through multiwavelength observations. These features can be ascribed to the interaction between stream debris and the expanded disk in the repeated partial tidal disruption event. The X-ray light curve exhibits an inverse pattern compared to the UV/optical bands, displaying sporadic outbursts. Furthermore, our observations demonstrate that the blackbody temperature and radius in each outburst increase with the UV/optical luminosity, and such evolution resembles that observed in X-ray quasiperiodic eruptions, whereas distinguishing it from typical tidal disruption events. △ Less

Submitted 17 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ, 16 pages, 10 figures

Magnetic Fields in the Pillars of Creation

Authors: Adwitiya Sarkar, Leslie W. Looney, Marc W. Pound, Zhi-Yun Li, Ian W. Stephens, Manuel Fernandez Lopez, Simon Coude, Zhe-Yu Daniel Lin, Haifeng Yang, Reid Faistl

Abstract: Due to dust grain alignment with magnetic fields, dust polarization observations of far-infrared emission from cold molecular clouds are often used to trace magnetic fields, allowing a probe of the effects of magnetic fields on the star formation process. We present inferred magnetic field maps of the Pillars of Creation region within the larger M16 emission nebula, derived from dust polarization… ▽ More Due to dust grain alignment with magnetic fields, dust polarization observations of far-infrared emission from cold molecular clouds are often used to trace magnetic fields, allowing a probe of the effects of magnetic fields on the star formation process. We present inferred magnetic field maps of the Pillars of Creation region within the larger M16 emission nebula, derived from dust polarization data in the 89 and 154 micron continuum using SOFIA/HAWC+. We derive magnetic field strength estimates using the Davis-Chandrasekhar-Fermi method. We compare the polarization and magnetic field strengths to column densities and dust continuum intensities across the region to build a coherent picture of the relationship between star forming activity and magnetic fields in the region. The projected magnetic field strengths derived are in the range of 50-130 microGauss, which is typical for clouds of similar n(H2), i.e., molecular hydrogen volume density on the order of 10^4-10^5 cm^(-3). We conclude that star formation occurs in the finger tips when the magnetic fields are too weak to prevent radial collapse due to gravity but strong enough to oppose OB stellar radiation pressure, while in the base of the fingers the magnetic fields hinder mass accretion and consequently star formation. We also support an initial weak field model (<50 microGauss) with subsequent strengthening through realignment and compression, resulting in a dynamically important magnetic field. △ Less

Submitted 17 June, 2025; originally announced June 2025.

Comments: 16 pages, 9 figures, accepted for publication in ApJ

MatBYIB: A Matlab-based code for Bayesian inference of extreme mass-ratio inspiral binary with arbitrary eccentricity

Authors: Gen-Liang Li, Shu-Jie Zhao, Huai-Ke Guo, Jing-Yu Su, Zhen-Heng Lin

Abstract: Accurate parameter estimation(PE) of gravitational waves(GW) is essential for GW data analysis. In extreme mass-ratio inspiral binary(EMRI) systems, orbital eccentricity is a critical parameter for PE. However, current software for for PE of GW often neglects the direct estimation of orbital eccentricity. To fill this gap, we have developed the MatBYIB, a MATLAB-based software package for PE of GW… ▽ More Accurate parameter estimation(PE) of gravitational waves(GW) is essential for GW data analysis. In extreme mass-ratio inspiral binary(EMRI) systems, orbital eccentricity is a critical parameter for PE. However, current software for for PE of GW often neglects the direct estimation of orbital eccentricity. To fill this gap, we have developed the MatBYIB, a MATLAB-based software package for PE of GW with arbitrary eccentricity. The MatBYIB employs the Analytical Kludge (AK) waveform as a computationally efficient signal generator and computes parameter uncertainties via the Fisher Information Matrix (FIM) and the Markov Chain Monte Carlo (MCMC). For Bayesian inference, we implement the Metropolis-Hastings (M-H) algorithm to derive posterior distributions. To guarantee convergence, the Gelman-Rubin convergence criterion (the Potential Scale Reduction Factor R) is used to determine sampling adequacy, with MatBYIB dynamically increasing the sample size until R < 1.05 for all parameters. Our results demonstrate strong agreement between FIM- based predictions and full MCMC sampling. This program is user-friendly and allows for estimation of gravitational wave parameters with arbitrary eccentricity on standard personal computers. Code availability:The implementation is open-source at https://github.com/GenliangLi/MatBYIB. △ Less

Submitted 15 November, 2025; v1 submitted 6 June, 2025; originally announced June 2025.

Comments: 11 pages, 6 figures

Journal ref: Universe 2025, 11(8), 259

Bayesian Inference of the Landau Parameter $G'_0$ from Joint Gamow-Teller Measurements

Authors: Zidu Lin, Gianluca Colò, A. W. Steiner, Amber Stinson

Abstract: The Landau-Migdal parameter $G'_0$ characterizes the main part of the spin-isospin nucleon-nucleon interaction. Consequently, the $G'_0$ is closely related to the Gamow-Teller resonance (GTR), the beta and double-beta decay rates of finite nuclei, the spin response of hot and dense nucleonic matter that determines the neutrino-nucleon reaction rates in core-collapse supernovae (CCSNe) and binary n… ▽ More The Landau-Migdal parameter $G'_0$ characterizes the main part of the spin-isospin nucleon-nucleon interaction. Consequently, the $G'_0$ is closely related to the Gamow-Teller resonance (GTR), the beta and double-beta decay rates of finite nuclei, the spin response of hot and dense nucleonic matter that determines the neutrino-nucleon reaction rates in core-collapse supernovae (CCSNe) and binary neutron star (BNS) mergers, and finally the critical density for pion condensation in neutron stars. Historically, the $G'_0$ was obtained by fitting the peak location of experimental GTR spectra by using phenomenological pion exchange models, without strict uncertainty quantification. In this letter, for the first time, we report the Bayesian inference of $G'_0$ by using a self-consistent Skyrme Quasiparticle Random Phase Approximation (QRPA) model and joint constraints from experimental GTR measurements on $^{208}\mathrm{Pb}$, $^{132}\mathrm{Sn}$, $^{90}\mathrm{Zr}$. Our extracted $G_0'$ is $0.48\pm0.034$, which is close to the prediction of a few existing Skyrme models that consider the spin-isospin observables but is smaller than the extracted ones from pion-exchange models. We hint to possible reasons for this deviation, like the value of the nucleon effective mass $\frac{m^*}{m}$. Finally, we demonstrate the influence of $G'_0$ on neutrino opacities in CCSNe and BNS mergers. The new Skyrme parameterizations from our Bayesian study may also be used to study other spin-isospin-dependent phenomena. △ Less

Submitted 9 June, 2025; v1 submitted 5 June, 2025; originally announced June 2025.

Comments: the spelling of an author's name is corrected in v2

The $M_{\rm BH}-M_\star$ Relation of the hyperluminous Dust-obscured Quasars up to $z \sim 4$

Authors: Yibin Luo, Lulu Fan, Weibin Sun, Haoran Yu, Yunkun Han, Guangwen Chen, Mengqiu Huang, Yihang Zhang, Zheyu Lin

Abstract: Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows only a small amount of scattered light from the obscured quasar to escape, enabling the decomposition of the stellar component from the total flux. The presence of scattered li… ▽ More Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows only a small amount of scattered light from the obscured quasar to escape, enabling the decomposition of the stellar component from the total flux. The presence of scattered light enables the redshift of the source and the properties of the black hole to be obtained from SDSS and SDSS-related literature. From WISE and SDSS data, we select 11 hyperluminous Hot DOGs at $z=1.5-3.7$ with bolometric luminosities $L_{\rm bol} \gtrsim 10^{47}\,\mathrm{erg \ s^{-1}}$. We investigate the $M_{\rm BH}-M_\star$ relation in these sources using Bayesian spectral energy distribution (SED) fitting or with extra constraints from \textit{Hubble Space Telescope} (HST) image decomposition. Stellar masses are successfully derived for eight Hot DOGs. We find high Eddington ratios $λ_{\rm Edd}$ in these Hot DOGs, with the median value of 1.05 and the maximum value close to 3. The super-Eddington accretion may be associated with the overdense environments of Hot DOGs. We find no significant differences in the $M_{\rm BH}/M_\star$ of these Hot DOGs compared to the local relation, suggesting that these dust-obscured quasars are the progenitors of massive early-type galaxies. We speculate that the subsequent evolution of Hot DOGs may be significantly influenced by AGN feedback and remain on the local relation. △ Less

Submitted 1 June, 2025; originally announced June 2025.

Comments: 14 pages, 5 figures, Accepted for pubulication in AAS journal

Journal ref: 2025, ApJ, 986, 195

The Mini-SiTian Array: first-two-year operation

Authors: Min He, Hong Wu, Liang Ge, Jian-feng Tian, Zheng Wang, Hai-yang Mu, Yu Zhang, Yang Huang, Jie Zheng, Zhou Fan, Zheng-yang Li, Hong-hui Gu, Heng-geng Han, Kai Xiao, Zhi-rui Li, Jun-jie Jin, Bei-chuan Wang, Jun Ma, Jin-hang Zou, Ying Wu, Jiu-peng Guo, Li-guo Fang, Zhi-gang Hou, Bo-wen Zhang, Yun-fei Xu , et al. (48 additional authors not shown)

Abstract: The SiTian project, designed to utilize 60 telescopes distributed across multiple sites in China, is a next-generation time-domain survey initiative. As a pathfinder for the SiTian project, the Mini-SiTian (MST) has been proposed and implemented to test the SiTian's brain and data pipeline, and to evaluate the feasibility of its technology and science cases. Mounted at the Xinglong Observatory, th… ▽ More The SiTian project, designed to utilize 60 telescopes distributed across multiple sites in China, is a next-generation time-domain survey initiative. As a pathfinder for the SiTian project, the Mini-SiTian (MST) has been proposed and implemented to test the SiTian's brain and data pipeline, and to evaluate the feasibility of its technology and science cases. Mounted at the Xinglong Observatory, the MST project comprises three 30 cm telescopes and has been operated since Nov. 2022. Each telescope of the MST possesses a large field of view, covering $2.29^{\circ}$ $\times$ $1.53^{\circ}$ FOV, and is equipped with $g'$, $r'$ and $i'$ filters, respectively. Acting as the pioneer of the forthcoming SiTian project, the MST is dedicated to the discovery of variable stars, transients, and outburst events, and has already obtained some interesting scientific results. In this paper, we will summarize the first-two-year operation of the MST project. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 10 pages, 11 figures, Accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array

L1448 IRS3B: Dust Polarization Aligned with Spiral Features, Tracing Gas Flows

Authors: Leslie W. Looney, Zhe-Yu Daniel Lin, Zhi-Yun Li, John J. Tobin, Martin Radecki, Syzygy Butte, Ian W. Stephens, Manuel Fernandez-Lopez, Haifeng Yang, Nickalas K. Reynolds, Patrick Sheehan, Woojin Kwon, Rachel Harrison, Allen North

Abstract: Circumstellar disk dust polarization in the (sub)millimeter is, for the most part, not from dust grain alignment with magnetic fields but rather indicative of a combination of dust self-scattering with a yet unknown alignment mechanism that is consistent with mechanical alignment. While the observational evidence for scattering has been well established, that for mechanical alignment is less so. C… ▽ More Circumstellar disk dust polarization in the (sub)millimeter is, for the most part, not from dust grain alignment with magnetic fields but rather indicative of a combination of dust self-scattering with a yet unknown alignment mechanism that is consistent with mechanical alignment. While the observational evidence for scattering has been well established, that for mechanical alignment is less so. Circum-multiple dust structures in protostellar systems provide a unique environment to probe different polarization alignment mechanisms. We present ALMA Band 4 and Band 7 polarization observations toward the multiple young system L1448 IRS3B. The polarization in the two Bands is consistent with each other, presenting multiple polarization morphologies. On the size scale of the inner envelope surrounding the circum-multiple disk, the polarization is consistent with magnetic field dust grain alignment. On the very small scale of compact circumstellar regions, we see polarization that is consistent with scattering around source a and c, which are likely the most optically thick components. Finally, we see polarization that is consistent with mechanical alignment of dust grains along the spiral dust structures, which would suggest that the dust is tracing the relative gas flow along the spiral arms. If the gas-flow dust grain alignment mechanism is dominant in these cases, disk dust polarization may provide a direct probe of the small-scale kinematics of the gas flow relative to the dust grains. △ Less

Submitted 10 March, 2025; originally announced March 2025.

Comments: ApJ accepted, 23 pages, 16 Figures

Calibrating the Color-Magnitude Relation of M Giants by Using Open Clusters

Authors: Xiaoyu Tang, Chaojie Hao, Jing Li, Zhengzhou Yan, Ye Xu, Jing Zhong, Zehao Lin, Yingjie Li, Dejian Liu, Longfei Ding, Xiaofang Long

Abstract: M giants, with their distinctive properties such as high luminosity, serve as excellent indicators for mapping the structure of the Milky Way. The distance to distant M giants can be determined by using the color-magnitude relation (CMR), which is derived from color-magnitude diagrams of specific systems in previous studies. In this work, we aimed to achieve more accurate distance determination fo… ▽ More M giants, with their distinctive properties such as high luminosity, serve as excellent indicators for mapping the structure of the Milky Way. The distance to distant M giants can be determined by using the color-magnitude relation (CMR), which is derived from color-magnitude diagrams of specific systems in previous studies. In this work, we aimed to achieve more accurate distance determination for M giants by focusing on open clusters (OCs) with a large number of member stars and thus improve the CMR. For the first time, we compiled a census of OCs harboring M giants using Gaia Data Release 3 (DR3) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope Data Release 9. We identified 58 M giants associated with 43 OCs and obtained their astrometric and photometric parameters from Gaia DR3. Using the distances of these OCs, we derived the CMR for M giants as a linear correlation, expressed as $M_{Ks}=3.85-8.26(J-K_s$). This linear relation proved superior to the empirical distance relation in characterizing the CMR of M giants. The photometric distances of M giants derived from the CMR are consistent with the parallax distances from Gaia and known spectroscopic distances, with median deviations of 1.5% and 2.3%, respectively. Using the distances of M giants derived from the CMR, we computed their radial velocity ($V_R$), azimuthal velocity ($Vφ$), and vertical velocity ($V_Z$), respectively. The distributions of these velocities revealed key features of the Galactic disk, including oscillation, north-south rotational asymmetry, and warp. These findings are consistent with previous studies and further validate the reliability of the derived CMR. △ Less

Submitted 28 February, 2025; originally announced February 2025.

Journal ref: The Astrophysical Journal Supplement Series, 276:63 (17pp),2025 February

Towards constraining QCD phase transitions in neutron star interiors: Bayesian Inference with TOV linear response analysis

Authors: Ronghao Li, Sophia Han, Zidu Lin, Lingxiao Wang, Kai Zhou, Shuzhe Shi

Abstract: The potential hadron-to-quark phase transition in neutron stars has not been fully understood as the property of cold, dense, and strongly interacting matter cannot be theoretically described by the first-principle perturbative calculations, nor have they been systematically measured through terrestrial low-to-intermediate energy heavy-ion experiments. Given the Tolman--Oppenheimer--Volkoff (TOV)… ▽ More The potential hadron-to-quark phase transition in neutron stars has not been fully understood as the property of cold, dense, and strongly interacting matter cannot be theoretically described by the first-principle perturbative calculations, nor have they been systematically measured through terrestrial low-to-intermediate energy heavy-ion experiments. Given the Tolman--Oppenheimer--Volkoff (TOV) equations, the equation of state (EoS) of the neutron star (NS) matter can be constrained by the observations of NS mass, radius, and tidal deformability. However, large observational uncertainties and the limited number of observations currently make it challenging to strictly reconstruct the EoS, especially to identify interesting features such as a strong first-order phase transition. In this work, we study the dependency of reconstruction quality of the phase transition on the number of NS observations of mass and radius as well as their uncertainty, based on a fiducial EoS. We conquer this challenging problem by constructing a neural network, which allows one to parametrize the EoS with minimum model-dependency, and by devising an algorithm of parameter optimization based on the analytical linear response analysis of the TOV equations. This work may pave the way for the understanding of the phase transition features in NSs using future $x$-ray and gravitational wave measurements. △ Less

Submitted 29 April, 2025; v1 submitted 27 January, 2025; originally announced January 2025.

Comments: The data for the plots are openly available: https://doi.org/10.5281/zenodo.15086456

Report number: RIKEN-iTHEMS-Report-25

Journal ref: Phys. Rev. D. 111 (2025) 074026

The Spectrum of C/2023 A3 Indicates A Depleted Composition

Authors: Yunyi Tang, Shihao Wang, Zixuan Lin, Xiaorui Yang, Xinyang Zhang, Songyu Jia, Sharon X. Wang

Abstract: We report a spectroscopic observation of comet C/2023 A3 using an 80 mm apochromatic (apo) refractor equipped with a custom-built spectrometer with a resolution of R~2,500 on the night of 4 October 2024. Sodium D lines were detected prominently, while no other emission lines, particularly carbon-bearing species, were observed, which suggests that comet C/2023 A3 may be carbon-depleted. The mobilit… ▽ More We report a spectroscopic observation of comet C/2023 A3 using an 80 mm apochromatic (apo) refractor equipped with a custom-built spectrometer with a resolution of R~2,500 on the night of 4 October 2024. Sodium D lines were detected prominently, while no other emission lines, particularly carbon-bearing species, were observed, which suggests that comet C/2023 A3 may be carbon-depleted. The mobility and flexibility of our observational setup highlight the value of amateur telescopes in observing low-altitude targets like C/2023 A3 as a complement to professional facilities. △ Less

Submitted 13 January, 2025; originally announced January 2025.

Comments: Published on RNAAS, Oct 2024. 4 pages, 1 figure. Further work in progress and comments are welcome

Journal ref: Res. Notes AAS 8 269 (2024)

An efficient unsupervised classification model for galaxy morphology: Voting clustering based on coding from ConvNeXt large model

Authors: Guanwen Fang, Yao Dai, Zesen Lin, Chichun Zhou, Jie Song, Yizhou Gu, Xiaotong Guo, Anqi Mao, Xu Kong

Abstract: In this work, we update the unsupervised machine learning (UML) step by proposing an algorithm based on ConvNeXt large model coding to improve the efficiency of unlabeled galaxy morphology classifications. The method can be summarized into three key aspects as follows: (1) a convolutional autoencoder is used for image denoising and reconstruction and the rotational invariance of the model is impro… ▽ More In this work, we update the unsupervised machine learning (UML) step by proposing an algorithm based on ConvNeXt large model coding to improve the efficiency of unlabeled galaxy morphology classifications. The method can be summarized into three key aspects as follows: (1) a convolutional autoencoder is used for image denoising and reconstruction and the rotational invariance of the model is improved by polar coordinate extension; (2) utilizing a pre-trained convolutional neural network (CNN) named ConvNeXt for encoding the image data. The features were further compressed via a principal component analysis (PCA) dimensionality reduction; (3) adopting a bagging-based multi-model voting classification algorithm to enhance robustness. We applied this model to I-band images of a galaxy sample with $I_{\rm mag}< 25$ in the COSMOS field. Compared to the original unsupervised method, the number of clustering groups required by the new method is reduced from 100 to 20. Finally, we managed to classify about 53\% galaxies, significantly improving the classification efficiency. To verify the validity of the morphological classification, we selected massive galaxies with $M(*)>10^{10}(M(sun))$ for morphological parameter tests. The corresponding rules between the classification results and the physical properties of galaxies on multiple parameter surfaces are consistent with the existing evolution model. Our method has demonstrated the feasibility of using large model encoding to classify galaxy morphology, which not only improves the efficiency of galaxy morphology classification, but also saves time and manpower. Furthermore, in comparison to the original UML model, the enhanced classification performance is more evident in qualitative analysis and has successfully surpassed a greater number of parameter tests. △ Less

Submitted 31 December, 2024; originally announced January 2025.

Comments: Accepted by A&A; 12 pages, 12 figures

Minute-cadence observations on Galactic plane with Wide Field Survey Telescope (WFST): Overview, methodology and early results

Authors: Jie Lin, Tinggui Wang, Minxuan Cai, Zhen Wan, Xuzhi Li, Lulu Fan, Qingfeng Zhu, Ji-an Jiang, Ning Jiang, Xu Kong, Zheyu Lin, Jiazheng Zhu, Zhengyan Liu, Jie Gao, Bin Li, Feng Li, Ming Liang, Hao Liu, Wei Liu, Wentao Luo, Jinlong Tang, Hairen Wang, Jian Wang, Yongquan Xue, Dazhi Yao , et al. (4 additional authors not shown)

Abstract: As the time-domain survey telescope of the highest survey power in the northern hemisphere currently, Wide Field Survey Telescope (WFST) is scheduled to hourly/daily/semi-weekly scan northern sky up to ~23 mag in four optical (ugri) bands. Unlike the observation cadences in the forthcoming regular survey missions, WFST performed "staring" observations toward Galactic plane in a cadence of… ▽ More As the time-domain survey telescope of the highest survey power in the northern hemisphere currently, Wide Field Survey Telescope (WFST) is scheduled to hourly/daily/semi-weekly scan northern sky up to ~23 mag in four optical (ugri) bands. Unlike the observation cadences in the forthcoming regular survey missions, WFST performed "staring" observations toward Galactic plane in a cadence of $\approx$1 minute for a total on-source time of about 13 hours, during the commissioning and pilot observation phases. Such an observation cadence is well applied in producing densely sampling light curves and hunting for stars exhibiting fast stellar variabilities. Here we introduce the primary methodologies in detecting variability, periodicity, and stellar flares among a half million sources from the minute-cadence observations, and present the WFST g-/r-band light curves generated from periodic variable stars and flaring stars. Benefit from high photometric precisions and deep detection limits of WFST, the observations have captured several rare variable stars, such as a variable hot white dwarf (WD) and an ellipsoidal WD binary candidate. By surveying the almost unexplored parameter spaces for variables, WFST will lead to new opportunities in discovering unique variable stars in the northern sky. △ Less

Submitted 16 March, 2025; v1 submitted 17 December, 2024; originally announced December 2024.

Comments: 20 pages, 12 figures, accepted by ApJS

Two Earth-size Planets and an Earth-size Candidate Transiting the Nearby Star HD 101581

Authors: Michelle Kunimoto, Zifan Lin, Sarah Millholland, Alexander Venner, Natalie R. Hinkel, Avi Shporer, Andrew Vanderburg, Jeremy Bailey, Rafael Brahm, Jennifer A. Burt, R. Paul Butler, Brad Carter, David R. Ciardi, Karen A. Collins, Kevin I. Collins, Knicole D. Colon, Jeffrey D. Crane, Tansu Daylan, Matías R. Díaz, John P. Doty, Fabo Feng, Eike W. Guenther, Jonathan Horner, Steve B. Howell, Jan Janik , et al. (21 additional authors not shown)

Abstract: We report the validation of multiple planets transiting the nearby ($d = 12.8$ pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481). The system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b ($R_{p} = 0.956_{-0.061}^{+0.063}~R_{\oplus}$, $P = 4.47$ days) and HD 101581 c ($R_{p} = 0.990_{-0.070}^{+0.070}~R_{\oplus}$,… ▽ More We report the validation of multiple planets transiting the nearby ($d = 12.8$ pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481). The system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b ($R_{p} = 0.956_{-0.061}^{+0.063}~R_{\oplus}$, $P = 4.47$ days) and HD 101581 c ($R_{p} = 0.990_{-0.070}^{+0.070}~R_{\oplus}$, $P = 6.21$ days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up. We also identify a signal that probably originates from a third transiting planet, TOI-6276.03 ($R_{p} = 0.982_{-0.098}^{+0.114}~R_{\oplus}$, $P = 7.87$ days). These planets are remarkably uniform in size and their orbits are evenly spaced, representing a prime example of the "peas-in-a-pod" architecture seen in other compact multi-planet systems. At $V = 7.77$, HD 101581 is the brightest star known to host multiple transiting planets smaller than $1.5~R_{\oplus}$. HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets. △ Less

Submitted 11 December, 2024; originally announced December 2024.

Comments: 25 pages, 13 figures. Accepted for publication in AJ

Interior and Gravity Field Models for Uranus Suggest Mixed-composition Interior: Implications for the Uranus Orbiter and Probe

Authors: Zifan Lin, Sara Seager, Benjamin P. Weiss

Abstract: The interior composition and structure of Uranus are ambiguous. It is unclear whether Uranus is composed of fully differentiated layers dominated by an icy mantle or has smooth compositional gradients. The Uranus Orbiter and Probe (UOP), the next NASA Flagship mission prioritized by the Planetary Science and Astrobiology Survey 2023-2032, will constrain the planet's interior by measuring its gravi… ▽ More The interior composition and structure of Uranus are ambiguous. It is unclear whether Uranus is composed of fully differentiated layers dominated by an icy mantle or has smooth compositional gradients. The Uranus Orbiter and Probe (UOP), the next NASA Flagship mission prioritized by the Planetary Science and Astrobiology Survey 2023-2032, will constrain the planet's interior by measuring its gravity and magnetic fields. To characterize the Uranian interior, here we present CORGI, a newly developed planetary interior and gravity model. We confirm that high degrees of mixing are required for Uranus interior models to be consistent with the $J_2$ and $J_4$ gravity harmonics measured by Voyager 2. Empirical models, which have smooth density profiles that require extensive mixing, can reproduce the Voyager 2 measurements. Distinct-layer models with mantles composed of H$_2$O-H/He or H$_2$O-CH$_4$-NH$_3$ mixtures are consistent with the Voyager 2 measurements if the heavy element mass fraction, $Z$, in the mantle $\lesssim85\%$, or if atmospheric $Z$ $\gtrsim25\%$. Our gravity harmonics model shows that UOP $J_2$ and $J_4$ measurements can distinguish between high ($Z\geq25\%$) and low ($Z=12.5\%$) atmospheric metallicity scenarios. The UOP can robustly constrain $J_6$ and potentially $J_8$ given polar orbits within rings. An ice-rich composition can naturally explain the source of Uranus' magnetic field. However, because the physical properties of rock-ice mixtures are poorly known, magnetic field generation by a rock-rich composition cannot be ruled out. Future experiments and simulations on realistic planetary building materials will be essential for refining Uranus interior models. △ Less

Submitted 8 December, 2024; originally announced December 2024.

Comments: 27 pages, 10 figures, 1 table, accepted for publication in the Planetary Science Journal

JWST-TST DREAMS: A Precise Water Abundance for Hot Jupiter WASP-17b from the NIRISS SOSS Transmission Spectrum

Authors: Dana R. Louie, Elijah Mullens, Lili Alderson, Ana Glidden, Nikole K. Lewis, Hannah R. Wakeford, Natasha E. Batalha, Knicole D. Colón, Amélie Gressier, Douglas Long, Michael Radica, Néstor Espinoza, Jayesh Goyal, Ryan J. MacDonald, Erin M. May, Sara Seager, Kevin B. Stevenson, Jeff A. Valenti, Natalie H. Allen, Caleb I. Cañas, Ryan C. Challener, David Grant, Jingcheng Huang, Zifan Lin, Daniel Valentine , et al. (5 additional authors not shown)

Abstract: Water has proven to be ubiquitously detected in near-infrared (NIR) transmission spectroscopy observations of hot Jupiter atmospheres, including WASP-17b. However, previous analyses of WASP-17b's atmosphere based upon Hubble Space Telescope (HST) and Spitzer data could not constrain the water abundance, finding that sub-solar, super-solar and bimodal posterior distributions were all statistically… ▽ More Water has proven to be ubiquitously detected in near-infrared (NIR) transmission spectroscopy observations of hot Jupiter atmospheres, including WASP-17b. However, previous analyses of WASP-17b's atmosphere based upon Hubble Space Telescope (HST) and Spitzer data could not constrain the water abundance, finding that sub-solar, super-solar and bimodal posterior distributions were all statistically valid. In this work, we observe one transit of the hot Jupiter WASP-17b using JWST's Near Infrared Imager and Slitless Spectrograph Single Object Slitless Spectroscopy (NIRISS SOSS) mode. We analyze our data using three independent data analysis pipelines, finding excellent agreement between results. Our transmission spectrum shows multiple H$_2$O absorption features and a flatter slope towards the optical than seen in previous HST observations. We analyze our spectrum using both PICASO+Virga forward models and free retrievals. POSEIDON retrievals provide a well-constrained super-solar $\log$(H$_2$O) abundance (-2.96$^{+0.31}_{-0.24}$), breaking the degeneracy from the previous HST/Spitzer analysis. We verify our POSEIDON results with petitRADTRANS retrievals. Additionally, we constrain the abundance of $\log$(H$^-$), -10.19$^{+0.30}_{-0.23}$, finding that our model including H$^-$ is preferred over our model without H$^-$ to 5.1 $σ$. Furthermore, we constrain the $\log$(K) abundance (-8.07$^{+0.58}_{-0.52}$) in WASP-17b's atmosphere for the first time using space-based observations. Our abundance constraints demonstrate the power of NIRISS SOSS's increased resolution, precision, and wavelength range to improve upon previous NIR space-based results. This work is part of a series of studies by our JWST Telescope Scientist Team (JWST-TST), in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). △ Less

Submitted 9 January, 2025; v1 submitted 4 December, 2024; originally announced December 2024.

Comments: Accepted for Publication in the Astronomical Journal (AJ) on 19 November 2024; 37 Pages, 17 Figures, 7 Tables. This version adds 2 co-authors, updates affiliations/acknowledgements, and corrects minor typos. Zenodo link to data is at https://zenodo.org/records/14193061

Early Grain Growth in the Young Protostellar Disk HH 212 Supported by Dust Self-Scattering Modeling

Authors: Ying-Chi Hu, Chin-Fei Lee, Zhe-Yu Daniel Lin, Zhi-Yun Li, John J. Tobin, Shih-Ping Lai

Abstract: Grain growth in disks around young stars plays a crucial role in the formation of planets. Early grain growth has been suggested in the HH 212 protostellar disk by previous polarization observations. To confirm it and to determine the grain size, we analyze high-resolution multi-band observations of the disk obtained with Atacama Large Millimeter/submillimeter Array (ALMA) in Bands 9 (0.4 mm), 7 (… ▽ More Grain growth in disks around young stars plays a crucial role in the formation of planets. Early grain growth has been suggested in the HH 212 protostellar disk by previous polarization observations. To confirm it and to determine the grain size, we analyze high-resolution multi-band observations of the disk obtained with Atacama Large Millimeter/submillimeter Array (ALMA) in Bands 9 (0.4 mm), 7 (0.9 mm), 6 (1.3 mm), 3 (3 mm) as well as with Very Large Array (VLA) in Band Ka (9 mm) and present new VLA data in Bands Q (7 mm), K (1.3 cm), and X (3 cm). We adopt a parameterized flared disk model to fit the continuum maps of the disk in these bands and derive the opacities, albedos, and opacity spectral index $\mathrmβ$ of the dust in the disk, taking into account the dust scattering ignored in the previous work modeling the multi-band data of this source. For the VLA bands, we only include the Band Q data in our modeling to avoid free-free emission contamination. The obtained opacities, albedos, and opacity spectral index $β$ (with a value of $\sim$ 1.2) suggest that the upper limit of maximum grain size in the disk be $\sim$ 130 $μ$m, consistent with that implied in the previous polarization observations in Band 7, supporting the grain growth in this disk. The values of the absorption opacities further highlight the need for a new dust composition model for Class 0/I disks. △ Less

Submitted 11 January, 2025; v1 submitted 29 November, 2024; originally announced December 2024.

Comments: 16 pages, 10 figures

Planets Around Solar Twins/Analogs (PASTA) I.: High precision stellar chemical abundance for 17 planet-hosting stars and the condensation temperature trend

Authors: Qinghui Sun, Sharon Xuesong Wang, Tianjun Gan, Chenyang Ji, Zitao Lin, Yuan-Sen Ting, Johanna Teske, Haining Li, Fan Liu, Xinyan Hua, Jiaxin Tang, Jie Yu, Jiayue Zhang, Mariona Badenas-Agusti, Andrew Vanderburg, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Jon M. Jenkins, Richard P. Schwarz, Tristan Guillot, Thiam-Guan Tan, Dennis M. Conti, Kevin I. Collins , et al. (8 additional authors not shown)

Abstract: The Sun is depleted in refractory elements compared to nearby solar twins, which may be linked to the formation of giant or terrestrial planets. Here we present high-resolution, high signal-to-noise spectroscopic data for 17 solar-like stars hosting planets, obtained with Magellan II/MIKE, to investigate whether this depletion is related to planet formation. We derive stellar parameters, including… ▽ More The Sun is depleted in refractory elements compared to nearby solar twins, which may be linked to the formation of giant or terrestrial planets. Here we present high-resolution, high signal-to-noise spectroscopic data for 17 solar-like stars hosting planets, obtained with Magellan II/MIKE, to investigate whether this depletion is related to planet formation. We derive stellar parameters, including stellar atmosphere, age, radius, mass, and chemical abundances for 22 elements from carbon to europium through line-by-line differential analysis. Our uncertainties range from 0.01 dex for Fe and Si to 0.08 dex for Sr, Y, and Eu. By comparing the solar abundances to those of the 17 stars, we investigate the differential abundance ([X/Fe]$_{\rm solar}$ - [X/Fe]$_{\rm star}$) versus condensation temperature ($T_c$) trend. In particular, we apply Galactic chemical evolution corrections to five solar twins within the full sample. Our results conform to previous studies that the Sun is relatively depleted in refractory compared to volatile elements. For both five solar twins and the rest of solar-like stars, we find that all stars hosting known gas giant planets exhibit negative $T_c$ trend slopes, suggesting that the Sun is relatively depleted in refractory elements compared to similar giant-planet-host stars. Additionally, we find no correlation between $T_c$ trend slopes and the total mass of detected terrestrial planets in each system, suggesting that terrestrial planet formation may not be the cause of refractory element depletion in the Sun. △ Less

Submitted 23 December, 2024; v1 submitted 20 November, 2024; originally announced November 2024.

Comments: 26 pages, 10 figures, 7 tables; accepted for publication in ApJ