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Phase-resolved Hubble Space Telescope WFC3 Spectroscopy of Weakly-Irradiated Brown Dwarf GD 1400 and Energy Redistribution-Irradiation Trends in Six WD$-$BD Binaries
Authors:
Rachael C. Amaro,
Dániel Apai,
Yifan Zhou,
Joshua D. Lothringer,
Sarah L. Casewell,
Xianyu Tan,
Ben W. P. Lew,
Travis Barman,
Mark S. Marley,
L. C. Mayorga,
Vivien Parmentier
Abstract:
Irradiated brown dwarfs offer a unique opportunity to bridge the gap between stellar and planetary atmospheres. We present high-quality $\mathit{HST}$/WFC3/G141 phase-resolved spectra of the white dwarf + brown dwarf binary GD 1400, covering more than one full rotation of the brown dwarf. Accounting for brightness variations caused by ZZ Ceti pulsations, we revealed weak ($\sim$1\%) phase curve am…
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Irradiated brown dwarfs offer a unique opportunity to bridge the gap between stellar and planetary atmospheres. We present high-quality $\mathit{HST}$/WFC3/G141 phase-resolved spectra of the white dwarf + brown dwarf binary GD 1400, covering more than one full rotation of the brown dwarf. Accounting for brightness variations caused by ZZ Ceti pulsations, we revealed weak ($\sim$1\%) phase curve amplitude modulations originating from the brown dwarf. Sub-band light curve exploration in various bands showed no significant wavelength dependence on amplitude or phase shift. Extracted day- and night-side spectra indicated chemically similar hemispheres, with slightly higher day-side temperatures, suggesting efficient heat redistribution or dominance of radiative escape over atmospheric circulation. A simple radiative and energy redistribution model reproduced observed temperatures well. Cloud-inclusive models fit the day and night spectra better than cloudless models, indicating global cloud coverage. We also begin qualitatively exploring atmospheric trends across six irradiated brown dwarfs, from the now complete "Dancing with Dwarfs" WD$-$BD sample. The trend we find in the day-side/night-side temperature and irradiation levels is consistent with efficient heat redistribution for irradiation levels less than $\sim$10$^9$ ergs/s/cm$^2$ and decreasing efficiency above that level.
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Submitted 9 January, 2025;
originally announced January 2025.
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The only inflated brown dwarf in an eclipsing white dwarf-brown dwarf binary: WD1032+011B
Authors:
Jenni R. French,
Sarah L. Casewell,
Rachael C. Amaro,
Joshua D. Lothringer,
L. C. Mayorga,
Stuart P. Littlefair,
Ben W. P. Lew,
Yifan Zhou,
Daniel Apai,
Mark S. Marley,
Vivien Parmentier,
Xianyu Tan
Abstract:
Due to their short orbital periods and relatively high flux ratios, irradiated brown dwarfs in binaries with white dwarfs offer better opportunities to study irradiated atmospheres than hot Jupiters, which have lower planet-to-star flux ratios. WD1032+011 is an eclipsing, tidally locked white dwarf-brown dwarf binary with a 9950 K white dwarf orbited by a 69.7 M$_{Jup}$ brown dwarf in a 0.09 day o…
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Due to their short orbital periods and relatively high flux ratios, irradiated brown dwarfs in binaries with white dwarfs offer better opportunities to study irradiated atmospheres than hot Jupiters, which have lower planet-to-star flux ratios. WD1032+011 is an eclipsing, tidally locked white dwarf-brown dwarf binary with a 9950 K white dwarf orbited by a 69.7 M$_{Jup}$ brown dwarf in a 0.09 day orbit. We present time-resolved Hubble Space Telescope Wide Field Camera 3 spectrophotometric data of WD1032+011. We isolate the phase-dependent spectra of WD1032+011B, finding a 210 K difference in brightness temperature between the dayside and nightside. The spectral type of the brown dwarf is identified as L1 peculiar, with atmospheric retrievals and comparison to field brown dwarfs showing evidence for a cloud-free atmosphere. The retrieved temperature of the dayside is $1748^{+66}_{-67}$ K, with a nightside temperature of $1555^{+76}_{-62}$ K, showing an irradiation-driven temperature contrast coupled with inefficient heat redistribution from the dayside to the nightside. The brown dwarf radius is inflated, likely due to the constant irradiation from the white dwarf, making it the only known inflated brown dwarf in an eclipsing white dwarf-brown dwarf binary.
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Submitted 10 September, 2024;
originally announced September 2024.
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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…
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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.
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Submitted 31 July, 2024;
originally announced July 2024.
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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…
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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.
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Submitted 31 July, 2024;
originally announced July 2024.
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Time-resolved Hubble Space Telescope Wide Field Camera 3 Spectrophotometry Reveals Inefficient Day-to-Night Heat Redistribution in the Highly Irradiated Brown Dwarf SDSS 1557B
Authors:
Rachael C. Amaro,
Daniel Apai,
Ben W. P. Lew,
Yifan Zhou,
Joshua D. Lothringer,
Sarah L. Casewell,
Xianyu Tan,
Travis Barman,
Mark S. Marley,
L. C. Mayorga,
Vivien Parmentier
Abstract:
Brown dwarfs in ultra-short period orbits around white dwarfs offer a unique opportunity to study the properties of tidally-locked, fast rotating (1-3 hr), and highly-irradiated atmospheres. Here, we present phase-resolved spectrophotometry of the white dwarf-brown dwarf (WD-BD) binary SDSS 1557, which is the fifth WD-BD binary in our six-object sample. Using the Hubble Space Telescope Wide Field…
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Brown dwarfs in ultra-short period orbits around white dwarfs offer a unique opportunity to study the properties of tidally-locked, fast rotating (1-3 hr), and highly-irradiated atmospheres. Here, we present phase-resolved spectrophotometry of the white dwarf-brown dwarf (WD-BD) binary SDSS 1557, which is the fifth WD-BD binary in our six-object sample. Using the Hubble Space Telescope Wide Field Camera 3 Near-infrared G141 instrument, the 1.1 to 1.7 $μ$m phase curves show rotational modulations with semi-amplitudes of 10.5$\pm$0.1%. We observe a wavelength dependent amplitude, with longer wavelengths producing larger amplitudes, while no wavelength dependent phase shifts were identified. The phase-resolved extracted BD spectra exhibit steep slopes and are nearly featureless. A simple radiative energy redistribution atmospheric model recreates the hemisphere integrated brightness temperatures at three distinct phases and finds evidence for weak redistribution efficiency. Our model also predicts a higher inclination than previously published. We find that SDSS 1557B, the second most irradiated BD in our sample, is likely dominated by clouds on the night side, whereas the featureless day side spectrum is likely dominated by H$^-$ opacity and a temperature inversion, much like the other highly-irradiated BD EPIC2122B.
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Submitted 11 April, 2024;
originally announced April 2024.
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A Modest Proposal for the Non-existence of Exoplanets: The Expansion of Stellar Physics to Include Squars
Authors:
Charity Woodrum,
Raphael E. Hviding,
Rachael C. Amaro,
Katie Chamberlain
Abstract:
The search for exoplanets has become a focal point of astronomical research, captivating public attention and driving scientific inquiry; however, the rush to confirm exoplanet discoveries has often overlooked potential alternative explanations leading to a scientific consensus that is overly reliant on untested assumptions and limited data. We argue that the evidence in support of exoplanet obser…
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The search for exoplanets has become a focal point of astronomical research, captivating public attention and driving scientific inquiry; however, the rush to confirm exoplanet discoveries has often overlooked potential alternative explanations leading to a scientific consensus that is overly reliant on untested assumptions and limited data. We argue that the evidence in support of exoplanet observation is not necessarily definitive and that alternative interpretations are not only possible, but necessary. Our conclusion is therefore concise: exoplanets do not exist. Here, we present the framework for a novel type of cuboid star, or squar, which can precisely reproduce the full range of observed phenomena in stellar light curves, including the trapezoidal flux deviations (TFDs) often attributed to "exoplanets." In this discovery paper, we illustrate the power of the squellar model, showing that the light curve of the well-studied "exoplanet" WASP-12b can be reconstructed simply from a rotating squar with proportions $1:1/8:1$, without invoking ad-hoc planetary bodies. Our findings cast serious doubt on the validity of current "exoplanetary" efforts, which have largely ignored the potential role of squars and have instead blindly accepted the exoplanet hypothesis without sufficient critical scrutiny. In addition, we discuss the sociopolitical role of climate change in spurring the current exoplanet fervor which has lead to the speculative state of "exoplanetary science" today. We strongly urge the astronomical community to take our model proposal seriously and treat its severe ramifications with the utmost urgency to restore rationality to the field of astronomy.
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Submitted 29 March, 2023;
originally announced March 2023.
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Hotter Than Expected: HST/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux
Authors:
Rachael C. Amaro,
Daniel Apai,
Yifan Zhou,
Ben W. P. Lew,
Sarah L. Casewell,
L. Mayorga,
Mark S. Marley,
Xianyu Tan,
Joshua D. Lothringer,
Vivien Parmentier,
Travis Barman
Abstract:
With infrared flux contrasts larger than typically seen in hot Jupiter, tidally-locked white dwarf-brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M$_{BD}$ = 52 $\pm$ 3 M$_{Jup}$ brown dwarf orbiting a T$_{eff}$ = 7756 $\pm$ 35 K white dwarf with an ultra-short period of $\sim$102 min. We present HS…
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With infrared flux contrasts larger than typically seen in hot Jupiter, tidally-locked white dwarf-brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M$_{BD}$ = 52 $\pm$ 3 M$_{Jup}$ brown dwarf orbiting a T$_{eff}$ = 7756 $\pm$ 35 K white dwarf with an ultra-short period of $\sim$102 min. We present HST/WFC3 spectroscopic phase curves of NLTT5306, consisting of 47 spectra from 1.1 to 1.7 microns with an average S/N=65 per wavelength. We extracted the phase-resolved spectra of the brown dwarf NLTT5306B, finding a small (<100 K) day/night temperature difference ($\sim$5 percent of the average day-side temperature). Our best-fit model phase curves revealed a complex wavelength-dependence on amplitudes and relative phase offsets, suggesting longitudinal-vertical atmospheric structure. The night-side spectrum was well-fit by a cloudy, non-irradiated atmospheric model while the day-side was best-matched by a cloudy, weakly irradiated model. Additionally, we created a simple radiative energy redistribution model of the atmosphere and found evidence for efficient day-to-night heat redistribution and a moderately high Bond albedo. We also discovered an internal heat flux much higher than expected given the published system age, leading to an age reassessment that resulted in NLTT5306B most likely being much younger. We find that NLTT5306B is the only known significantly irradiated brown dwarf where the global temperature structure is not dominated by external irradiation, but rather its own internal heat. Our study provides an essential insight into the drivers of global circulation and day-to-night heat transport as a function of irradiation, rotation rate, and internal heat.
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Submitted 13 March, 2023;
originally announced March 2023.
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Circumstellar Medium Interaction in SN 2018lab, A Low-Luminosity II-P Supernova observed with TESS
Authors:
Jeniveve Pearson,
Griffin Hosseinzadeh,
David J. Sand,
Jennifer E. Andrews,
Jacob E. Jencson,
Yize Dong,
K. Azalee Bostroem,
Stefano Valenti,
Daryl Janzen,
Nicolás Meza Retamal,
Michael J. Lundquist,
Samuel Wyatt,
Rachael C. Amaro,
Jamison Burke,
D. Andrew Howell,
Curtis McCully,
Daichi Hiramatsu,
Saurabh W. Jha,
Nathan Smith,
Joshua Haislip,
Vladimir Kouprianov,
Daniel E. Reichart,
Yi Yang,
Jeonghee Rho
Abstract:
We present photometric and spectroscopic data of SN 2018lab, a low luminosity type IIP supernova (LLSN) with a V-band peak luminosity of $-15.1\pm0.1$ mag. SN 2018lab was discovered by the Distance Less Than 40 Mpc (DLT40) SNe survey only 0.73 days post-explosion, as determined by observations from the Transiting Exoplanet Survey Satellite (TESS). TESS observations of SN 2018lab yield a densely sa…
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We present photometric and spectroscopic data of SN 2018lab, a low luminosity type IIP supernova (LLSN) with a V-band peak luminosity of $-15.1\pm0.1$ mag. SN 2018lab was discovered by the Distance Less Than 40 Mpc (DLT40) SNe survey only 0.73 days post-explosion, as determined by observations from the Transiting Exoplanet Survey Satellite (TESS). TESS observations of SN 2018lab yield a densely sampled, fast-rising, early time light curve likely powered by circumstellar medium (CSM) interaction. The blue-shifted, broadened flash feature in the earliest spectra ($<$2 days) of SN 2018lab provide further evidence for ejecta-CSM interaction. The early emission features in the spectra of SN 2018lab are well described by models of a red supergiant progenitor with an extended envelope and close-in CSM. As one of the few LLSNe with observed flash features, SN 2018lab highlights the need for more early spectra to explain the diversity of flash feature morphology in type II SNe.
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Submitted 7 March, 2023; v1 submitted 30 August, 2022;
originally announced August 2022.
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Early Lightcurves of Type Ia Supernovae are Consistent with Nondegenerate Progenitor Companions
Authors:
J. Burke,
D. A. Howell,
D. J. Sand,
R. C. Amaro,
P. J. Brown,
J. E. Andrews,
K. A. Bostroem,
Y. Dong,
J. Haislip,
D. Hiramatsu,
G. Hosseinzadeh,
V. Kouprianov,
M. J. Lundquist,
C. McCully,
C. Pellegrino,
D. Reichart,
L. Tartaglia,
S. Valenti,
S. Yang
Abstract:
If Type Ia supernovae (SNe~Ia) result from a white dwarf being ignited by Roche lobe overflow from a nondegenerate companion, then as the supernova explosion runs into the companion star its ejecta will be shocked, causing an early blue excess in the lightcurve. A handful of these excesses have been found in single-object studies, but inferences about the population of SNe~Ia as a whole have been…
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If Type Ia supernovae (SNe~Ia) result from a white dwarf being ignited by Roche lobe overflow from a nondegenerate companion, then as the supernova explosion runs into the companion star its ejecta will be shocked, causing an early blue excess in the lightcurve. A handful of these excesses have been found in single-object studies, but inferences about the population of SNe~Ia as a whole have been limited because of the rarity of multiwavelength followup within days of explosion. Here we present a three-year investigation yielding an unbiased sample of nine nearby ($z<0.01$) SNe~Ia with exemplary early data. The data are truly multiwavelength, covering $UBVgri$ and Swift bandpasses, and also early, with an average first epoch 16.0 days before maximum light. Of the nine objects, three show early blue excesses. We do not find enough statistical evidence to reject the null hypothesis that SNe~Ia predominantly arise from Roche-lobe-overflowing single-degenerate systems ($p=0.94$). When looking at the objects' colors, we find the objects are almost uniformly near-UV-blue, in contrast to earlier literature samples which found that only a third of SNe~Ia are near-UV-blue, and we find a seemingly continuous range of $B-V$ colors in the days after explosion, again in contrast with earlier claims in the literature. This study highlights the importance of early, truly multiwavelength, high-cadence data in determining the progenitor systems of SNe~Ia and in revealing their diverse early behavior.
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Submitted 15 July, 2022;
originally announced July 2022.
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High Cadence TESS and ground-based data of SN 2019esa, the less energetic sibling of SN 2006gy
Authors:
Jennifer E. Andrews,
Jeniveve Pearson,
M. J. Lundquist,
David J. Sand,
Jacob E. Jencson,
K. Azalee Bostroem,
Griffin Hosseinzadeh,
S. Valenti,
Nathan Smith,
R. C. Amaro,
Yize Dong,
Daryl Janzen,
Nicolas Meza,
Samuel Wyatt,
Jamison Burke,
Daichi Hiramatsu,
D. Andrew Howell,
Curtis McCully,
Craig Pellegrino
Abstract:
We present photometric and spectroscopic observations of the nearby ($D\approx28$ Mpc) interacting supernova (SN) 2019esa, discovered within hours of explosion and serendipitously observed by the Transiting Exoplanet Survey Satellite (TESS). Early, high cadence light curves from both TESS and the DLT40 survey tightly constrain the time of explosion, and show a 30 day rise to maximum light followed…
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We present photometric and spectroscopic observations of the nearby ($D\approx28$ Mpc) interacting supernova (SN) 2019esa, discovered within hours of explosion and serendipitously observed by the Transiting Exoplanet Survey Satellite (TESS). Early, high cadence light curves from both TESS and the DLT40 survey tightly constrain the time of explosion, and show a 30 day rise to maximum light followed by a near constant linear decline in luminosity. Optical spectroscopy over the first 40 days revealed a highly reddened object with narrow Balmer emission lines seen in Type IIn supernovae. The slow rise to maximum in the optical lightcurve combined with the lack of broad H$α$ emission suggest the presence of very optically thick and close circumstellar material (CSM) that quickly decelerated the supernova ejecta. This CSM was likely created from a massive star progenitor with an $\dot{M}$ $\sim$ 0.3 M$_{\odot}$ yr$^{-1}$ lost in a previous eruptive episode 3--4 years before eruption, similar to giant eruptions of luminous blue variable stars. At late times, strong intermediate-width Ca II, Fe I, and Fe II lines are seen in the optical spectra, identical to those seen in the superluminous interacting SN 2006gy. The strong CSM interaction masks the underlying explosion mechanism in SN 2019esa, but the combination of the luminosity, strength of the H$α$ lines, and mass loss rate of the progenitor all point to a core collapse origin.
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Submitted 24 May, 2022;
originally announced May 2022.
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Nebular-Phase Spectra of Type Ia Supernovae from the Las Cumbres Observatory Global Supernova Project
Authors:
M. L. Graham,
T. D. Kennedy,
S. Kumar,
R. C. Amaro,
D. J. Sand,
S. W. Jha,
L. Galbany,
J. Vinko,
J. C. Wheeler,
E. Y. Hsiao,
K. A. Bostroem,
J. Burke,
D. Hiramatsu,
G. Hosseinzadeh,
C. McCully,
D. A. Howell,
T. Diamond,
P. Hoeflich,
X. Wang,
W. Li
Abstract:
The observed diversity in Type Ia supernovae (SNe Ia) -- the thermonuclear explosions of carbon-oxygen white dwarf stars used as cosmological standard candles -- is currently met with a variety of explosion models and progenitor scenarios. To help improve our understanding of whether and how often different models contribute to the occurrence of SNe Ia and their assorted properties, we present a c…
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The observed diversity in Type Ia supernovae (SNe Ia) -- the thermonuclear explosions of carbon-oxygen white dwarf stars used as cosmological standard candles -- is currently met with a variety of explosion models and progenitor scenarios. To help improve our understanding of whether and how often different models contribute to the occurrence of SNe Ia and their assorted properties, we present a comprehensive analysis of seven nearby SNe Ia. We obtained one to two epochs of optical spectra with Gemini Observatory during the nebular phase ($>$200 days past peak) for each of these events, all of which had time-series of photometry and spectroscopy at early times (the first $\sim$8 weeks after explosion). We use the combination of early- and late-time observations to assess the predictions of various models for the explosion (e.g., double-detonation, off-center detonation, stellar collisions), progenitor star (e.g., ejecta mass, metallicity), and binary companion (e.g., another white dwarf or a non-degenerate star). Overall, we find general consistency in our observations with spherically-symmetric models for SN Ia explosions, and with scenarios in which the binary companion is another degenerate star. We also present an in-depth analysis of SN 2017fzw, a member of the sub-group of SNe Ia which appear to be transitional between the subluminous "91bg-like" events and normal SNe Ia, and for which nebular-phase spectra are rare.
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Submitted 19 January, 2022;
originally announced January 2022.
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AT 2019qyl in NGC 300: Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary
Authors:
Jacob E. Jencson,
Jennifer E. Andrews,
Howard E. Bond,
Viraj Karambelkar,
David J. Sand,
Schuyler D. van Dyk,
Nadejda Blagorodnova,
Martha L. Boyer,
Mansi M. Kasliwal,
Ryan M. Lau,
Shazrene Mohamed,
Robert Williams,
Patricia A. Whitelock,
Rachael C. Amaro,
K. Azalee Bostroem,
Yize Dong,
Michael J. Lundquist,
Stefano Valenti,
Samuel D. Wyatt,
Jamie Burke,
Kishalay De,
Saurabh W. Jha,
Joel Johansson,
César Rojas-Bravo,
David A. Coulter
, et al. (17 additional authors not shown)
Abstract:
Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered astrophysical transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in the nearby Sculptor Group galaxy NGC 300. The light curve shows a rapid rise lasting…
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Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered astrophysical transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in the nearby Sculptor Group galaxy NGC 300. The light curve shows a rapid rise lasting $\lesssim 1$ day, reaching a peak absolute magnitude of $M_V = -9.2$ mag, and a very fast decline, fading by 2 mag over 3.5 days. A steep dropoff in the light curves after 71 days and the rapid decline timescale suggest a low-mass ejection from a massive WD with $M_{\rm WD} \gtrsim 1.2~M_{\odot}$. We present an unprecedented view of the early spectroscopic evolution of such an event. Three spectra prior to the peak reveal a complex, multicomponent outflow giving rise to internal collisions and shocks in the ejecta of an He/N-class nova. We identify a coincident IR-variable counterpart in the extensive preeruption coverage of the transient location and infer the presence of a symbiotic progenitor system with an O-rich asymptotic-giant-branch donor star, as well as evidence for an earlier UV-bright outburst in 2014. We suggest that AT 2019qyl is analogous to the subset of Galactic recurrent novae with red-giant companions such as RS Oph and other embedded nova systems like V407 Cyg. Our observations provide new evidence that internal shocks between multiple, distinct outflow components likely contribute to the generation of the shock-powered emission from such systems.
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Submitted 5 September, 2021; v1 submitted 22 February, 2021;
originally announced February 2021.
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A Bright Ultraviolet Excess in the Transitional 02es-like Type Ia Supernova 2019yvq
Authors:
J. Burke,
D. A. Howell,
S. K. Sarbadhicary,
D. J. Sand,
R. C. Amaro,
D. Hiramatsu,
C. McCully,
C. Pellegrino,
J. E. Andrews,
P. J. Brown,
Koichi Itagaki,
M. Shahbandeh,
K. A. Bostroem,
L. Chomiuk,
E. Y. Hsiao,
Nathan Smith,
S. Valenti
Abstract:
We present photometric and spectroscopic observations of the nearby Type Ia SN 2019yvq, from its discovery $\sim$1 day after explosion to $\sim$100 days after its peak brightness. This SN exhibits several unusual features, most notably an extremely bright UV excess seen within $\sim$5 days of its explosion. As seen in Swift UV data, this early excess outshines its "peak" brightness, making this ob…
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We present photometric and spectroscopic observations of the nearby Type Ia SN 2019yvq, from its discovery $\sim$1 day after explosion to $\sim$100 days after its peak brightness. This SN exhibits several unusual features, most notably an extremely bright UV excess seen within $\sim$5 days of its explosion. As seen in Swift UV data, this early excess outshines its "peak" brightness, making this object more extreme than other SNe with early UV/blue excesses (e.g. iPTF14atg and SN 2017cbv). In addition, it was underluminous ($M_B=-18.4$), relatively quickly declining ($Δm_{15}(B)=1.35$), and shows red colors past its early blue bump. Unusual (although not unprecedented) spectral features include extremely broad-lined and high-velocity Si absorption. Despite obvious differences in peak spectra, we classify SN 2019yvq as a transitional member of the 02es-like subclass due to its similarities in several respects (e.g. color, peak luminosity, peak Ti, nebular [Ca II]). We model this dataset with a variety of published models, including SN ejecta - companion shock interaction and sub-Chandrasekhar mass WD double detonation models. Radio constraints from the VLA place an upper limit of $(4.5 - 20) \times 10^{-8}$ M$_{\odot}$/yr on the mass-loss rate from a symbiotic progenitor, which does not exclude a red giant or main sequence companion. Ultimately we find that no one model can accurately replicate all aspects of the dataset, and further we find that the ubiquity of early excesses in 02es-like SNe Ia requires a progenitor system that is capable of producing isotropic UV flux, ruling out some models for this class of objects.
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Submitted 15 January, 2021;
originally announced January 2021.
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Searches after Gravitational Waves Using ARizona Observatories (SAGUARO): Observations and Analysis from Advanced LIGO/Virgo's Third Observing Run
Authors:
K. Paterson,
M. J. Lundquist,
J. C. Rastinejad,
W. Fong,
D. J. Sand,
J. E. Andrews,
R. C. Amaro,
O. Eskandari,
S. Wyatt,
P. N. Daly,
H. Bradley,
S. Zhou-Wright,
S. Valenti,
S. Yang,
E. Christensen,
A. R. Gibbs,
F. Shelly,
C. Bilinski,
L. Chomiuk,
A. Corsi,
M. R. Drout,
R. J. Foley,
P. Gabor,
P. Garnavich,
C. J. Grier
, et al. (12 additional authors not shown)
Abstract:
With the conclusion of the third observing run for Advanced LIGO/Virgo (O3), we present a detailed analysis of both triggered and serendipitous observations of 17 gravitational wave (GW) events (7 triggered and 10 purely serendipitous) from the Searches After Gravitational-waves Using ARizona Observatories (SAGUARO) program. We searched a total of 4935 deg$^2$ down to a median 5$σ$ transient detec…
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With the conclusion of the third observing run for Advanced LIGO/Virgo (O3), we present a detailed analysis of both triggered and serendipitous observations of 17 gravitational wave (GW) events (7 triggered and 10 purely serendipitous) from the Searches After Gravitational-waves Using ARizona Observatories (SAGUARO) program. We searched a total of 4935 deg$^2$ down to a median 5$σ$ transient detection depth of 21.1 AB mag using the Mt Lemmon 1.5 m telescope, the discovery engine for SAGUARO. In addition to triggered events within 24~hours, our transient search encompassed a time interval following GW events of $<120$~hrs, providing observations on $\sim$ 1/2 of the events accessible to the Mt Lemmon 1.5 m telescope. We covered 2.1--86\% of the LVC total probability ($P_{\rm total}$) for individual events, with a median $P_{\rm total} \approx 8\%$ within $<120$~hours. Following improvements to our pipeline and the addition of serendipitous observations, we find a total of 7 new optical candidates across 5 GW events which we are unable to rule out after searching for additional information and comparing to kilonova models. Using both publicly available and our own late-time data, we investigated a total of 252 optical candidates for these 17 events, finding only 65\% were followed up in some capacity by the community. Of the total 252 candidates, we are able to rule out an additional 12 previously reported counterpart candidates. In light of these results, we discuss lessons learned from the SAGUARO GW counterpart search. We discuss how community coordination of observations and candidate follow-up, as well as the role of archival data, are crucial to improving the efficiency of follow-up efforts and preventing unnecessary duplication of effort with limited EM resources.
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Submitted 21 December, 2020;
originally announced December 2020.
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The luminous red nova variety: AT 2020hat and AT 2020kog
Authors:
A. Pastorello,
G. Valerin,
M. Fraser,
N. Elias-Rosa,
S. Valenti,
A. Reguitti,
P. A. Mazzali,
R. C. Amaro,
J. E. Andrews,
Y. Dong,
J. Jencson,
M. Lundquist,
D. E. Reichart,
D. J. Sand,
S. Wyatt,
S. J. Smartt,
K. W. Smith,
S. Srivastav,
Y. -Z. Cai,
E. Cappellaro,
S. Holmbo,
A. Fiore,
D. Jones,
E. Kankare,
E. Karamehmetoglu
, et al. (10 additional authors not shown)
Abstract:
We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise, lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectros…
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We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise, lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at ~7 x 10^40 erg/s, while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type IIn supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37 d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km/s, along with an Halpha emission with a full-width at half-maximum velocity of 250 km/s. For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the Hubble Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of MF606W = -3.33+-0.09 mag and a colour of F606W-F814W = 1.14+-0.05 mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.
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Submitted 14 January, 2021; v1 submitted 20 November, 2020;
originally announced November 2020.
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Supernova 2018cuf: A Type IIP supernova with a slow fall from plateau
Authors:
Yize Dong,
S. Valenti,
K. A. Bostroem,
D. J. Sand,
Jennifer E. Andrews,
L. Galbany,
Saurabh W. Jha,
Youssef Eweis,
Lindsey Kwok,
E. Y. Hsiao,
Scott Davis,
Peter J. Brown,
H. Kuncarayakti,
Keiichi Maeda,
Jeonghee Rho,
R. C. Amaro,
J. P. Anderson,
Iair Arcavi,
Jamison Burke,
Raya Dastidar,
"Gastón Folatelli",
Joshua Haislip,
Daichi Hiramatsu,
Griffin Hosseinzadeh,
D. Andrew Howell
, et al. (12 additional authors not shown)
Abstract:
We present multi-band photometry and spectroscopy of SN 2018cuf, a Type IIP ("P" for plateau) supernova (SN) discovered by the Distance Less Than 40 Mpc survey (DLT40) within 24 hours of explosion. SN 2018cuf appears to be a typical Type IIP SN, with an absolute $V$-band magnitude of $-$16.73 $\pm$ 0.32 at maximum and a decline rate of 0.21 $\pm$ 0.05 mag/50d during the plateau phase. The distance…
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We present multi-band photometry and spectroscopy of SN 2018cuf, a Type IIP ("P" for plateau) supernova (SN) discovered by the Distance Less Than 40 Mpc survey (DLT40) within 24 hours of explosion. SN 2018cuf appears to be a typical Type IIP SN, with an absolute $V$-band magnitude of $-$16.73 $\pm$ 0.32 at maximum and a decline rate of 0.21 $\pm$ 0.05 mag/50d during the plateau phase. The distance of the object is constrained to be 41.8 $\pm$ 5.7 Mpc by using the expanding photosphere method. We use spectroscopic and photometric observations from the first year after the explosion to constrain the progenitor of SN 2018cuf using both hydrodynamic light curve modelling and late-time spectroscopic modelling. The progenitor of SN 2018cuf was most likely a red supergiant of about 14.5 $\rm M_{\odot}$ that produced 0.04 $\pm$ 0.01 $\rm M_{\odot}$ $\rm ^{56}Ni$ during the explosion. We also found $\sim$ 0.07 $\rm M_{\odot}$ of circumstellar material (CSM) around the progenitor is needed to fit the early light curves, where the CSM may originate from pre-supernova outbursts. During the plateau phase, high velocity features at $\rm \sim 11000\ km~s^{-1}$ are detected both in the optical and near-infrared spectra, supporting the possibility that the ejecta were interacting with some CSM. A very shallow slope during the post-plateau phase is also observed and it is likely due to a low degree of nickel mixing or the relatively high nickel mass in the SN.
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Submitted 19 October, 2020;
originally announced October 2020.
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Discovery and Rapid Follow-up Observations of the Unusual Type II SN 2018ivc in NGC 1068
Authors:
K. A. Bostroem,
S. Valenti,
D. J. Sand,
J. E. Andrews,
S. D. Van Dyk,
L. Galbany,
D. Pooley,
R. C. Amaro,
N. Smith,
S. Yang,
G. C. Anupama,
I. Arcavi,
E. Baron,
P. J. Brown,
J. Burke,
R. Cartier,
D. Hiramatsu,
Y. Dong,
E. Egami,
S. Ertel,
A. V. Filippenko,
O. D. Fox,
J. Haislip,
G. Hosseinzadeh,
D. A. Howell
, et al. (22 additional authors not shown)
Abstract:
We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D=10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 30 days of evolution. This rapidly changing light curve indicates that interaction between the circumstellar material and…
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We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D=10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 30 days of evolution. This rapidly changing light curve indicates that interaction between the circumstellar material and ejecta plays a significant role in the evolution. Circumstellar interaction is further supported by a strong X-ray detection. The spectra are rapidly evolving and dominated by hydrogen, helium, and calcium emission lines. We identify a rare high-velocity emission-line feature blueshifted at ~7800 km/s (in Ha, Hb, Pb, Pg, HeI, CaII), which is visible from day 18 until at least day 78 and could be evidence of an asymmetric progenitor or explosion. From the overall similarity between SN 2018ivc and SN 1996al, the \Ha{} equivalent width of its parent HII region, and constraints from pre-explosion archival Hubble Space Telescope images, we find that the progenitor of SN 2018ivc could be as massive as 52 Msun but is more likely <12 Msun. SN 2018ivc demonstrates the importance of the early discovery and rapid follow-up observations of nearby supernovae to study the physics and progenitors of these cosmic explosions.
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Submitted 27 May, 2020; v1 submitted 16 September, 2019;
originally announced September 2019.
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Searches After Gravitational-waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo's Third Observing Run
Authors:
M. J. Lundquist,
K. Paterson,
W. Fong,
D. J. Sand,
J. E. Andrews,
I. Shivaei,
P. N. Daly,
S. Valenti,
S. Yang,
E. Christensen,
A. R. Gibbs,
F. Shelly,
S. Wyatt,
O. Kuhn,
R. C. Amaro,
I. Arcavi,
P. Behroozi,
N. Butler,
L. Chomiuk,
A. Corsi,
M. R. Drout,
E. Egami,
X. Fan,
R. J. Foley,
B. Frye
, et al. (31 additional authors not shown)
Abstract:
We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter, located primarily in the Northern Hemisphere. We provide an overview of SAGUARO's telescopic resources, pi…
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We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter, located primarily in the Northern Hemisphere. We provide an overview of SAGUARO's telescopic resources, pipeline for transient detection, and database for candidate visualization. We describe SAGUARO's discovery component, which utilizes the $5$~deg$^2$ field-of-view optical imager on the Mt. Lemmon 1.5m telescope, reaching limits of $\approx 21.3$~AB mag while rapidly tiling large areas. We also describe the follow-up component of SAGUARO, used for rapid vetting and monitoring of optical candidates. With the onset of Advanced LIGO/Virgo's third observing run, we present results from the first three SAGUARO searches following the GW events S190408an, S190425z and S190426c, which serve as a valuable proof-of-concept of SAGUARO. We triggered and searched 15, 60 and 60 deg$^{2}$ respectively, 17.6, 1.4 and 41.8 hrs after the initial GW alerts. We covered 7.8, 3.0 and 5.1\% of the total probability within the GW event localizations, reaching 3$σ$ limits of 19.8, 21.3 and 20.8 AB mag, respectively. Although no viable counterparts associated with these events were found, we recovered 6 known transients and ruled out 5 potential candidates. We also present Large Binocular Telescope spectroscopy of PS19eq/SN2019ebq, a promising kilonova candidate that was later determined to be a supernova. With the ability to tile large areas and conduct detailed follow-up, SAGUARO represents a significant addition to GW counterpart searches.
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Submitted 17 July, 2019; v1 submitted 14 June, 2019;
originally announced June 2019.
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Nebular H$α$ Limits for Fast Declining Type Ia Supernovae
Authors:
D. J. Sand,
R. C. Amaro,
M. Moe,
M. L. Graham,
J. E. Andrews,
J. Burke,
R. Cartier,
Y. Eweis,
L. Galbany,
D. Hiramatsu,
D. A. Howell,
S. W. Jha,
M. Lundquist,
T. Matheson,
C. McCully,
P. Milne,
Nathan Smith,
S. Valenti,
S. Wyatt
Abstract:
One clear observational prediction of the single degenerate progenitor scenario as the origin of type Ia supernovae (SNe) is the presence of relatively narrow ($\approx$1000 km s$^{-1}$) H$α$ emission at nebular phases, although this feature is rarely seen. We present a compilation of nebular phase H$α$ limits for SN Ia in the literature and demonstrate that this heterogenous sample has been biase…
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One clear observational prediction of the single degenerate progenitor scenario as the origin of type Ia supernovae (SNe) is the presence of relatively narrow ($\approx$1000 km s$^{-1}$) H$α$ emission at nebular phases, although this feature is rarely seen. We present a compilation of nebular phase H$α$ limits for SN Ia in the literature and demonstrate that this heterogenous sample has been biased towards SN Ia with relatively high luminosities and slow decline rates, as parameterized by $Δ$m$_{15}(B)$, the difference in $B$-band magnitude between maximum light and fifteen days afterward. Motivated by the need to explore the full parameter space of SN~Ia and their subtypes, we present two new and six previously published nebular spectra of SN Ia with $Δ$m$_{15}(B)$$ > $1.3 mag (including members of the transitional and SN1991bg-like subclasses) and measure nondetection limits of $L_{Hα}$$~<~$0.85--9.9$\times$10$^{36}$ ergs s$^{-1}$, which we confirmed by implanting simulated H$α$ emission into our data. Based on the lastest models of swept-up material stripped from a nondegenerate companion star, these $L_{Hα}$ values correspond to hydrogen mass limits of $M_H$$~\lesssim~$1-3$\times$10$^{-4}$ $M_{\odot}$, roughly three orders of magnitude below that expected for the systems modeled, although we note that no simulations of H$α$ nebular emission in such weak explosions have yet been performed. Despite the recent detection of strong H$α$ in ASASSN-18tb (SN 2018fhw; $Δ$m$_{15}(B)$ = 2.0 mag), we see no evidence that fast declining systems are more likely to have late time H$α$ emission, although a larger sample is needed to confirm this result.
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Submitted 5 May, 2019; v1 submitted 8 March, 2019;
originally announced March 2019.