Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631

Abstract

We present an observational study of the luminous red nova (LRN) AT\,2021biy in the nearby galaxy NGC\,4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from $\sim 231$\,days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT\,2021biy shows a short-duration blue peak, with a bolometric luminosity of $\sim 1.6\times 10^{41}$\,erg\,s${}^{-1}$, followed by the longest plateau among LRNe to date, with a duration of 210\,days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT\,2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum ($T_{\mathrm{BB}}\approx 2050$ K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT\,2021biy has local dust properties similar to those of V838\,Mon in the Milky Way Galaxy. Inspection of archival {\it Hubble Space Telescope} data taken on 2003 August 3 reveals a $\sim 20$\,\msun\ progenitor candidate with log\,$(L/{\mathrm{L}}_{\odot })=5.0$\,dex and $T_{\mathrm{eff}}=5900$\,K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17--24\,\msun\ primary component.

arXiv comment21 pages, 14 figures. Accepted by Astronomy and Astrophysics

References in corpus (106)

• emcee: The MCMC Hammer
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• ATLAS: A High-Cadence All-Sky Survey System
• Las Cumbres Observatory Global Telescope Network
• The Fourth Data Release of the Sloan Digital Sky Survey
• Common Envelope Evolution: Where we stand and how we can move forward
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• WISeREP - An Interactive Supernova Data Repository
• Reevaluating Old Stellar Populations
• The Thirteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey MApping Nearby Galaxies at Apache Point Observatory
• V1309 Scorpii: merger of a contact binary
• An Empirical Relation between Sodium Absorption and Dust Extinction
• An H-alpha Imaging Survey of Galaxies in the Local 11 Mpc Volume
• The SCORPIO focal reducer
• Detection of circumstellar material in a normal Type Ia Supernova
• Design and operation of the ATLAS Transient Science Server
• Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia Supernovae
• Pan-STARRS Photometric and Astrometric Calibration
• Oxygen and nitrogen abundances in nearby galaxies. Correlations between oxygen abundance and macroscopic properties
• The Supernova Channel of Super-AGB Stars
• The ATLAS All-Sky Stellar Reference Catalog
• Super and massive AGB stars - IV. Final fates - Initial to final mass relation
• Low Luminosity Type II Supernovae: Spectroscopic and Photometric Evolution
• SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared
• Fully-Automated Reduction of Longslit Spectroscopy with the Low Resolution Imaging Spectrometer at Keck Observatory
• Discovery of the Dust-Enshrouded Progenitor of SN 2008S with Spitzer
• A New Class of Luminous Transients and A First Census of Their Massive Stellar Progenitors
• SN 2008S: an electron capture SN from a super-AGB progenitor?
• Underluminous Type II Plateau Supernovae: II. Pointing towards moderate mass precursors
• The Abundance Properties of Nearby Late-Type Galaxies.I. The Data
• The mysterious eruption of V838 Mon
• Main-sequence stellar eruption model for V838 Mon
• SN 2005cs in M51 I. The first month of evolution of a subluminous SN II plateau
• An unusually brilliant transient in the galaxy Messier 85
• Super-AGB Stars and their role as Electron Capture Supernova progenitors
• Identification of the Long-Sought Common-Envelope Events
• Variety in Supernovae
• An Intermediate Luminosity Transient in NGC300: The Eruption of a Dust-Enshrouded Massive Star
• Eruptions of the V838 Mon type: stellar merger versus nuclear outburst models
• Stellar Mergers Are Common
• Optimization of the Observing Cadence for the Rubin Observatory Legacy Survey of Space and Time: a pioneering process of community-focused experimental design
• YBC, a stellar bolometric corrections database with variable extinction coefficients: an application to PARSEC isochrones
• Cool and Luminous Transients from Mass-Losing Binary Stars
• V1309 SCO - Understanding a merger
• Setting UBVRI Photometric Zero-Points Using Sloan Digital Sky Survey ugriz Magnitudes
• Nova Sagittarii 1994 #1 (V4332 Sagittarii): The Discovery and Evolution of an Unusual Luminous Red Variable Star
• Binary Stellar Mergers with Marginally-Bound Ejecta: Excretion Disks, Inflated Envelopes, Outflows, and their Luminous Transients
• Luminous Red Novae: Stellar Mergers or Giant Eruptions?
• Shock-powered light curves of luminous red novae as signatures of pre-dynamical mass loss in stellar mergers
• Common Envelope ejection for a Luminous Red Nova in M101
• The GHOSTS survey. II. The diversity of Halo Color and Metallicity Profiles of Massive Disk Galaxies
• EC-SNe from super-AGB progenitors: theoretical models vs. observations
• Lessons from the Onset of a Common Envelope Episode: the Remarkable M31 2015 Luminous Red Nova Outburst
• Massive stars exploding in a He-rich circumstellar medium. II. The transitional case of SN 2005la
• Massive-Star Mergers and the Recent Transient in NGC4490: A More Massive Cousin of V838 Mon and V1309 Sco
• Pre-explosion spiral mass loss of a binary star merger
• Short-Lived Circumstellar Interaction in the Low-Luminosity Type IIP SN 2016bkv
• Evolution of V838 Monocerotis during and after the 2002 eruption
• A very faint core-collapse supernova in M85
• Violent Stellar Merger Model for Transient Events
• Massive stars exploding in a He-rich circumstellar medium. IV. Transitional Type Ibn Supernovae
• Electron-capture supernovae exploding within their progenitor wind
• SN 2011hw: Helium-Rich Circumstellar Gas and the Luminous Blue Variable to Wolf-Rayet Transition in Supernova Progenitors
• Submillimeter-wave emission of three Galactic red novae: cool molecular outflows produced by stellar mergers
• Almost Gone: SN~2008S and NGC~300 2008OT-1 are Fainter than their Progenitors
• A Spitzer/IRS Spectrum of the 2008 Luminous Transient in NGC 300: Connection to Proto-Planetary Nebulae
• A Luminous Red Nova in M31 and its Progenitor System
• Spitzer Observations of the New Luminous Red Nova M85OT2006-1
• Supernova Impostors and other Gap Transients
• The Dusty Aftermath of the V1309 Sco Binary Merger
• On the triple peaks of SNHunt248 in NGC 5806
• Keck/HIRES spectroscopy of V838 Monocerotis in October 2005
• Electron Capture Supernovae of Super-AGB Stars: Sensitivity on Input Physics
• ASTRONIRCAM - infrared camera-spectrograph for Sternberg institute 2.5 METER TELESCOPE
• Hoki: Making BPASS accessible through Python
• The transitional gap transient AT 2018hso: new insights on the luminous red nova phenomenon
• SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant
• The Cold and Dusty Circumstellar Matter around Fast-expanding Type Ia Supernovae
• MASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31: Discovery, Light Curve, Hydrodynamics, Evolution
• Luminous Red Nova AT 2019zhd, a new merger in M 31
• An Extended Grid of Nova Models. III. Very Luminous, Red Novae
• A Closer Look at the Fluctuations in Brightness of SN 2009ip During Its Late 2012 Eruption
• A blind HI survey in the Ursa Major region
• Efficiently jet-powered radiation in intermediate-luminosity optical transients (ILOTS)
• The Evolution of Luminous Red Nova AT 2017jfs in NGC 4470
• Explaining Two Recent Intermediate Luminosity Optical Transients (ILOTs) by a Binary Interaction and Jets
• Low luminosity Type II supernovae -- IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class
• The dusty aftermath of SN Hunt248: merger-burst remnant?
• The luminous red nova variety: AT 2020hat and AT 2020kog
• Luminous Red Nova 2015 in the Galaxy M101
• Low luminosity Type II supernovae III. SN 2018hwm, a faint event with an unusually long plateau
• Origin of Dust around V1309 Sco
• The Carnegie Supernova Project II. Observations of the intermediate luminosity red transient SNhunt120
• The low-luminosity type II SN\,2016aqf: A well-monitored spectral evolution of the Ni/Fe abundance ratio
• The Carnegie Supernova Project II. Observations of the luminous red nova AT 2014ej
• Preparing to discover the unknown with Rubin LSST -- I: Time domain
• Gap Transients Interacting with Circumstellar Medium
• Anisotropies of Cosmic Optical and Near-IR Background from China Space Station Telescope (CSST)
• Polarimetric evolution of V838 Mon
• Calibrating photometric redshift measurements with the Multi-channel Imager (MCI) of the China Space Station Telescope (CSST)
• SiO maser astrometry of the red transient V838 Monocerotis
• Intermediate Luminosity Optical Transients (ILOTs) from merging giants
• The mid-infrared environment of the stellar merger remnant V838 Monocerotis
• Going Forward with the Nancy Grace Roman Space Telescope Transient Survey: Validation of Precision Forward-Modeling Photometry for Undersampled Imaging
• The circumstellar matter of type II intermediate luminosity optical transients (ILOTs)

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