Showing 1–50 of 235 results for author: Misra, K

Photometric and late-time spectropolarimetric observations of GRB 250129A afterglow

Authors: A. Ghosh, S. Razzaque, J. Barnard, J. C. Joshi, R. Gupta, D. A. H. Buckley, B. van Soelen, N. Dukiya, A. Gupta, A. S. Moskvitin, J. Cooper, S. Chandra, K. M. Jayasurya, K. Misra, N. Rawat, L. Resmi, O. I. Spiridonova, R. I. Uklein

Abstract: Gamma-Ray Burst (GRB) afterglows arise from the interaction of relativistic ejecta with the circumburst medium and are observed across the electromagnetic spectrum. Afterglow polarisation is expected at early and late phases depending on the presence of reverse shocks (RS) and the observer's viewing geometry relative to the jet. Polarimetric observations of GRB afterglows provide a unique diagnost… ▽ More Gamma-Ray Burst (GRB) afterglows arise from the interaction of relativistic ejecta with the circumburst medium and are observed across the electromagnetic spectrum. Afterglow polarisation is expected at early and late phases depending on the presence of reverse shocks (RS) and the observer's viewing geometry relative to the jet. Polarimetric observations of GRB afterglows provide a unique diagnostic tool to probe the geometry and structure of magnetic fields in the emitting region, which cannot be inferred from photometric or spectroscopic data alone. We report late-time (~19 hours post-burst) spectropolarimetric observations of GRB 250129A using the Southern African Large Telescope (SALT). The data reveal a hint of linear polarisation, with no evidence for rotation in the polarisation angle across wavelengths. Polarisation is typically expected during the early afterglow (<100 s) when the RS dominates. However, multi-wavelength modelling shows no indication of RS contribution at late times. Modelling incorporating both forward shock (FS) and RS components confirms that the RS fades rapidly after ~100 s. The afterglow emission is best explained by an off-axis viewing geometry of a jet with a Gaussian core and wings evolving in a uniform density environment. GRB 250129A thus provides rare observational evidence linking late-time polarisation to jet geometry and structure. △ Less

Submitted 24 March, 2026; originally announced March 2026.

Comments: 14 pages, 10 figures

Nebular Phase Evolution of SN 2023ixf (I): From Circumstellar Infrared Echo to the onset of in-situ Dust Formation in a Type II Supernova

Authors: Avinash Singh, S. Goto, A. Sarangi, J. Johansson, C. Fransson, S. Barmentloo, J. Sollerman, R. S. Teja, K. Maeda, T. Hamada, N. Sarin, M. Yamanaka, T. Nakaoka, K. S. Kawabata, S. Schulze, A. Jerkstrand, S. Rose, D. K. Sahu, A. Gangopadhyay, G. C. Anupama, T. Ahumada, S. Anand, A. Bochenek, S. J. Brennan, X. Chen , et al. (37 additional authors not shown)

Abstract: We present optical and near-infrared (NIR) photometric and spectroscopic observations of the Type II supernova SN 2023ixf spanning 150 to 750 days, combined with published early-time optical and infrared photometry, and JWST NIRSpec and MIRI spectroscopy, to disentangle circumstellar echo emission from newly formed internal dust. The combined dataset reveals an early infrared excess by 1.8 days, a… ▽ More We present optical and near-infrared (NIR) photometric and spectroscopic observations of the Type II supernova SN 2023ixf spanning 150 to 750 days, combined with published early-time optical and infrared photometry, and JWST NIRSpec and MIRI spectroscopy, to disentangle circumstellar echo emission from newly formed internal dust. The combined dataset reveals an early infrared excess by 1.8 days, a broad secondary NIR rebrightening over about 89 to 175 days, progressive attenuation of the red wing of H-alpha from about 132 days, and CO emission detected by about 217 days. We identify the onset of H-alpha asymmetry as the first direct signature for internal dust formation, and modeling of the H-alpha profile over 140 to 418 days yields an internal silicate-equivalent dust mass of about 1.5e-6 to 6e-5 solar masses. By contrast, the early infrared evolution is best interpreted as echo-dominated: the 1.8 to 33.6 day excess is consistent with a radiative-flash infrared echo from pre-existing circumstellar dust, while the 89 to 175 day rebrightening is more naturally explained by a more extended echo arising from structured wind material. JWST spectral energy distribution modeling further reveals a multi-component infrared continuum in which a cold graphite component traces lingering echo emission, while a colder silicate-bearing component grows to about 2e-3 solar masses, providing the strongest late-time spectral energy distribution evidence that internal CDS/ejecta dust becomes substantial. SN 2023ixf therefore provides one of the clearest time-resolved case studies of dust signatures in a Type II supernova, linking early circumstellar reprocessing with increasingly important in situ dust formation. △ Less

Submitted 14 March, 2026; originally announced March 2026.

Comments: 63 Pages, 26 Figures, 7 Tables, Submitted to AAS Journals, Comments are welcome!

Cross-Modal Taxonomic Generalization in (Vision-) Language Models

Authors: Tianyang Xu, Marcelo Sandoval-Castaneda, Karen Livescu, Greg Shakhnarovich, Kanishka Misra

Abstract: What is the interplay between semantic representations learned by language models (LM) from surface form alone to those learned from more grounded evidence? We study this question for a scenario where part of the input comes from a different modality -- in our case, in a vision-language model (VLM), where a pretrained LM is aligned with a pretrained image encoder. As a case study, we focus on the… ▽ More What is the interplay between semantic representations learned by language models (LM) from surface form alone to those learned from more grounded evidence? We study this question for a scenario where part of the input comes from a different modality -- in our case, in a vision-language model (VLM), where a pretrained LM is aligned with a pretrained image encoder. As a case study, we focus on the task of predicting hypernyms of objects represented in images. We do so in a VLM setup where the image encoder and LM are kept frozen, and only the intermediate mappings are learned. We progressively deprive the VLM of explicit evidence for hypernyms, and test whether knowledge of hypernyms is recoverable from the LM. We find that the LMs we study can recover this knowledge and generalize even in the most extreme version of this experiment (when the model receives no evidence of a hypernym during training). Additional experiments suggest that this cross-modal taxonomic generalization persists under counterfactual image-label mappings only when the counterfactual data have high visual similarity within each category. Taken together, these findings suggest that cross-modal generalization in LMs arises as a result of both coherence in the extralinguistic input and knowledge derived from language cues. △ Less

Submitted 8 March, 2026; originally announced March 2026.

An Afterglow Study of the "New Year's Burst" GRB 220101A

Authors: Agniva Roychowdhury, Tuomas Kangas, Andrew Fruchter, A. Pe'er, K. Bhirombhakdi, J. Graham, K. Misra, A. J. Levan, B. Cenko, A. Cucchiara, V. Cunningham, B. P. Gompertz, D. Perley, J. Racusin, N. R. Tanvir

Abstract: We present a detailed broadband afterglow study of GRB 220101A ($10^4\lesssimΔT\lesssim10^7$ s) combining multi-wavelength data from soft X-rays until 6 GHz. The afterglow light curves in both X-ray and optical show distinct steepening around $\sim9$ days, followed by a sharp post-break decay index of $\sim2.99\pm0.10$. We fit the light curves using the afterglow modelling package \texttt{afterglo… ▽ More We present a detailed broadband afterglow study of GRB 220101A ($10^4\lesssimΔT\lesssim10^7$ s) combining multi-wavelength data from soft X-rays until 6 GHz. The afterglow light curves in both X-ray and optical show distinct steepening around $\sim9$ days, followed by a sharp post-break decay index of $\sim2.99\pm0.10$. We fit the light curves using the afterglow modelling package \texttt{afterglowpy} for both Top-hat and Gaussian jets for different values of the electronic participation fraction $ξ$ from 0.01 to 1.0 and find that, although the radio behavior is well described by the $ξ=1.0$ case, the required circumburst medium (CBM) densities are very low, $<10^{-4}$ cm$^{-3}$. However, the resulting energy requirements are modest, $\sim10^{52}$ erg, with an electron energy distribution (EED) index $p\sim2.05$. Similar results are also obtained from an analytic model fit to the light curve, except the predicted $p$ is higher, $\sim2.40$. The observed post-break decay index of $2.99$ is at least 5$σ$ away from $p$, which is one of the steepest observed so far. We also find that when ignoring the radio observations, the CBM density is raised by a few orders of magnitude to $\sim0.01$ cm$^{-3}$ for $ξ=1.0$, still far from the expected ISM density ($>1$ cm$^{-3}$) of GRB environments, which are highly star forming regions. Similarly low ISM densities have been seen in modeling of other LAT GRBs as well, especially ones with reverse-shock features (e.g., GRBs 130427A, 160509A and 160625B), thereby hinting at either an issue with the standard model or possible evacuated cavities where GRBs explode. △ Less

Submitted 4 February, 2026; originally announced February 2026.

Comments: 17 pages, 10 figures. Submitted to The Astrophysical Journal

Which course? Discourse! Teaching Discourse and Generation in the Era of LLMs

Authors: Junyi Jessy Li, Yang Janet Liu, Kanishka Misra, Valentina Pyatkin, William Sheffield

Abstract: The field of NLP has undergone vast, continuous transformations over the past few years, sparking debates going beyond discipline boundaries. This begs important questions in education: how do we design courses that bridge sub-disciplines in this shifting landscape? This paper explores this question from the angle of discourse processing, an area with rich linguistic insights and computational mod… ▽ More The field of NLP has undergone vast, continuous transformations over the past few years, sparking debates going beyond discipline boundaries. This begs important questions in education: how do we design courses that bridge sub-disciplines in this shifting landscape? This paper explores this question from the angle of discourse processing, an area with rich linguistic insights and computational models for the intentional, attentional, and coherence structure of language. Discourse is highly relevant for open-ended or long-form text generation, yet this connection is under-explored in existing undergraduate curricula. We present a new course, "Computational Discourse and Natural Language Generation". The course is collaboratively designed by a team with complementary expertise and was offered for the first time in Fall 2025 as an upper-level undergraduate course, cross-listed between Linguistics and Computer Science. Our philosophy is to deeply integrate the theoretical and empirical aspects, and create an exploratory mindset inside the classroom and in the assignments. This paper describes the course in detail and concludes with takeaways from an independent survey as well as our vision for future directions. △ Less

Submitted 9 February, 2026; v1 submitted 2 February, 2026; originally announced February 2026.

Comments: accepted to the TeachNLP 2026 workshop (co-located with EACL 2026), camera-ready, 14 pages; aclpubcheck fixed and ref updated

SN 2023zcu: A Type IIP SN with Early Flash Features

Authors: Monalisa Dubey, Kuntal Misra, Géza Csörnyei, Raya Dastidar, D. Andrew Howell, David J. Sand, Stefano Valenti, WeiKang Zheng, Alexei V. Filippenko, Saurabh Jha, Jesper Sollerman, Peter Brown, Kate D. Alexander, Moira Andrews, Jennifer Andrews, Dre Betz, Emma Born, Kate Bostow, K. Azalee Bostroem, Sea'n J. Brennan, Thomas G. Brink, Collin Christy, Elma Chuang, Yize Dong, Naveen Dukiya , et al. (29 additional authors not shown)

Abstract: We present a detailed photometric and spectroscopic analysis of the Type IIP supernova SN~2023zcu, which exploded in the galaxy NGC~2139 (redshift $z$ = 0.006). SN~2023zcu exhibits a well-sampled light curve covering the rise, plateau, and nebular phases. It has an optically thick phase of $100.6 \pm 0.6$ d with a magnitude drop of $\sim$1.7 mag in the {\em V} band during the transition between th… ▽ More We present a detailed photometric and spectroscopic analysis of the Type IIP supernova SN~2023zcu, which exploded in the galaxy NGC~2139 (redshift $z$ = 0.006). SN~2023zcu exhibits a well-sampled light curve covering the rise, plateau, and nebular phases. It has an optically thick phase of $100.6 \pm 0.6$ d with a magnitude drop of $\sim$1.7 mag in the {\em V} band during the transition between the plateau and the nebular phases. Weak emission features in the early-time spectra indicate a low-level interaction between circumstellar material (CSM) and the SN ejecta. The spectral evolution is well sampled and exhibits a prominent P-Cygni profile of H$α$, a defining characteristic of Type IIP SNe. Signatures of metal-line formation (e.g., \ion{Fe}{2}, \ion{Ca}{2} near-infrared triplet) are also evident in the spectra as the SN evolves. Spectral modeling with the radiative-transfer code \texttt{TARDIS} during the early photospheric phase (8.7--35.5 d since explosion) yields photospheric temperatures decreasing from $\sim$9,000 to $\sim$6,000 K and expansion velocities declining from $\sim$10,000 to $\sim$5,400 km s$^{-1}$. A tailored expanding photosphere method (EPM) fit based on the \texttt{TARDIS} models provides a distance estimate of $27.8 \pm 2.0$ Mpc. Nebular-phase spectra and bolometric light-curve modeling suggest a progenitor mass in the range 12--15 M$_\odot$. This thorough analysis helps to constrain progenitor properties and explosion parameters, thereby strengthening our understanding of Type IIP SNe. △ Less

Submitted 21 January, 2026; originally announced January 2026.

Comments: 24 pages, 17 figures, 7 tables, accepted for publication in ApJ

Bears, all bears, and some bears. Language Constraints on Language Models' Inductive Inferences

Authors: Sriram Padmanabhan, Siyuan Song, Kanishka Misra

Abstract: Language places subtle constraints on how we make inductive inferences. Developmental evidence by Gelman et al. (2002) has shown children (4 years and older) to differentiate among generic statements ("Bears are daxable"), universally quantified NPs ("all bears are daxable") and indefinite plural NPs ("some bears are daxable") in extending novel properties to a specific member (all > generics > so… ▽ More Language places subtle constraints on how we make inductive inferences. Developmental evidence by Gelman et al. (2002) has shown children (4 years and older) to differentiate among generic statements ("Bears are daxable"), universally quantified NPs ("all bears are daxable") and indefinite plural NPs ("some bears are daxable") in extending novel properties to a specific member (all > generics > some), suggesting that they represent these types of propositions differently. We test if these subtle differences arise in general purpose statistical learners like Vision Language Models, by replicating the original experiment. On tasking them through a series of precondition tests (robust identification of categories in images and sensitivities to all and some), followed by the original experiment, we find behavioral alignment between models and humans. Post-hoc analyses on their representations revealed that these differences are organized based on inductive constraints and not surface-form differences. △ Less

Submitted 25 January, 2026; v1 submitted 14 January, 2026; originally announced January 2026.

A Study of Two Type IIb Supernovae: SNe 2008aq and 2019gaf

Authors: Mridweeka Singh, Devendra K. Sahu, Raya Dastidar, Rishabh Singh Teja, Anjasha Gangopadhyay, G. C. Anupama, D. Andrew Howell, K. Azalee Bostroem, Curtis McCully, Jamison Burke, Arti Joshi, Daichi Hiramatsu, Hyobin Im, Shubham Srivastav, Kuntal Misra

Abstract: We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN~2008aq showed prominent H $α$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN~2019gaf sho… ▽ More We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN~2008aq showed prominent H $α$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN~2019gaf shows shallow H$α$ absorption and He lines with almost similar strength. Both the SNe show transition from hydrogen-dominated spectra to helium-dominated spectra within a month after maximum brightness. The velocity evolution of SN~2008aq matches well with those of other well-studied Type IIb SNe, while SN~2019gaf shows higher velocities. Close to maximum light, the H $α$ and He I line velocities of SN~2019gaf are $\sim$ 2000 km sec$^{-1}$ and $\sim$ 4000 km sec$^{-1}$ higher than other well-studied Type IIb SNe. Semi-analytical modeling indicates SN~2019gaf to be a more energetic explosion with a smaller ejecta mass than SN~2008aq. The zero-age main-sequence (ZAMS) mass of the progenitor estimated using the nebular spectra of SN~2008aq ranges between 13 to 20 M$_\odot$, while for SN~2019gaf, the inferred ZAMS mass is between 13 to 25 M$_\odot$. The [O I] to [Ca II] lines flux ratio favors a less massive progenitor star in a binary system for both the SNe. △ Less

Submitted 12 January, 2026; originally announced January 2026.

Comments: 14 pages, 16 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

Abundance Stratification in Type Iax SN 2020rea with TARDIS

Authors: Sohini Kayal, P. Gayatri, Mridweeka Singh, Kuntal Misra

Abstract: Using the 1D Monte Carlo-based radiative transfer code TARDIS, we investigate the spectral evolution of the Type Iax supernova (SN) 2020rea from -7 days before to +21 days after maximum light. Our best-fit models indicate stratified, velocity-dependent abundances at early times, successfully reproducing most observed spectral features. As the SN evolves, the ejecta transition from a layered to a m… ▽ More Using the 1D Monte Carlo-based radiative transfer code TARDIS, we investigate the spectral evolution of the Type Iax supernova (SN) 2020rea from -7 days before to +21 days after maximum light. Our best-fit models indicate stratified, velocity-dependent abundances at early times, successfully reproducing most observed spectral features. As the SN evolves, the ejecta transition from a layered to a more homogeneous composition, posing an alternative to pure deflagration models that predict fully mixed ejecta. These results highlight the need for further investigation, as current pure deflagration models cannot fully explain the origin or spectral properties of Type Iax SNe like SN 2020rea. △ Less

Submitted 26 March, 2026; v1 submitted 30 December, 2025; originally announced December 2025.

Comments: 10 pages, 4 figures, accepted for publication in Journal of Astrophysics and Astronomy

Journal ref: Kayal, S., Gayatri, P., Singh, M. et al. Abundance stratification in type Iax SN 2020rea with TARDIS. J Astrophys Astron 47, 19 (2026)

GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic GRB from a Massive-Star Progenitor

Authors: Vishwajeet Swain, Varun Bhalerao, Harsh Kumar, Mehul Goyal, Ankur Ghosh, Utkarsh Pathak, Poonam Chandra, Tomas Ahumada, G. C. Anupama, Suman Bala, Sudhanshu Barway, Joshua S. Bloom, Dimple Dimple, Viraj R. Karambelkar, Mansi M. Kasliwal, Kuntal Misra, Josiah Purdum, Divita Saraogi, Jesper Sollerman, Aswin Suresh, Stefan J. van der Walt, Gaurav Waratkar

Abstract: We present a comprehensive multi-wavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission $E_{\mathrm{iso}} \sim 2.2 \times 10^{54}\ \mathrm{erg}$, released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow ($m_r = 15.55$) that faded rapidly… ▽ More We present a comprehensive multi-wavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission $E_{\mathrm{iso}} \sim 2.2 \times 10^{54}\ \mathrm{erg}$, released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow ($m_r = 15.55$) that faded rapidly ($\propto t^{-1.82}$). The prompt emission shows strong thermal photospheric emission, along with a non-thermal high-energy component. We explore the evolution of these components and find them to be consistent with theoretical expectations. Afterglow modeling reveals an energetic jet $E_{tot} \gtrsim 10^{52}\ \mathrm{erg}$ expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to understand the complete picture of GRB progenitors. △ Less

Submitted 2 March, 2026; v1 submitted 2 December, 2025; originally announced December 2025.

What do gravitational-wave observations tell us about Luminous Red Novae?

Authors: Dhruv Jain, Shasvath J. Kapadia, Kuntal Misra, Dimple, L. Resmi, Ajay Kumar Singh, K. G. Arun

Abstract: Luminous Red Novae (LRNe) have been argued to be related to the ejection of common envelopes (CEs) in binary star systems. Ejection of CEs leads to tightened stellar orbits capable of forming compact binaries that merge in Hubble time. As these mergers are seen by gravitational-wave (GW) detectors such as LIGO, Virgo and KAGRA (LVK), we ask what the merger rates of compact binaries in LVK tell us… ▽ More Luminous Red Novae (LRNe) have been argued to be related to the ejection of common envelopes (CEs) in binary star systems. Ejection of CEs leads to tightened stellar orbits capable of forming compact binaries that merge in Hubble time. As these mergers are seen by gravitational-wave (GW) detectors such as LIGO, Virgo and KAGRA (LVK), we ask what the merger rates of compact binaries in LVK tell us about the fraction of LRNe that lead to the formation of compact binaries that merge in Hubble time. Using the observed volumetric rates of LRNe from the Zwicky Transient Facility (ZTF) and of compact binary mergers from LVK observations, we derive limits on the fraction of LRNe that produce compact binaries that merge in Hubble time. Assuming the LRNe rate closely follows the star formation rate at any redshift, we use the delay time distribution models for compact binaries to compute the compact binary merger rate. A comparison of this merger rate with the latest volumetric rates of compact binary mergers from the fourth GW transient catalog (GWTC-4) at the present epoch of LVK allows us to constrain the above fraction. We find that only a fraction as small as $\sim 10^{-3}$ (median) of the LRNe correspond to the GW-observed binary neutron star (BNS) and neutron star-black hole (NSBH) mergers. This potentially implies that the majority of the LRNe population will not lead to mergers of compact objects, but other end products, such as stellar mergers. △ Less

Submitted 24 November, 2025; originally announced November 2025.

Comments: 7 Pages, 3 figures, 1 Table; To be Submitted in ApJL

Hey, wait a minute: on at-issue sensitivity in Language Models

Authors: Sanghee J. Kim, Kanishka Misra

Abstract: Evaluating the naturalness of dialogue in language models (LMs) is not trivial: notions of 'naturalness' vary, and scalable quantitative metrics remain limited. This study leverages the linguistic notion of 'at-issueness' to assess dialogue naturalness and introduces a new method: Divide, Generate, Recombine, and Compare (DGRC). DGRC (i) divides a dialogue as a prompt, (ii) generates continuations… ▽ More Evaluating the naturalness of dialogue in language models (LMs) is not trivial: notions of 'naturalness' vary, and scalable quantitative metrics remain limited. This study leverages the linguistic notion of 'at-issueness' to assess dialogue naturalness and introduces a new method: Divide, Generate, Recombine, and Compare (DGRC). DGRC (i) divides a dialogue as a prompt, (ii) generates continuations for subparts using LMs, (iii) recombines the dialogue and continuations, and (iv) compares the likelihoods of the recombined sequences. This approach mitigates bias in linguistic analyses of LMs and enables systematic testing of discourse-sensitive behavior. Applying DGRC, we find that LMs prefer to continue dialogue on at-issue content, with this effect enhanced in instruct-tuned models. They also reduce their at-issue preference when relevant cues (e.g., "Hey, wait a minute") are present. Although instruct-tuning does not further amplify this modulation, the pattern reflects a hallmark of successful dialogue dynamics. △ Less

Submitted 4 November, 2025; v1 submitted 14 October, 2025; originally announced October 2025.

Comments: 10 pages, 5 figures, 3 tables. See https://github.com/sangheek16/hey-wait-a-minute for code and data

WUGNECTIVES: Novel Entity Inferences of Language Models from Discourse Connectives

Authors: Daniel Brubaker, William Sheffield, Junyi Jessy Li, Kanishka Misra

Abstract: The role of world knowledge has been particularly crucial to predict the discourse connective that marks the discourse relation between two arguments, with language models (LMs) being generally successful at this task. We flip this premise in our work, and instead study the inverse problem of understanding whether discourse connectives can inform LMs about the world. To this end, we present WUGNEC… ▽ More The role of world knowledge has been particularly crucial to predict the discourse connective that marks the discourse relation between two arguments, with language models (LMs) being generally successful at this task. We flip this premise in our work, and instead study the inverse problem of understanding whether discourse connectives can inform LMs about the world. To this end, we present WUGNECTIVES, a dataset of 8,880 stimuli that evaluates LMs' inferences about novel entities in contexts where connectives link the entities to particular attributes. On investigating 17 different LMs at various scales, and training regimens, we found that tuning an LM to show reasoning behavior yields noteworthy improvements on most connectives. At the same time, there was a large variation in LMs' overall performance across connective type, with all models systematically struggling on connectives that express a concessive meaning. Our findings pave the way for more nuanced investigations into the functional role of language cues as captured by LMs. We release WUGNECTIVES at https://github.com/kanishkamisra/wugnectives △ Less

Submitted 1 February, 2026; v1 submitted 10 October, 2025; originally announced October 2025.

Comments: 19 pages total, 10 pages main; 8 figures total, 5 figures main; 10 tables total, 4 tables main

SN 2021tsz: A luminous, short photospheric phase Type II supernova in a low-metallicity host

Authors: R. Dastidar, G. Pignata, N. Dukiya, K. Misra, D. A. Howell, M. Singh, C. P. Gutiérrez, C. Pellegrino, A. Kumar, B. Ayala, A. Gangopadhyay, M. Newsome, E. Padilla Gonzalez, K. A. Bostroem, D. Hiramatsu, G. Terreran, C. McCully

Abstract: We present the analysis of the luminous Type II Supernova (SN) 2021tsz, which exploded in a low-luminosity galaxy. It reached a peak magnitude of -18.88 $\pm$ 0.13 mag in the $r$ band and exhibited an initial rapid decline of 4.05 $\pm$ 0.14 mag (100 d)$^{-1}$ from peak luminosity till $\sim$30 d. The photospheric phase is short, with the SN displaying bluer colours and a weak H$α$ absorption comp… ▽ More We present the analysis of the luminous Type II Supernova (SN) 2021tsz, which exploded in a low-luminosity galaxy. It reached a peak magnitude of -18.88 $\pm$ 0.13 mag in the $r$ band and exhibited an initial rapid decline of 4.05 $\pm$ 0.14 mag (100 d)$^{-1}$ from peak luminosity till $\sim$30 d. The photospheric phase is short, with the SN displaying bluer colours and a weak H$α$ absorption component--features consistent with other luminous, short-photospheric phase Type II SNe. A distinct transition from the photospheric to the radioactive tail phase in the $V$ band--as is common in hydrogen-rich Type II SNe--is not visible in SN 2021tsz, although a modest $\sim$1 mag drop is apparent in the redder filters. Hydrodynamic modelling suggests the luminosity is powered by ejecta-circumstellar material (CSM) interaction during the early phases (<30 days). Interaction with 0.6 M$_\odot$ of dense CSM extending to 3100 R$_\odot$ reproduces the observed luminosity, with an explosion energy of 1.3$\times$10$^{51}$ erg. The modelling indicates a pre-SN mass of 9 M$_\odot$, which includes a hydrogen envelope of 4 M$_\odot$, and a radius of $\sim$1000 R$_\odot$. Spectral energy distribution analysis and strong-line diagnostics reveal that the host galaxy of SN 2021tsz is a low-metallicity, dwarf galaxy. The low-metallicity environment and the derived high mass loss from the hydrodynamical modelling strongly support a binary progenitor system for SN 2021tsz. △ Less

Submitted 6 October, 2025; originally announced October 2025.

Comments: 17 pages, 12 figures, accepted for publication in A&A

Journal ref: A&A 703, A224 (2025)

SN 2024aecx: a fast-evolving Type IIb supernova with a prominent shock-cooling peak

Authors: Qiang Xi, Ning-Chen Sun, David Aguado, Ismael P'erez-Fournon, Fr'ed'erick Poidevin, Junjie Jin, Yiming Mao, Zexi Niu, Beichuan Wang, Yu Zhang, Kuntal Misra, Divyanshu Janghel, Justyn R. Maund, Amit Kumar, Samaporn Tinyanont, Liang-Duan Liu, Yu-Hao Zhang, Bhavya Ailawadhi, Monalisa Dubey, Zhen Guo, Anshika Gupta, Min He, Dhruv Jain, Debalina Kar, Wenxiong Li , et al. (14 additional authors not shown)

Abstract: SN 2024aecx is a nearby ($\sim$11 Mpc) Type IIb SN discovered within $\sim$1 d after explosion. In this paper we report high-cadence photometric (typically 0.5$\sim$1 day) and spectroscopic follow-up observations, conducted from as early as 0.27 d post discovery out to the nebular phase at 158.4 d. We analyze the environment of SN 2024aecx and derive a new distance (11.3$\pm$1.1 Mpc), metallicity… ▽ More SN 2024aecx is a nearby ($\sim$11 Mpc) Type IIb SN discovered within $\sim$1 d after explosion. In this paper we report high-cadence photometric (typically 0.5$\sim$1 day) and spectroscopic follow-up observations, conducted from as early as 0.27 d post discovery out to the nebular phase at 158.4 d. We analyze the environment of SN 2024aecx and derive a new distance (11.3$\pm$1.1 Mpc), metallicity and host extinction. The light curve exhibits a hot and luminous shock-cooling peak at the first few days, followed by a main peak with very rapid post-maximum decline. The earliest spectra are blue and featureless, while from 2.3 d after discovery prominent P-Cygni profiles emerge. At nebular phase, the emission lines exhibit asymmetric and double-peaked profiles, indicating asphericity and/or early dust formation in the ejecta. Nebular spectral modelling indicates a blueshifted O-rich clump moving toward observer, and the $[\text{OI}]/[\text{CaII}]$ line ratio suggests an intermediate-mass progenitor. We simulated the progenitor and explosion using a two-component model of shock cooling and radioactive $^{56}$Ni heating; our model favors an extended, low-mass H-rich envelope with $M_{\mathrm{e}} = 0.04\pm{0.01} M_{\odot}$ and a low ejecta mass of$M_{\mathrm{ej}} = 1.55^{+0.18}_{-0.14} M_{\odot}$. And the nebular-phase spectra and light-curve modelling both suggest that it most likely originated from an intermediate-mass binary progenitor system. The comprehensive monitoring of SN 2024aecx, coupled with the detailed characterization of its local environment, establishes it as a benchmark event for probing the progenitors and explosion mechanisms of Type IIb SNe. △ Less

Submitted 17 December, 2025; v1 submitted 15 September, 2025; originally announced September 2025.

Comments: 23 pages, 14 figures, Accepted for publication in ApJ

Vision-and-Language Training Helps Deploy Taxonomic Knowledge but Does Not Fundamentally Alter It

Authors: Yulu Qin, Dheeraj Varghese, Adam Dahlgren Lindström, Lucia Donatelli, Kanishka Misra, Najoung Kim

Abstract: Does vision-and-language (VL) training change the linguistic representations of language models in meaningful ways? Most results in the literature have shown inconsistent or marginal differences, both behaviorally and representationally. In this work, we start from the hypothesis that the domain in which VL training could have a significant effect is lexical-conceptual knowledge, in particular its… ▽ More Does vision-and-language (VL) training change the linguistic representations of language models in meaningful ways? Most results in the literature have shown inconsistent or marginal differences, both behaviorally and representationally. In this work, we start from the hypothesis that the domain in which VL training could have a significant effect is lexical-conceptual knowledge, in particular its taxonomic organization. Through comparing minimal pairs of text-only LMs and their VL-trained counterparts, we first show that the VL models often outperform their text-only counterparts on a text-only question-answering task that requires taxonomic understanding of concepts mentioned in the questions. Using an array of targeted behavioral and representational analyses, we show that the LMs and VLMs do not differ significantly in terms of their taxonomic knowledge itself, but they differ in how they represent questions that contain concepts in a taxonomic relation vs. a non-taxonomic relation. This implies that the taxonomic knowledge itself does not change substantially through additional VL training, but VL training does improve the deployment of this knowledge in the context of a specific task, even when the presentation of the task is purely linguistic. △ Less

Submitted 29 October, 2025; v1 submitted 17 July, 2025; originally announced July 2025.

Progenitor Insights of Type IIP SN 2018pq: A Comprehensive Photometric and Spectroscopic Study

Authors: Monalisa Dubey, Kuntal Misra, Raya Dastidar, Géza Csörnyei, Naveen Dukiya, Bhavya Ailawadhi, Iair Arcavi, K. Azalee Bostroem, Daichi Hiramatsu, Griffin Hossienzadeh, D. Andrew Howell, Curtis McCully, Ajay Kumar Singh

Abstract: We present high-cadence photometric and low-resolution (R $\sim$ 400--700) optical spectroscopic observations of Type IIP supernova, SN~2018pq, which exploded on the outskirts of the galaxy IC~3896A. The optically thick phase (``plateau'') lasts approximately 97 d, the plateau duration of normal Type IIP supernovae. SN~2018pq has a {\em V}-band absolute magnitude of $-16.42 \pm 0.01$ mag at 50 d,… ▽ More We present high-cadence photometric and low-resolution (R $\sim$ 400--700) optical spectroscopic observations of Type IIP supernova, SN~2018pq, which exploded on the outskirts of the galaxy IC~3896A. The optically thick phase (``plateau'') lasts approximately 97 d, the plateau duration of normal Type IIP supernovae. SN~2018pq has a {\em V}-band absolute magnitude of $-16.42 \pm 0.01$ mag at 50 d, resembles normal-luminous supernova, and the V-band decline rate of 0.42$\pm$0.06 mag 50 d$^{-1}$ during the plateau phase. A steeper decline rate of 11.87$\pm$1.68 mag 100 d$^{-1}$ was observed compared to that of typical Type IIP supernovae during the transition between plateau to nebular phase. We employ detailed radiative transfer spectra modelling, TARDIS, to reveal the photospheric temperature and velocity at two spectral epochs. The well-fitted model spectra indicate SN~2018pq is a spectroscopically normal Type IIP supernova. Semi-analytical light curve modelling suggests the progenitor as a red supergiant star with an ejecta mass of $\sim$11 $M_\odot$ and an initial radius of 424 $R_\odot$. On the contrary, hydrodynamical modelling suggests a higher mass progenitor between 14--16 $M_\odot$. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Comments: 12 pages, 14 figures, accepted for publication in MNRAS

SN 2023xgo: Helium-rich Type Icn or Carbon-Flash Type Ibn supernova?

Authors: Anjasha Gangopadhyay, Jesper Sollerman, Konstantinos Tsalapatas, Keiichi Maeda, Naveen Dukiya, Steve Schulze, Claes Fransson, Nikhil Sarin, Priscila J. Pessi, Mridweeka Singh, Jacob Wise, Tatsuya Nakaoka, Avinash Singh, Raya Dastidar, Miho Kawabata, Yu-Jing Qing, Kaustav K. Das, Daniel Perley, Christoffer Fremling, Kenta Taguchi, K-Ryan Hinds, Ragnhild Lunnan, Rishabh Singh Teja, Monalisa Dubey, Bhavya Ailawadhi , et al. (13 additional authors not shown)

Abstract: We present observations of SN~2023xgo, a transitional Type Ibn/Icn supernova, from $-5.6$ to $+63$~days relative to the $r$-band peak. Early spectra show C~III $λ5696$ emission reminiscent of Type~Icn SNe, which later gives way to Type~Ibn features. The He~I velocities ($1800$--$10{,}000$~km~s$^{-1}$) and pseudo-equivalent widths are among the highest in the Ibn/Icn class. The light curve declines… ▽ More We present observations of SN~2023xgo, a transitional Type Ibn/Icn supernova, from $-5.6$ to $+63$~days relative to the $r$-band peak. Early spectra show C~III $λ5696$ emission reminiscent of Type~Icn SNe, which later gives way to Type~Ibn features. The He~I velocities ($1800$--$10{,}000$~km~s$^{-1}$) and pseudo-equivalent widths are among the highest in the Ibn/Icn class. The light curve declines at $0.14$~mag~d$^{-1}$ until $+30$~days, consistent with SNe~Ibn/Icn and slower than fast transients. SN~2023xgo is the faintest in our SN~Ibn sample ($M_r=-17.65\pm0.04$) but shows typical color and host properties. Semi-analytical modeling of the light curve suggests a compact CSM shell ($\sim 10^{12}$--$10^{13}$~cm) and a mass-loss rate of $10^{-4}$--$10^{-3}$~$M_{\odot}$~yr$^{-1}$, with CSM and ejecta masses of $\sim 0.22$ and $0.12$~$M_{\odot}$, respectively. Post-maximum light-curve and spectral modeling favor a $\sim 3$~$M_{\odot}$ helium-star progenitor with extended ($\sim 10^{15}$~cm), stratified CSM (density exponent $n=2.9$) and a mass-loss rate of $0.1$--$2.7$~$M_{\odot}$~yr$^{-1}$. These two mass-loss regimes imply a radially varying CSM, shaped by asymmetry or temporal changes in the progenitor's mass loss. This behavior is compatible with both binary and single-star evolution. We argue that the early Icn-like features arise from hot carbon ionization and fade to Ibn-like signatures as the ejecta and CSM cool, making SN~2023xgo a rare probe of the connection between SNe~Icn, SNe~Ibn, and Ibn events with ejecta signatures. △ Less

Submitted 8 September, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: 24 figures and 6 table including appendix, Accepted for publication in MNRAS

semantic-features: A User-Friendly Tool for Studying Contextual Word Embeddings in Interpretable Semantic Spaces

Authors: Jwalanthi Ranganathan, Rohan Jha, Kanishka Misra, Kyle Mahowald

Abstract: We introduce semantic-features, an extensible, easy-to-use library based on Chronis et al. (2023) for studying contextualized word embeddings of LMs by projecting them into interpretable spaces. We apply this tool in an experiment where we measure the contextual effect of the choice of dative construction (prepositional or double object) on the semantic interpretation of utterances (Bresnan, 2007)… ▽ More We introduce semantic-features, an extensible, easy-to-use library based on Chronis et al. (2023) for studying contextualized word embeddings of LMs by projecting them into interpretable spaces. We apply this tool in an experiment where we measure the contextual effect of the choice of dative construction (prepositional or double object) on the semantic interpretation of utterances (Bresnan, 2007). Specifically, we test whether "London" in "I sent London the letter." is more likely to be interpreted as an animate referent (e.g., as the name of a person) than in "I sent the letter to London." To this end, we devise a dataset of 450 sentence pairs, one in each dative construction, with recipients being ambiguous with respect to person-hood vs. place-hood. By applying semantic-features, we show that the contextualized word embeddings of three masked language models show the expected sensitivities. This leaves us optimistic about the usefulness of our tool. △ Less

Submitted 6 June, 2025; originally announced June 2025.

Comments: SCiL 2025 Camera Ready Extended Abstract

Is It JUST Semantics? A Case Study of Discourse Particle Understanding in LLMs

Authors: William Sheffield, Kanishka Misra, Valentina Pyatkin, Ashwini Deo, Kyle Mahowald, Junyi Jessy Li

Abstract: Discourse particles are crucial elements that subtly shape the meaning of text. These words, often polyfunctional, give rise to nuanced and often quite disparate semantic/discourse effects, as exemplified by the diverse uses of the particle "just" (e.g., exclusive, temporal, emphatic). This work investigates the capacity of LLMs to distinguish the fine-grained senses of English "just", a well-stud… ▽ More Discourse particles are crucial elements that subtly shape the meaning of text. These words, often polyfunctional, give rise to nuanced and often quite disparate semantic/discourse effects, as exemplified by the diverse uses of the particle "just" (e.g., exclusive, temporal, emphatic). This work investigates the capacity of LLMs to distinguish the fine-grained senses of English "just", a well-studied example in formal semantics, using data meticulously created and labeled by expert linguists. Our findings reveal that while LLMs exhibit some ability to differentiate between broader categories, they struggle to fully capture more subtle nuances, highlighting a gap in their understanding of discourse particles. △ Less

Submitted 4 June, 2025; originally announced June 2025.

Comments: To be published in Findings of The 63rd Annual Meeting of the Association for Computational Linguistics (ACL 2025). The main paper is 5 pages and contains 3 figures and 1 table. In total, the paper is 12 pages and contains 8 figures and 5 tables (References + Appendix)

JWST and Ground-based Observations of the Type Iax Supernovae SN 2024pxl and SN 2024vjm: Evidence for Weak Deflagration Explosions

Authors: Lindsey A. Kwok, Mridweeka Singh, Saurabh W. Jha, Stéphane Blondin, Raya Dastidar, Conor Larison, Adam A. Miller, Jennifer E. Andrews, Moira Andrews, G. C. Anupama, Katie Auchettl, Dominik Bánhidi, Barnabas Barna, K. Azalee Bostroem, Thomas G. Brink, Régis Cartier, Ping Chen, Collin T. Christy, David A. Coulter, Sofia Covarrubias, Kyle W. Davis, Connor B. Dickinson, Yize Dong, Joseph R. Farah, Alexei V. Filippenko , et al. (67 additional authors not shown)

Abstract: We present panchromatic optical $+$ near-infrared (NIR) $+$ mid-infrared (MIR) observations of the intermediate-luminosity Type Iax supernova (SN Iax) 2024pxl and the extremely low-luminosity SN Iax 2024vjm. JWST observations provide unprecedented MIR spectroscopy of SN Iax, spanning from $+$11 to $+$42 days past maximum light. We detect forbidden emission lines in the MIR at these early times whi… ▽ More We present panchromatic optical $+$ near-infrared (NIR) $+$ mid-infrared (MIR) observations of the intermediate-luminosity Type Iax supernova (SN Iax) 2024pxl and the extremely low-luminosity SN Iax 2024vjm. JWST observations provide unprecedented MIR spectroscopy of SN Iax, spanning from $+$11 to $+$42 days past maximum light. We detect forbidden emission lines in the MIR at these early times while the optical and NIR are dominated by permitted lines with an absorption component. Panchromatic spectra at early times can thus simultaneously show nebular and photospheric lines, probing both inner and outer layers of the ejecta. We identify spectral lines not seen before in SN Iax, including [Mg II] 4.76 $μ$m, [Mg II] 9.71 $μ$m, [Ne II] 12.81 $μ$m, and isolated O I 2.76 $μ$m that traces unburned material. Forbidden emission lines of all species are centrally peaked with similar kinematic distributions, indicating that the ejecta are well mixed in both SN 2024pxl and SN 2024vjm, a hallmark of pure deflagration explosion models. Radiative transfer modeling of SN 2024pxl shows good agreement with a weak deflagration of a near-Chandrasekhar-mass white dwarf, but additional IR flux is needed to match the observations, potentially attributable to a surviving remnant. Similarly, we find SN 2024vjm is also best explained by a weak deflagration model, despite the large difference in luminosity between the two supernovae. Future modeling should push to even weaker explosions and include the contribution of a bound remnant. Our observations demonstrate the diagnostic power of panchromatic spectroscopy for unveiling explosion physics in thermonuclear supernovae. △ Less

Submitted 16 October, 2025; v1 submitted 5 May, 2025; originally announced May 2025.

Comments: 27 pages, 16 figures, 5 tables, published in ApJL

Journal ref: The Astrophysical Journal Letters, Volume 989, Issue 2, id.L33, 24 pp., August 2025

Photometry and Spectroscopy of SN 2024pxl: A Luminosity Link Among Type Iax Supernovae

Authors: Mridweeka Singh, Lindsey A. Kwok, Saurabh W. Jha, R. Dastidar, Conor Larison, Alexei V. Filippenko, Jennifer E. Andrews, Moira Andrews, G. C. Anupama, Prasiddha Arunachalam, Katie Auchettl, Dominik BÁnhidi, Barnabas Barna, K. Azalee Bostroem, Thomas G. Brink, RÉgis Cartier, Ping Chen, Collin T. Christy, David A. Coulter, Sofia Covarrubias, Kyle W. Davis, Connor B. Dickinson, Yize Dong, Joseph Farah, Andreas FlÖrs , et al. (68 additional authors not shown)

Abstract: We present extensive ultraviolet to optical photometric and optical to near-infrared (NIR) spectroscopic follow-up observations of the nearby intermediate-luminosity ($M_V = -16.81\pm0.19$~mag) Type Iax supernova (SN) 2024pxl in NGC 6384. SN~2024pxl exhibits a faster light curve than the high-luminosity members of this class, and slower than low-luminosity events. The observationally well-constrai… ▽ More We present extensive ultraviolet to optical photometric and optical to near-infrared (NIR) spectroscopic follow-up observations of the nearby intermediate-luminosity ($M_V = -16.81\pm0.19$~mag) Type Iax supernova (SN) 2024pxl in NGC 6384. SN~2024pxl exhibits a faster light curve than the high-luminosity members of this class, and slower than low-luminosity events. The observationally well-constrained rise time of $\sim$11 days and an estimated synthesized $^{56}$Ni mass of 0.03\, M$_\odot$, based on analytical modeling of the integrated spectral energy distribution light curve, are consistent with models of the weak deflagration of a carbon-oxygen white dwarf. Our optical spectral sequence of SN~2024pxl shows weak \ion{Si}{2} lines and spectral evolution similar to other high-luminosity Type Iax SNe, but also a prominent early-time \ion{C}{2} line, like lower-luminosity Type Iax SNe. The late-time optical spectrum of SN~2024pxl closely matches that of SN~2014dt, and its NIR spectral evolution aligns with that of other well-studied, high-luminosity Type Iax SNe. The spectral-line expansion velocities of SN~2024pxl are at the lower end of the Type Iax SN velocity distribution, and the velocity distribution of iron-group elements compared to intermediate-mass elements suggests that the ejecta are mixed on large scales, as expected in pure deflagration models. SN~2024pxl exhibits characteristics intermediate between those of high-luminosity and low-luminosity Type~Iax SNe, further establishing a link across this diverse class. △ Less

Submitted 3 February, 2026; v1 submitted 5 May, 2025; originally announced May 2025.

Comments: 22 figures, 9 tables, Accepted for publication in The Astrophysical Journal

Waymo Driverless Car Data Analysis and Driving Modeling using CNN and LSTM

Authors: Aashish Kumar Misraa, Naman Jain, Saurav Singh Dhakad

Abstract: Self driving cars has been the biggest innovation in the automotive industry, but to achieve human level accuracy or near human level accuracy is the biggest challenge that research scientists are facing today. Unlike humans autonomous vehicles do not work on instincts rather they make a decision based on the training data that has been fed to them using machine learning models using which they ca… ▽ More Self driving cars has been the biggest innovation in the automotive industry, but to achieve human level accuracy or near human level accuracy is the biggest challenge that research scientists are facing today. Unlike humans autonomous vehicles do not work on instincts rather they make a decision based on the training data that has been fed to them using machine learning models using which they can make decisions in different conditions they face in the real world. With the advancements in machine learning especially deep learning the self driving car research skyrocketed. In this project we have presented multiple ways to predict acceleration of the autonomous vehicle using Waymo's open dataset. Our main approach was to using CNN to mimic human action and LSTM to treat this as a time series problem. △ Less

Submitted 29 April, 2025; originally announced May 2025.

Comments: This work contributed to research acknowledged in https://doi.org/10.3390/app10062046

SN 2023vbg: A Type IIn Supernova Resembling SN 2009ip, with a Long-Duration Precursor and Early-Time Bump

Authors: Sota Goto, Masayuki Yamanaka, Takahiro Nagayama, Keiichi Maeda, Miho Kawabata, D. K. Sahu, Avinash Singh, Anjasha Gangopadhyay, Naveen Dkuniya, Kuntal Misra, Monalisa Dubey, Bhavya Ailawadhi

Abstract: Type IIn supernovae (SNe) resembling SN 2009ip (09ip-like SNe) originate from the interaction between circumstellar material (CSM) and the ejecta. This subclass not only shares similar observational properties around the maximum, but is commonly characterized by a long-duration precursor before its maximum. Investigating the observed properties of the precursor provides constraints on the mass-los… ▽ More Type IIn supernovae (SNe) resembling SN 2009ip (09ip-like SNe) originate from the interaction between circumstellar material (CSM) and the ejecta. This subclass not only shares similar observational properties around the maximum, but is commonly characterized by a long-duration precursor before its maximum. Investigating the observed properties of the precursor provides constraints on the mass-loss history of the progenitor. We present observational data of SN 2023vbg, a 09ip-like type IIn SN that displayed unique observational properties compared to other 09ip-like SNe. SN 2023vbg showed a long-duration precursor at approximately Mg = -14 mag lasting for about 100 days, followed by a bright bump at Mg = -17 mag at 12-25 days before the maximum. The luminosity of the precursor is similar to those of other 09ip-like SNe, but the bright bump has not been observed in other cases. After reaching the peak luminosity, the light curve exhibited a relatively smooth decline. While the H-alpha profile displays two velocity components (approximately 500 and 3000 km/s), a broad component observed in other 09ip-like SNe was not seen, though it may emerge later. We suggest that these properties are explained by the difference in the CSM structure as compared to other 09ip-like SNe; SN 2023vbg had an inner denser CSM component, as well as generally smooth CSM density distribution on a more extended scale, than in the others. Such diversity of CSM likely reflects the diversity of pre-SN outbursts, which in turn may mirror the range of evolutionary pathways in the final stages of the progenitors. △ Less

Submitted 25 July, 2025; v1 submitted 22 April, 2025; originally announced April 2025.

Comments: 13 pages, 9 figures, accepted for publication in the ApJ (July 2025)

On Language Models' Sensitivity to Suspicious Coincidences

Authors: Sriram Padmanabhan, Kanishka Misra, Kyle Mahowald, Eunsol Choi

Abstract: Humans are sensitive to suspicious coincidences when generalizing inductively over data, as they make assumptions as to how the data was sampled. This results in smaller, more specific hypotheses being favored over more general ones. For instance, when provided the set {Austin, Dallas, Houston}, one is more likely to think that this is sampled from "Texas Cities" over "US Cities" even though both… ▽ More Humans are sensitive to suspicious coincidences when generalizing inductively over data, as they make assumptions as to how the data was sampled. This results in smaller, more specific hypotheses being favored over more general ones. For instance, when provided the set {Austin, Dallas, Houston}, one is more likely to think that this is sampled from "Texas Cities" over "US Cities" even though both are compatible. Suspicious coincidence is strongly connected to pragmatic reasoning, and can serve as a testbed to analyze systems on their sensitivity towards the communicative goals of the task (i.e., figuring out the true category underlying the data). In this paper, we analyze whether suspicious coincidence effects are reflected in language models' (LMs) behavior. We do so in the context of two domains: 1) the number game, where humans made judgments of whether a number (e.g., 4) fits a list of given numbers (e.g., 16, 32, 2); and 2) by extending the number game setup to prominent cities. For both domains, the data is compatible with multiple hypotheses and we study which hypothesis is most consistent with the models' behavior. On analyzing five models, we do not find strong evidence for suspicious coincidences in LMs' zero-shot behavior. However, when provided access to the hypotheses space via chain-of-thought or explicit prompting, LMs start to show an effect resembling suspicious coincidences, sometimes even showing effects consistent with humans. Our study suggests that inductive reasoning behavior in LMs can be enhanced with explicit access to the hypothesis landscape. △ Less

Submitted 12 April, 2025; originally announced April 2025.

Both Direct and Indirect Evidence Contribute to Dative Alternation Preferences in Language Models

Authors: Qing Yao, Kanishka Misra, Leonie Weissweiler, Kyle Mahowald

Abstract: Language models (LMs) tend to show human-like preferences on a number of syntactic phenomena, but the extent to which these are attributable to direct exposure to the phenomena or more general properties of language is unclear. We explore this with the English dative alternation (DO: "gave Y the X" vs. PO: "gave the X to Y"), using a controlled rearing paradigm wherein we iteratively train small L… ▽ More Language models (LMs) tend to show human-like preferences on a number of syntactic phenomena, but the extent to which these are attributable to direct exposure to the phenomena or more general properties of language is unclear. We explore this with the English dative alternation (DO: "gave Y the X" vs. PO: "gave the X to Y"), using a controlled rearing paradigm wherein we iteratively train small LMs on systematically manipulated input. We focus on two properties that affect the choice of alternant: length and animacy. Both properties are directly present in datives but also reflect more global tendencies for shorter elements to precede longer ones and animates to precede inanimates. First, by manipulating and ablating datives for these biases in the input, we show that direct evidence of length and animacy matters, but easy-first preferences persist even without such evidence. Then, using LMs trained on systematically perturbed datasets to manipulate global length effects (re-linearizing sentences globally while preserving dependency structure), we find that dative preferences can emerge from indirect evidence. We conclude that LMs' emergent syntactic preferences come from a mix of direct and indirect sources. △ Less

Submitted 9 August, 2025; v1 submitted 26 March, 2025; originally announced March 2025.

Superior monogamy and polygamy relations and estimates of concurrence

Authors: Yue Cao, Naihuan Jing, Kailash Misra, Yiling Wang

Abstract: It is well known that any well-defined bipartite entanglement measure $\mathcal{E}$ obeys $γ$th-monogamy relations Eq. (1.1) and assisted measure $\mathcal{E}_{a}$ obeys $δ$th-polygamy relations Eq. (1.2). Recently, we presented a class of tighter parameterized monogamy relation for the $α$th $(α\geqγ)$ power based on Eq. (1.1). This study provides a family of tighter lower (resp. upper) bounds of… ▽ More It is well known that any well-defined bipartite entanglement measure $\mathcal{E}$ obeys $γ$th-monogamy relations Eq. (1.1) and assisted measure $\mathcal{E}_{a}$ obeys $δ$th-polygamy relations Eq. (1.2). Recently, we presented a class of tighter parameterized monogamy relation for the $α$th $(α\geqγ)$ power based on Eq. (1.1). This study provides a family of tighter lower (resp. upper) bounds of the monogamy (resp. polygamy) relations in a unified manner. In the first part of the paper, the following three basic problems are focused: (i) tighter monogamy relation for the $α$th ($0\leq α\leq γ$) power of any bipartite entanglement measure $\mathcal{E}$ based on Eq. (1.1); (ii) tighter polygamy relation for the $β$th ($ β\geq δ$) power of any bipartite assisted entanglement measure $\mathcal{E}_{a}$ based on Eq. (1.2); (iii) tighter polygamy relation for the $ω$th ($0\leq ω\leq δ$) power of any bipartite assisted entanglement measure $\mathcal{E}_{a}$ based on Eq. (1.2). In the second part, using the tighter polygamy relation for the $ω$th ($0\leq ω\leq 2$) power of CoA, we obtain good estimates or bounds for the $ω$th ($0\leq ω\leq 2$) power of concurrence for any $N$-qubit pure states $|ψ\rangle_{AB_{1}\cdots B_{N-1}}$ under the partition $AB_{1}$ and $B_{2}\cdots B_{N-1}$. Detailed examples are given to illustrate that our findings exhibit greater strength across all the region. △ Less

Submitted 1 March, 2025; originally announced March 2025.

MSC Class: Primary: 81P68; Secondary: 81P40

Journal ref: Eur. Phys. J. Plus 140 (2025), 101 (14pp)

The 4m International Liquid Mirror Telescope: Construction, operation, and science

Authors: Jean Surdej, Paul Hickson, Kuntal Misra, Dipankar Banerjee, Bhavya Ailawadhi, Talat Akhunov, Ermanno Borra, Monalisa Dubey, Naveen Dukiya, Sara Filali, Joschua Hellemeier, Manisha Kharayat, Brajesh Kumar, Hitesh Kumar, Mukesh Kumar, T. S. Kumar, Priyanshi Kumari, Vibhore Negi, Anna Pospieszalska-Surdej, Sarath Prabhavu, Bikram Pradhan, Kumar Pranshu, Himanshu Rawat, B. Krishna Reddy, Arun Sasidharan Pillai , et al. (4 additional authors not shown)

Abstract: The International Liquid Mirror Telescope (ILMT) project was motivated by the need for an inexpensive 4 metre diameter optical telescope that could be devoted entirely to astronomical surveys. Its scientific programmes include the detection and study of transients, variable objects, asteroids, comets, space debris and low surface brightness galaxies. To this end, a collaboration was formed between… ▽ More The International Liquid Mirror Telescope (ILMT) project was motivated by the need for an inexpensive 4 metre diameter optical telescope that could be devoted entirely to astronomical surveys. Its scientific programmes include the detection and study of transients, variable objects, asteroids, comets, space debris and low surface brightness galaxies. To this end, a collaboration was formed between the Institute of Astrophysics and Geophysics (Liège University, Belgium), several Canadian universities (University of British Columbia, Laval University, University of Montreal, University of Toronto, York University, University of Victoria) and the Aryabhatta Research Institute of Observational Sciences (ARIES, India). After several years of design work in Belgium and construction in India on the ARIES Devasthal site, the telescope saw its first light on 29 April 2022. Its commissioning phase lasted from May 2022 until June 2023 (beginning of the monsoon). The ILMT was inaugurated on 21 March 2023 and has been in regular operation since October 2023. The telescope continuously observes the sky passing at the zenith using the SDSS g', r', and i' filters. This paper describes the ILMT, its operation, performance and shows some initial results. △ Less

Submitted 1 February, 2025; originally announced February 2025.

Comments: 12 pages, 18 figures, accepted for publication in Astronomy & Astrophysics

PyLMT: A transient detection pipeline for the 4-m International Liquid Mirror Telescope

Authors: Kumar Pranshu, Kuntal Misra, Bhavya Ailawadhi, Monalisa Dubey, Naveen Dukiya, Sara Filali, Paul Hickson, Brajesh Kumar, Vibhore Negi, Jean Surdej

Abstract: The International Liquid Mirror Telescope (ILMT) is a 4-m aperture, zenith-pointing telescope with a field-of-view of 22', situated in the foothills of the Himalayas. The telescope operates in continuous survey mode, making it a useful instrument for time-domain astronomy, particularly for detecting transients, variable stars, active galactic nuclei variability, and asteroids. This paper presents… ▽ More The International Liquid Mirror Telescope (ILMT) is a 4-m aperture, zenith-pointing telescope with a field-of-view of 22', situated in the foothills of the Himalayas. The telescope operates in continuous survey mode, making it a useful instrument for time-domain astronomy, particularly for detecting transients, variable stars, active galactic nuclei variability, and asteroids. This paper presents the PyLMT transient detection pipeline to detect such transient/varying sources in the ILMT images. The pipeline utilises the image subtraction technique to compare a pair of images from the same field, identifying such sources in subtracted images with the help of convolutional neural networks (CNN) based real/bogus classifiers. The test accuracies determined for the real/bogus classifiers ranged from 94% to 98%. The resulting precision of the pipeline calculated over candidate alerts in the ILMT frames is 0.91. It also houses a CNN-aided transient candidate classifier that classifies the transient/variable candidates based on host morphology. The test accuracy of the candidate classifier is 98.6%. It has the provision to identify catalogued asteroids and other solar system objects using public databases. The median execution time of the pipeline is approximately 29 minutes per image of 17 minutes exposure. Relevant CNNs have been trained on data acquired with the ILMT during the cycle of October-November 2022. Subsequent tests on those images have confirmed the detection of numerous catalogued asteroids, variable stars, and other uncatalogued sources. The pipeline has been operational and has detected 12 extragalactic transients, including 2 new discoveries in the November 2023-May 2024 observation cycle. △ Less

Submitted 1 February, 2025; originally announced February 2025.

Comments: 21 pages, 26 figures, accepted for publication in MNRAS

SN 2018is: a low-luminosity Type IIP supernova with narrow hydrogen emission lines at early phases

Authors: R. Dastidar, K. Misra, S. Valenti, D. J. Sand, A. Pastorello, A. Reguitti, G. Pignata, S. Benetti, S. Bose, A. Gangopadhyay, M. Singh, L. Tomasella, J. E. Andrews, I. Arcavi, C. Ashall, C. Bilinski, K. A. Bostroem, D. A. H. Buckley, G. Cannizzaro, L. Chomiuk, E. Congiu, S. Dong, Y. Dong, N. Elias-Rosa, M. Fraser , et al. (9 additional authors not shown)

Abstract: We present a comprehensive photometric and spectroscopic study of the Type IIP SN 2018is. The $V$-band luminosity and the expansion velocity at 50 days post-explosion are $-$15.1$\pm$0.2 mag (corrected for A$_V$=1.34 mag) and 1400 km s$^{-1}$, classifying it as a low-luminosity SN II. The recombination phase in the $V$-band is shorter, lasting around 110 days, and exhibits a steeper decline (1.0 m… ▽ More We present a comprehensive photometric and spectroscopic study of the Type IIP SN 2018is. The $V$-band luminosity and the expansion velocity at 50 days post-explosion are $-$15.1$\pm$0.2 mag (corrected for A$_V$=1.34 mag) and 1400 km s$^{-1}$, classifying it as a low-luminosity SN II. The recombination phase in the $V$-band is shorter, lasting around 110 days, and exhibits a steeper decline (1.0 mag per 100 days) compared to most other low-luminosity SNe II. Additionally, the optical and near-infrared spectra display hydrogen emission lines that are strikingly narrow, even for this class. The Fe II and Sc II line velocities are at the lower end of the typical range for low-luminosity SNe II. Semi-analytical modelling of the bolometric light curve suggests an ejecta mass of $\sim$8 M$_\odot$, corresponding to a pre-supernova mass of $\sim$9.5 M$_\odot$, and an explosion energy of $\sim$0.40 $\times$ 10$^{51}$ erg. Hydrodynamical modelling further indicates that the progenitor had a zero-age main sequence mass of 9 M$_\odot$, coupled with a low explosion energy of 0.19 $\times$ 10$^{51}$ erg. The nebular spectrum reveals weak [O I] $λλ$6300,6364 lines, consistent with a moderate-mass progenitor, while features typical of Fe core-collapse events, such as He I, [C I], and [Fe I], are indiscernible. However, the redder colours and low ratio of Ni to Fe abundance do not support an electron-capture scenario either. As a low-luminosity SN II with an atypically steep decline during the photospheric phase and remarkably narrow emission lines, SN 2018is contributes to the diversity observed within this population. △ Less

Submitted 2 January, 2025; originally announced January 2025.

Comments: 25 pages, 21 figures, accepted for publication in A&A

Journal ref: A&A 694, A260 (2025)

Use of Electron Paramagnetic resonance (EPR) technique to build quantum computers: n-qubit (n=1,2,3,4) Toffoli Gates

Authors: Sayan Manna, Sushil K. Misra

Abstract: It is shown theoretically how to use the EPR (Electron Paramagnetic Resonance) technique, using electron spins as qubits, coupled with each other by the exchange interaction, to set the configuration of n qubits (n=1,2,3,4) at resonance, in conjunction with pulses, to construct the NOT (one qubit), CNOT (two qubits), CCNOT (three qubits), CCCNOT (four qubits) Toffoli gates, which can be exploited… ▽ More It is shown theoretically how to use the EPR (Electron Paramagnetic Resonance) technique, using electron spins as qubits, coupled with each other by the exchange interaction, to set the configuration of n qubits (n=1,2,3,4) at resonance, in conjunction with pulses, to construct the NOT (one qubit), CNOT (two qubits), CCNOT (three qubits), CCCNOT (four qubits) Toffoli gates, which can be exploited to build a quantum computer. This is unique to EPR, wherein exchange-coupled electron spins are used. This is not possible with NMR (Nuclear Magnetic Resonance), that uses nuclear spins as qubits, which do not couple with each other by the exchange interaction. △ Less

Submitted 21 May, 2025; v1 submitted 13 November, 2024; originally announced November 2024.

Journal ref: Adv. Quantum Technol. 2025, e2500115 (2025)

AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system

Authors: L. Hernández-García, A. M. Muñoz-Arancibia, P. Lira, G. Bruni, J. Cuadra, P. Arévalo, P. Sánchez-Sáez, S. Bernal, F. E. Bauer, M. Catelan, F. Panessa, M. Pávez-Herrera, C. Ricci, I. Reyes-Jainaga, B. Ailawadhi, V. Chavushyan, R. Dastidar, A. Deconto-Machado, F. Förster, A. Gangopadhyay, A. García-Pérez, I. Márquez, J. Masegosa, K. Misra, V. M Patiño-Alvarez , et al. (3 additional authors not shown)

Abstract: With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT 2021hdr, whose optical light cur… ▽ More With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT 2021hdr, whose optical light curve used to be consistent with a classic Seyfert 1 nucleus, which was also confirmed by its optical spectrum and high-energy properties. From late 2021, AT 2021hdr started to present sudden brightening episodes in the form of oscillating peaks in the Zwicky Transient Facility (ZTF) alert stream, and the same shape is observed in X-rays and UV from Swift data. The oscillations occur every about 60-90 days with amplitudes of around 0.2 mag in the g and r bands. Very Long Baseline Array (VLBA) observations show no radio emission at milliarcseconds scale. It is argued that these findings are inconsistent with a standard tidal disruption event (TDE), a binary supermassive black hole (BSMBH), or a changing-look active galactic nucleus (AGN); neither does this object resemble previous observed AGN flares, and disk or jet instabilities are an unlikely scenario. Here, we propose that the behavior of AT 2021hdr might be due to the tidal disruption of a gas cloud by a BSMBH. In this scenario, we estimate that the putative binary has a separation of about 0.83 mpc and would merge in about 70000 years. This galaxy is located at 9 kpc from a companion galaxy, and in this work we report this merger for the first time. The oscillations are not related to the companion galaxy. △ Less

Submitted 13 November, 2024; originally announced November 2024.

Comments: 11 pages, 5 figures, 2 tables, plus appendices. Accepted for publication in Astronomy & Astrophysics. NASA press release available at https://science.nasa.gov/missions/swift/nasas-swift-studies-gas-churning-monster-black-holes/ doi: 10.1051/0004-6361/202451305

On the Game of Moksha-Patam

Authors: Aninda Kumar Nanda, Amit Kumar Misra

Abstract: The game of Moksha-Patam, often known as `Chutes and Ladders', is a widely played indoor game worldwide. While studies have been conducted regarding the nature of an individual board, the possibilities that open up when we change the positions of the chutes and the ladders on a board are mostly unventured. In this article, we classify and study the different possible types of Moksha-Patam Boards,… ▽ More The game of Moksha-Patam, often known as `Chutes and Ladders', is a widely played indoor game worldwide. While studies have been conducted regarding the nature of an individual board, the possibilities that open up when we change the positions of the chutes and the ladders on a board are mostly unventured. In this article, we classify and study the different possible types of Moksha-Patam Boards, introduce a naming convention for them and establish a count for the boards that can be constructed adhering to some basic assumptions of the game. △ Less

Submitted 5 November, 2024; originally announced November 2024.

Comments: 22 pages, 5 figures

MSC Class: 60J10; 60J20; 05A15

Characterizing the Role of Similarity in the Property Inferences of Language Models

Authors: Juan Diego Rodriguez, Aaron Mueller, Kanishka Misra

Abstract: Property inheritance -- a phenomenon where novel properties are projected from higher level categories (e.g., birds) to lower level ones (e.g., sparrows) -- provides a unique window into how humans organize and deploy conceptual knowledge. It is debated whether this ability arises due to explicitly stored taxonomic knowledge vs. simple computations of similarity between mental representations. How… ▽ More Property inheritance -- a phenomenon where novel properties are projected from higher level categories (e.g., birds) to lower level ones (e.g., sparrows) -- provides a unique window into how humans organize and deploy conceptual knowledge. It is debated whether this ability arises due to explicitly stored taxonomic knowledge vs. simple computations of similarity between mental representations. How are these mechanistic hypotheses manifested in contemporary language models? In this work, we investigate how LMs perform property inheritance with behavioral and causal representational analysis experiments. We find that taxonomy and categorical similarities are not mutually exclusive in LMs' property inheritance behavior. That is, LMs are more likely to project novel properties from one category to the other when they are taxonomically related and at the same time, highly similar. Our findings provide insight into the conceptual structure of language models and may suggest new psycholinguistic experiments for human subjects. △ Less

Submitted 9 March, 2025; v1 submitted 29 October, 2024; originally announced October 2024.

Comments: Published at NAACL 2025

SN 2021foa: the bridge between SN IIn and Ibn

Authors: Anjasha Gangopadhyay, Naveen Dukiya, Takashi J Moriya, Masaomi Tanaka, Keiichi Maeda, D. Andrew Howell, Mridweeka Singh, Avinash Singh, Jesper Sollerman, Koji S Kawabata, Sean J Brennan, Craig Pellegrino, Raya Dastidar, Tatsuya Nakaoka, Miho Kawabata, Kuntal Misra, Steve Schulze, Poonam Chandra, Kenta Taguchi, Devendra K Sahu, Curtis McCully, K. Azalee Bostroem, Estefania Padilla Gonzalez, Megan Newsome, Daichi Hiramatsu , et al. (4 additional authors not shown)

Abstract: We present the long-term photometric and spectroscopic analysis of a transitioning SN~IIn/Ibn from $-$10.8 d to 150.7 d post $V$-band maximum. SN~2021foa shows prominent He {\sc i} lines comparable in strength to the H$α$ line around peak, placing SN~2021foa between the SN~IIn and SN~Ibn populations. The spectral comparison shows that it resembles the SN~IIn population at pre-maximum, becomes inte… ▽ More We present the long-term photometric and spectroscopic analysis of a transitioning SN~IIn/Ibn from $-$10.8 d to 150.7 d post $V$-band maximum. SN~2021foa shows prominent He {\sc i} lines comparable in strength to the H$α$ line around peak, placing SN~2021foa between the SN~IIn and SN~Ibn populations. The spectral comparison shows that it resembles the SN~IIn population at pre-maximum, becomes intermediate between SNe~IIn/Ibn and at post-maximum matches with SN~IIn 1996al. The photometric evolution shows a precursor at $-$50 d and a light curve shoulder around 17d. The peak luminosity and color evolution of SN 2021foa are consistent with most SNe~IIn and Ibn in our comparison sample. SN~2021foa shows the unique case of a SN~IIn where the narrow P-Cygni in H$α$ becomes prominent at 7.2 days. The H$α$ profile consists of a narrow (500 -- 1200 km s$^{-1}$) component, intermediate width (3000 -- 8000 km s$^{-1}$) and broad component in absorption. Temporal evolution of the H$α$ profile favours a disk-like CSM geometry. Hydrodynamical modelling of the lightcurve well reproduces a two-component CSM structure with different densities ($ρ$ $\propto$ r$^{-2}$ -- $ρ$ $\propto$ r$^{-5}$), mass-loss rates (10$^{-3}$ -- 10$^{-1}$ M$_{\odot}$ yr$^{-1}$) assuming a wind velocity of 1000 km s$^{-1}$ and having a CSM mass of 0.18 M$_{\odot}$. The overall evolution indicates that SN~2021foa most likely originated from a LBV star transitioning to a WR star with the mass-loss rate increasing in the period from 5 to 0.5 years before the explosion or it could be due to a binary interaction. △ Less

Submitted 29 January, 2025; v1 submitted 4 September, 2024; originally announced September 2024.

Comments: Accepted for publication in MNRAS; 21 pages, 14 figures, 4 tables

A systematic framework for generating novel experimental hypotheses from language models

Authors: Kanishka Misra, Najoung Kim

Abstract: Neural language models (LMs) have been shown to capture complex linguistic patterns, yet their utility in understanding human language and more broadly, human cognition, remains debated. While existing work in this area often evaluates human-machine alignment, few studies attempt to translate findings from this enterprise into novel insights about humans. To this end, we propose a systematic frame… ▽ More Neural language models (LMs) have been shown to capture complex linguistic patterns, yet their utility in understanding human language and more broadly, human cognition, remains debated. While existing work in this area often evaluates human-machine alignment, few studies attempt to translate findings from this enterprise into novel insights about humans. To this end, we propose a systematic framework for hypothesis generation that uses LMs to simulate outcomes of experiments that do not yet exist in the literature. We instantiate this framework in the context of a specific research question in child language development: dative verb acquisition and cross-structural generalization. Through this instantiation, we derive novel, untested hypotheses: the alignment between argument ordering and discourse prominence features of exposure contexts modulates how children generalize new verbs to unobserved structures. Additionally, we also design a set of experiments that can test these hypotheses in the lab with children. This work contributes both a domain-general framework for systematic hypothesis generation via simulated learners and domain-specific, lab-testable hypotheses for child language acquisition research. △ Less

Submitted 9 April, 2026; v1 submitted 9 August, 2024; originally announced August 2024.

Comments: Revised version

CSS161010: a luminous, fast blue optical transient with broad blueshifted hydrogen lines

Authors: Claudia P. Gutiérrez, Seppo Mattila, Peter Lundqvist, Luc Dessart, Santiago González-Gaitán, Peter G. Jonker, Subo Dong, Deanne Coppejans, Ping Chen, Panos Charalampopoulos, Nancy Elias-Rosa, Thomas Reynolds, Christopher Kochanek, Morgan Fraser, Andrea Pastorello, Mariusz Gromadzki, Jack Neustadt, Stefano Benetti, Erkki Kankare, Tuomas Kangas, Rubina Kotak, Maximilian D. Stritzinger, Thomas Wevers, Bing Zhang, David Bersier , et al. (16 additional authors not shown)

Abstract: We present ultraviolet, optical and near-infrared photometric and optical spectroscopic observations of the luminous, fast blue optical transient (LFBOT), CSS161010:045834-081803 (CSS161010). The transient was found in a low-redshift (z=0.033) dwarf galaxy. The light curves of CSS161010 are characterized by an extremely fast evolution and blue colours. The V-band light curve shows that CSS161010 r… ▽ More We present ultraviolet, optical and near-infrared photometric and optical spectroscopic observations of the luminous, fast blue optical transient (LFBOT), CSS161010:045834-081803 (CSS161010). The transient was found in a low-redshift (z=0.033) dwarf galaxy. The light curves of CSS161010 are characterized by an extremely fast evolution and blue colours. The V-band light curve shows that CSS161010 reaches an absolute peak of M$_{V}^{max}=-20.66\pm0.06$ mag in 3.8 days from the start of the outburst. After maximum, CSS161010 follows a power-law decline $\propto t^{-2.8\pm0.1}$ in all optical bands. These photometric properties are comparable to those of well-observed LFBOTs such as AT 2018cow, AT 2020mrf and AT 2020xnd. However, unlike these objects, the spectra of CSS161010 show a remarkable transformation from a blue and featureless continuum to spectra dominated by very broad, entirely blueshifted hydrogen emission lines of velocities of up to 10% of the speed of light. The persistent blueshifted emission and the lack of any emission at the rest wavelength of CSS161010 are unique features not seen in any transient before CSS161010. The combined observational properties of CSS161010 and its M$_{*}\sim10^{8}$ M$_\odot$ dwarf galaxy host favour the tidal disruption of a star by an intermediate-mass black hole as its origin. △ Less

Submitted 22 October, 2024; v1 submitted 8 August, 2024; originally announced August 2024.

Comments: 29 pages (including the appendix); 8 figures in the main text, 4 figures and 8 tables in the appendix. Accepted for publication in ApJ

A study in scarlet -- II. Spectroscopic properties of a sample of Intermediate Luminosity Red Transients

Authors: G. Valerin, A. Pastorello, E. Mason, A. Reguitti, S. Benetti, Y. -Z. Cai, T. -W. Chen, D. Eappachen, N. Elias-Rosa, M. Fraser, A. Gangopadhyay, E. Y. Hsiao, D. A. Howell, C. Inserra, L. Izzo, J. Jencson, E. Kankare, R. Kotak, P. Lundqvist, P. A. Mazzali, K. Misra, G. Pignata, S. J. Prentice, D. J. Sand, S. J. Smartt , et al. (43 additional authors not shown)

Abstract: We investigate the spectroscopic characteristics of Intermediate Luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. We present the extensive optical and near-infrared (NIR) spectroscopic monitoring of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. First we focus on the evolution of… ▽ More We investigate the spectroscopic characteristics of Intermediate Luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. We present the extensive optical and near-infrared (NIR) spectroscopic monitoring of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. First we focus on the evolution of the most prominent spectral features observed in the low resolution spectra, then we discuss more in detail the high resolution spectrum collected for NGC 300 2008OT-1 with the Very Large Telescope equipped with UVES. Finally we analyse late time spectra of NGC 300 2008OT-1 and AT 2019ahd through comparisons with both synthetic and observed spectra. Balmer and Ca lines dominate the optical spectra, revealing the presence of slowly moving circumstellar medium (CSM) around the objects. The line luminosity of H$α$, H$β$ and Ca II NIR triplet presents a double peaked evolution with time, possibly indicative of interaction between fast ejecta and the slow CSM. The high resolution spectrum of NGC 300 2008OT-1 reveals a complex circumstellar environment, with the transient being surrounded by a slow ($\sim$30 km s$^{-1}$) progenitor wind. At late epochs, optical spectra of NGC 300 2008OT-1 and AT 2019ahd show broad ($\sim$2500 km s$^{-1}$) emission features at $\sim$6170 A and $\sim$7000 A which are unprecedented for ILRTs. We find that these lines originate most likely from the blending of several narrow lines, possibly of iron-peak elements. △ Less

Submitted 31 July, 2024; originally announced July 2024.

Comments: 28 pages, 19 figures. Submitted to A&A

Journal ref: A&A 695, A43 (2025)

A study in scarlet -- I. Photometric properties of a sample of Intermediate Luminosity Red Transients

Authors: G. Valerin, A. Pastorello, A. Reguitti, S. Benetti, Y. -Z. Cai, T. -W. Chen, D. Eappachen, N. Elias-Rosa, M. Fraser, A. Gangopadhyay, E. Y. Hsiao, D. A. Howell, C. Inserra, L. Izzo, J. Jencson, E. Kankare, R. Kotak, P. A. Mazzali, K. Misra, G. Pignata, S. J. Prentice, D. J. Sand, S. J. Smartt, M. D. Stritzinger, L. Tartaglia , et al. (35 additional authors not shown)

Abstract: We investigate the photometric characteristics of a sample of Intermediate Luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. We present the multi-wavelength photometric follow-up of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. Through the analysis and modelling of their spectral… ▽ More We investigate the photometric characteristics of a sample of Intermediate Luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. We present the multi-wavelength photometric follow-up of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. Through the analysis and modelling of their spectral energy distribution and bolometric light curves we infer the physical parameters associated with these transients. All four objects display a single peaked light curve which ends in a linear decline in magnitudes at late phases. A flux excess with respect to a single black body emission is detected in the infrared domain for three objects in our sample, a few months after maximum. This feature, commonly found in ILRTs, is interpreted as a sign of dust formation. Mid infrared monitoring of NGC 300 2008OT-1 761 days after maximum allows us to infer the presence of $\sim$10$^{-3}$-10$^{-5}$ M$_{\odot}$ of dust, depending on the chemical composition and the grain size adopted. The late time decline of the bolometric light curves of the considered ILRTs is shallower than expected for $^{56}$Ni decay, hence requiring an additional powering mechanism. James Webb Space Telescope observations of AT 2019abn prove that the object has faded below its progenitor luminosity in the mid-infrared domain, five years after its peak. Together with the disappearance of NGC 300 2008OT-1 in Spitzer images seven years after its discovery, this supports the terminal explosion scenario for ILRTs. With a simple semi-analytical model we try to reproduce the observed bolometric light curves in the context of few M$_{\odot}$ of material ejected at few 10$^{3}$ km s$^{-1}$ and enshrouded in an optically thick circumstellar medium. △ Less

Submitted 31 July, 2024; originally announced July 2024.

Comments: 21 pages, 15 figures plus 20 additional pages of data in appendix. Submitted to A&A

Journal ref: A&A 695, A42 (2025)

Rates and beaming angles of GRBs associated with compact binary coalescences

Authors: Shasvath J. Kapadia, Dimple, Dhruv Jain, Kuntal Misra, K. G. Arun, L. Resmi

Abstract: Some, if not all, binary neutron star (BNS) coalescences, and a fraction of neutron - star black hole (NSBH) mergers, are thought to produce sufficient mass-ejection to power Gamma-Ray Bursts (GRBs). However, this fraction, as well as the distribution of beaming angles of BNS-associated GRBs, are poorly constrained from observation. Recent work applied machine learning tools to analyze GRB light c… ▽ More Some, if not all, binary neutron star (BNS) coalescences, and a fraction of neutron - star black hole (NSBH) mergers, are thought to produce sufficient mass-ejection to power Gamma-Ray Bursts (GRBs). However, this fraction, as well as the distribution of beaming angles of BNS-associated GRBs, are poorly constrained from observation. Recent work applied machine learning tools to analyze GRB light curves observed by {\textit{Fermi}}/GBM and {\it Swift}/BAT. GRBs were segregated into multiple distinct clusters, with the tantalizing possibility that one of them (BNS cluster) could be associated with BNSs and another (NSBH cluster) with NSBHs. As a proof of principle, assuming that all GRBs detected by {\it Fermi}/GBM and {\it Swift}/BAT associated with BNSs (NSBHs) lie in the BNS (NSBH) cluster, we estimate their rates ($\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$). We compare these rates with corresponding BNS and NSBH rates estimated by the LIGO-Virgo-Kagra (LVK) collaboration from the first three observing runs (O1, O2, O3). We find that the BNS rates are consistent with LVK's rate estimates, assuming a uniform distribution of beaming fractions ($f_b \in [0.01, 0.1]$). Conversely, using the LVK's BNS rate estimates, assuming all BNS mergers produce GRBs, we are able to constrain the beaming angle distribution to $θ_j \in [0.8^{\circ}, 33.5^{\circ}]$ at $90\%$ confidence. We similarly place limits on the fraction of GRB-Bright NSBHs as $f_B \in [1.3\%, 63\%]$ ($f_B \in [0.4\%, 15\%]$) with {\it Fermi}/GBM ({\it Swift}/BAT) data. △ Less

Submitted 15 November, 2024; v1 submitted 26 July, 2024; originally announced July 2024.

Comments: 10 pages, 3 figures

Journal ref: ApJ Letters 976 L10 (2024)

Tighter parameterized monogamy relations

Authors: Yue Cao, Naihuan Jing, Kailash Misra, Yiling Wang

Abstract: We seek a systematic tightening method to represent the monogamy relation for some measure in multipartite quantum systems. By introducing a family of parametrized bounds, we obtain tighter lowering bounds for the monogamy relation compared with the most recently discovered relations. We provide detailed examples to illustrate why our bounds are better. We seek a systematic tightening method to represent the monogamy relation for some measure in multipartite quantum systems. By introducing a family of parametrized bounds, we obtain tighter lowering bounds for the monogamy relation compared with the most recently discovered relations. We provide detailed examples to illustrate why our bounds are better. △ Less

Submitted 25 July, 2024; originally announced July 2024.

Comments: 17pp

MSC Class: Primary: 85

Journal ref: Quantum Inf. Process. (2024) 23:282

HI and CO spectroscopy of the unusual host of GRB 171205A: A grand design spiral galaxy with a distorted HI field

Authors: A. de Ugarte Postigo, M. Michalowski, C. C. Thoene, S. Martin, A. Ashok, J. F. Agui Fernandez, M. Bremer, K. Misra, D. A. Perley, K. E. Heintz, S. V. Cherukuri, W. Dimitrov, T. Geron, A. Ghosh, L. Izzo, D. A. Kann, M. P. Koprowski, A. Lesniewska, J. K. Leung, A. Levan, A. Omar, D. Oszkiewicz, M. Polinska, L. Resmi, S. Schulze

Abstract: GRBs produced by the collapse of massive stars are usually found near the most prominent star-forming regions of star-forming galaxies. GRB 171205A happened in the outskirts of a spiral galaxy, a peculiar location in an atypical GRB host. In this paper we present a highly-resolved study of the molecular gas of this host, with CO(1-0) observations from ALMA. We compare with GMRT atomic HI observati… ▽ More GRBs produced by the collapse of massive stars are usually found near the most prominent star-forming regions of star-forming galaxies. GRB 171205A happened in the outskirts of a spiral galaxy, a peculiar location in an atypical GRB host. In this paper we present a highly-resolved study of the molecular gas of this host, with CO(1-0) observations from ALMA. We compare with GMRT atomic HI observations, and with data at other wavelengths to provide a broad-band view of the galaxy. The ALMA observations have a spatial resolution of 0.2" and a spectral resolution of 10 km/s, observed when the afterglow had a flux density of ~53 mJy. This allowed a molecular study both in emission and absorption. The HI observations allowed to study the host galaxy and its extended environment. The CO emission shows an undisturbed spiral structure with a central bar, and no significant emission at the location of the GRB. Our CO spectrum does not reveal any CO absorption, with a column density limit of < 10^15 cm^-2. This argues against the progenitor forming in a massive molecular cloud. The molecular gas traces the galaxy arms with higher concentration in the regions dominated by dust. The HI gas does not follow the stellar light or the molecular gas and is concentrated in two blobs, with no emission towards the centre of the galaxy, and is slightly displaced towards the southwest of the galaxy, where the GRB exploded. Within the extended neighbourhood of the host galaxy, we identify another prominent HI source at the same redshift, at a projected distance of 188 kpc. Our observations show that the progenitor of this GRB is not associated to a massive molecular cloud, but more likely related to low-metallicity atomic gas. The distortion in the HI gas field is indicator of an odd environment that could have triggered star formation and could be linked to a past interaction with the companion galaxy. △ Less

Submitted 25 June, 2024; v1 submitted 24 June, 2024; originally announced June 2024.

Comments: 13 pages, 10 figures, 8 tables, A&A submitted after 1st referee review

Status of Astronomy Education in India: A Baseline Survey

Authors: Moupiya Maji, Surhud More, Aniket Sule, Vishaak Balasubramanya, Ankit Bhandari, Hum Chand, Kshitij Chavan, Avik Dasgupta, Anindya De, Jayant Gangopadhyay, Mamta Gulati, Priya Hasan, Syed Ishtiyaq, Meraj Madani, Kuntal Misra, Amoghavarsha N, Divya Oberoi, Subhendu Pattnaik, Mayuri Patwardhan, Niruj Mohan Ramanujam, Pritesh Ranadive, Disha Sawant, Paryag Sharma, Twinkle Sharma, Sai Shetye , et al. (6 additional authors not shown)

Abstract: We present the results of a nation-wide baseline survey, conducted by us, for the status of Astronomy education among secondary school students in India. The survey was administered in 10 different languages to over 2000 students from diverse backgrounds, and it explored multiple facets of their perspectives on astronomy. The topics included students' views on the incorporation of astronomy in cur… ▽ More We present the results of a nation-wide baseline survey, conducted by us, for the status of Astronomy education among secondary school students in India. The survey was administered in 10 different languages to over 2000 students from diverse backgrounds, and it explored multiple facets of their perspectives on astronomy. The topics included students' views on the incorporation of astronomy in curricula, their grasp of fundamental astronomical concepts, access to educational resources, cultural connections to astronomy, and their levels of interest and aspirations in the subject. We find notable deficiencies in students' knowledge of basic astronomical principles, with only a minority demonstrating proficiency in key areas such as celestial sizes, distances, and lunar phases. Furthermore, access to resources such as telescopes and planetariums remain limited across the country. Despite these challenges, a significant majority of students expressed a keen interest in astronomy. We further analyze the data along socioeconomic and gender lines. Particularly striking were the socioeconomic disparities, with students from resource-poor backgrounds often having lower levels of access and proficiency. Some differences were observed between genders, although not very pronounced. The insights gleaned from this study hold valuable implications for the development of a more robust astronomy curriculum and the design of effective teacher training programs in the future. △ Less

Submitted 18 June, 2024; originally announced June 2024.

Comments: 15 pages, 19 figures

Diversity in Fermi/GBM Gamma Ray Bursts: New insights from Machine Learning

Authors: Dimple, K. Misra, K. G. Arun

Abstract: Classification of gamma-ray bursts (GRBs) has been a long-standing puzzle in high-energy astrophysics. Recent observations challenge the traditional short vs. long viewpoint, where long GRBs are thought to originate from the collapse of massive stars and short GRBs from compact binary mergers. Machine learning (ML) algorithms have been instrumental in addressing this problem, revealing five distin… ▽ More Classification of gamma-ray bursts (GRBs) has been a long-standing puzzle in high-energy astrophysics. Recent observations challenge the traditional short vs. long viewpoint, where long GRBs are thought to originate from the collapse of massive stars and short GRBs from compact binary mergers. Machine learning (ML) algorithms have been instrumental in addressing this problem, revealing five distinct GRB groups within the Swift/BAT light curve data, two of which are associated with kilonovae (KNe). In this work, we extend our analysis to the Fermi/GBM catalog and identify five clusters using unsupervised ML techniques, consistent with the Swift/BAT results. These five clusters are well separated in fluence-duration plane, hinting at a potential link between fluence, duration and complexities (or structures) in the light curves of GRBs. Further, we confirm two distinct classes of KN-associated GRBs. The presence of GRB 170817A in one of the two KNe-associated clusters lends evidence to the hypothesis that this class of GRBs could potentially be produced by binary neutron star (BNS) mergers. The second KN-associated GRB cluster could potentially originate from NS-BH mergers. Future multimessenger observations of compact binaries in gravitational waves (GWs) and electromagnetic waves can be paramount in understanding these clusters better. △ Less

Submitted 29 August, 2024; v1 submitted 7 June, 2024; originally announced June 2024.

Comments: Accepted for publication in the ApJ

An Optical Gamma-Ray Burst Catalogue with Measured Redshift PART I: Data Release of 535 Gamma-Ray Bursts and Colour Evolution

Authors: M. G. Dainotti, B. De Simone, R. F. Mohideen Malik, V. Pasumarti, D. Levine, N. Saha, B. Gendre, D. Kido, A. M. Watson, R. L. Becerra, S. Belkin, S. Desai, A. C. C. do E. S. Pedreira, U. Das, L. Li, S. R. Oates, S. B. Cenko, A. Pozanenko, A. Volnova, Y. -D. Hu, A. J. Castro-Tirado, N. B. Orange, T. J. Moriya, N. Fraija, Y. Niino , et al. (27 additional authors not shown)

Abstract: We present the largest optical photometry compilation of Gamma-Ray Bursts (GRBs) with redshifts ($z$). We include 64813 observations of 535 events (including upper limits) from 28 February 1997 up to 18 August 2023. We also present a user-friendly web tool \textit{grbLC} which allows users the visualization of photometry, coordinates, redshift, host galaxy extinction, and spectral indices for each… ▽ More We present the largest optical photometry compilation of Gamma-Ray Bursts (GRBs) with redshifts ($z$). We include 64813 observations of 535 events (including upper limits) from 28 February 1997 up to 18 August 2023. We also present a user-friendly web tool \textit{grbLC} which allows users the visualization of photometry, coordinates, redshift, host galaxy extinction, and spectral indices for each event in our database. Furthermore, we have added a Gamma Ray Coordinate Network (GCN) scraper that can be used to collect data by gathering magnitudes from the GCNs. The web tool also includes a package for uniformly investigating colour evolution. We compute the optical spectral indices for 138 GRBs for which we have at least 4 filters at the same epoch in our sample and craft a procedure to distinguish between GRBs with and without colour evolution. By providing a uniform format and repository for the optical catalogue, this web-based archive is the first step towards unifying several community efforts to gather the photometric information for all GRBs with known redshifts. This catalogue will enable population studies by providing light curves (LCs) with better coverage since we have gathered data from different ground-based locations. Consequently, these LCs can be used to train future LC reconstructions for an extended inference of the redshift. The data gathering also allows us to fill some of the orbital gaps from Swift in crucial points of the LCs, e.g., at the end of the plateau emission or where a jet break is identified. △ Less

Submitted 3 June, 2024; v1 submitted 3 May, 2024; originally announced May 2024.

Comments: 20 pages, 16 figures, 2 tables. Submitted to MNRAS, this version matches the third revision. The Online Materials and data will be available after the publication

On $C_n^{(1)}$-Geometric Crystal and its Ultradiscretization

Authors: Erica S. Dinkins, Kailash C. Misra

Abstract: Let $\mathfrak{g}$ be an affine Lie algebra with index set $I = \{0, 1, 2, \cdots , n\}$ and $\mathfrak{g}^L$ be its Langlands dual. It is conjectured that for each Dynkin node $i \in I \setminus \{0\}$ the affine Lie algebra $\mathfrak{g}$ has a positive geometric crystal whose ultra-discretization is isomorphic to the limit of a certain coherent family of perfect crystals for the Langland dual… ▽ More Let $\mathfrak{g}$ be an affine Lie algebra with index set $I = \{0, 1, 2, \cdots , n\}$ and $\mathfrak{g}^L$ be its Langlands dual. It is conjectured that for each Dynkin node $i \in I \setminus \{0\}$ the affine Lie algebra $\mathfrak{g}$ has a positive geometric crystal whose ultra-discretization is isomorphic to the limit of a certain coherent family of perfect crystals for the Langland dual $\mathfrak{g}^L$. In this paper we construct positive geometric crystals for $\mathcal{V}(C_n^{(1)})$ in the level zero fundamental spin $C_n^{(1)}$- module $W(\varpi_n)$ for $n = 2, 3,4$ and show that its ultra-discretization is isomorphic to the limit $B^{n, \infty}$ of a coherent family $\{B^{n, l}\}_{l \geq 1}$ of perfect crystals for the Langland dual $D_n^{(2)}$ which proves the conjecture in these cases. △ Less

Submitted 10 April, 2024; v1 submitted 9 April, 2024; originally announced April 2024.

Probing the Circumstellar Environment of highly luminous type IIn SN ASASSN-14il

Authors: Naveen Dukiya, Anjasha Gangopadhyay, Kuntal Misra, Griffin Hosseinzadeh, K. Azalee Bostroem, Bhavya Ailawadhi, D. Andrew Howell, Stefano Valenti, Iair Arcavi, Curtis McCully, Archana Gupta

Abstract: We present long-term photometric and spectroscopic studies of Circumstellar Material (CSM)-Ejecta interacting supernova (SN) ASASSN-14il in the galaxy PGC 3093694. The SN reaches a peak $r$-band magnitude of $\sim$ $-20.3 \pm 0.2$ mag rivaling SN 2006tf and SN 2010jl. The multiband and the pseudo-bolometric lightcurve show a plateau lasting $\sim 50$ days. Semi-analytical CSM interaction models ca… ▽ More We present long-term photometric and spectroscopic studies of Circumstellar Material (CSM)-Ejecta interacting supernova (SN) ASASSN-14il in the galaxy PGC 3093694. The SN reaches a peak $r$-band magnitude of $\sim$ $-20.3 \pm 0.2$ mag rivaling SN 2006tf and SN 2010jl. The multiband and the pseudo-bolometric lightcurve show a plateau lasting $\sim 50$ days. Semi-analytical CSM interaction models can match the high luminosity and decline rates of the lightcurves but fail to faithfully represent the plateau region and the bumps in the lightcurves. The spectral evolution resembles the typical SNe IIn dominated by CSM interaction, showing blue-continuum and narrow Balmer lines. The lines are dominated by electron scattering at early epochs. The signatures of the underlying ejecta are visible as the broad component in the H$α$ profile from as early as day 50, hinting at asymmetry in the CSM. A narrow component is persistent throughout the evolution. The SN shows remarkable photometric and spectroscopic similarity with SN 2015da. However, the different polarization in ASASSN-14il compared to SN 2015da suggests an alternative viewing angle. The late-time blueshift in the H$α$ profiles supports dust formation in the post-shock CSM or ejecta. The mass-loss rate of 2-7 M$_{\odot} \mathrm{yr}^{-1}$ suggests a Luminous Blue Variable (LBV) progenitor in an eruptive phase for ASASSN-14il. △ Less

Submitted 15 December, 2024; v1 submitted 5 April, 2024; originally announced April 2024.

Comments: 26 pages, 12 figures, 9 tables, published in ApJ

Journal ref: ApJ, Volume 976, 2024, page 86

Language Models Learn Rare Phenomena from Less Rare Phenomena: The Case of the Missing AANNs

Authors: Kanishka Misra, Kyle Mahowald

Abstract: Language models learn rare syntactic phenomena, but the extent to which this is attributable to generalization vs. memorization is a major open question. To that end, we iteratively trained transformer language models on systematically manipulated corpora which were human-scale in size, and then evaluated their learning of a rare grammatical phenomenon: the English Article+Adjective+Numeral+Noun (… ▽ More Language models learn rare syntactic phenomena, but the extent to which this is attributable to generalization vs. memorization is a major open question. To that end, we iteratively trained transformer language models on systematically manipulated corpora which were human-scale in size, and then evaluated their learning of a rare grammatical phenomenon: the English Article+Adjective+Numeral+Noun (AANN) construction (``a beautiful five days''). We compared how well this construction was learned on the default corpus relative to a counterfactual corpus in which AANN sentences were removed. We found that AANNs were still learned better than systematically perturbed variants of the construction. Using additional counterfactual corpora, we suggest that this learning occurs through generalization from related constructions (e.g., ``a few days''). An additional experiment showed that this learning is enhanced when there is more variability in the input. Taken together, our results provide an existence proof that LMs can learn rare grammatical phenomena by generalization from less rare phenomena. Data and code: https://github.com/kanishkamisra/aannalysis. △ Less

Submitted 24 June, 2025; v1 submitted 28 March, 2024; originally announced March 2024.

Comments: Added Corrigendum to correct 4-gram baseline performance and chance performance

SN 2019nyk: A rapidly declining Type II supernova with early interaction signatures

Authors: Raya Dastidar, Giuliano Pignata, Naveen Dukiya, Kuntal Misra, Daichi Hiramatsu, Javier Silva-Farfán, D. Andrew Howell, K. Azalee Bostroem, Mridweeka Singh, Anjasha Gangopadhyay, Amit Kumar, Curtis McCully

Abstract: We present an optical photometric and spectroscopic analysis of the fast-declining hydrogen-rich Type II supernova (SN) 2019nyk. The light curve properties of SN 2019nyk align well with those of other fast-declining Type II SNe, such as SNe 2013by and 2014G. SN 2019nyk exhibits a peak absolute magnitude of -18.09 $\pm$ 0.17 mag in the V band, followed by a rapid decline at 2.84 $\pm$ 0.03 mag (100… ▽ More We present an optical photometric and spectroscopic analysis of the fast-declining hydrogen-rich Type II supernova (SN) 2019nyk. The light curve properties of SN 2019nyk align well with those of other fast-declining Type II SNe, such as SNe 2013by and 2014G. SN 2019nyk exhibits a peak absolute magnitude of -18.09 $\pm$ 0.17 mag in the V band, followed by a rapid decline at 2.84 $\pm$ 0.03 mag (100 d)$^{-1}$ during the recombination phase. The early spectra of SN 2019nyk exhibit high-ionisation emission features as well as narrow H Balmer lines, persisting until 4.1 d since explosion, indicating the presence of circumstellar material (CSM) in close proximity. A comparison of these features with other Type II SNe displaying an early interaction reveals similarities between these features and those observed in SNe 2014G and 2023ixf. We also compared the early spectra to literature models, estimating a mass-loss rate of the order of 10$^{-3}$ M$_\odot$ yr$^{-1}$. Radiation hydrodynamical modelling of the light curve also suggests the mass loss from the progenitor within a short period prior to explosion, totalling 0.16 M$_\odot$ of material within 2900 R$_\odot$ of the progenitor. Furthermore, light curve modelling infers a zero-age main sequence mass of 15 M$_\odot$ for the progenitor, a progenitor radius of 1031 R$_\odot$, and an explosion energy of 1.1 $\times$ 10$^{51}$ erg. △ Less

Submitted 1 March, 2024; originally announced March 2024.

Comments: 18 pages, 23 figures, accepted in A&A

Prompt emission properties of GRB~200613

Authors: Ankur Ghosh, Kuntal Misra, Dimple

Abstract: We study the prompt emission properties of the long duration GRB~200613A using \textit{Fermi}-Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) data. The prompt emission light curve of GRB~200613A reveals a strong peak emission up to $\sim$ 50 s after the burst accompanied by an extended emission up to $\sim$ 470 s similar to that seen in ultra-long GRB light curves. The time-integrated… ▽ More We study the prompt emission properties of the long duration GRB~200613A using \textit{Fermi}-Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) data. The prompt emission light curve of GRB~200613A reveals a strong peak emission up to $\sim$ 50 s after the burst accompanied by an extended emission up to $\sim$ 470 s similar to that seen in ultra-long GRB light curves. The time-integrated spectroscopy shows that the Band function best fits the main emission episode, and the extended emission follows the power-law behaviour because of poor count rates. Due to its high isotropic energy and low peak energy, GRB~200613A lies at the extreme end in both the $E_{\rm p}$--$E_{\rm iso}$ and $E_{\rm p}$--$T_{90}$ plots. In addition to the GBM detection, the \textit{Fermi}-LAT detected the highest energetic photons of 7.56 GeV after 6.2 ks since burst, which lies beyond the maximum synchrotron energy range. △ Less

Submitted 22 January, 2024; originally announced January 2024.