Panchromatic evolution of three luminous red novae: Forbidden hugs in pandemic times -- IV

Abstract

We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe): AT2018bwo, AT2021afy, and AT2021blu. AT2018bwo was discovered in NGC45 (at 6.8 Mpc) a few weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 10^40 erg/s. AT2021afy, hosted by UGC10043 (49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(+-0.6)x10^41 erg/s. For AT2021blu in UGC5829, (8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of AT2021blu was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of AT2021blu shows a double peak, with a prominent early maximum reaching a luminosity of 6.5x10^40 erg/s, which is half of that of AT2021afy. The spectra of AT2021afy and AT2021blu display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of AT2018bwo are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak, AT2018bwo was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from 13Mo for AT2018bwo, to 13-18Mo for AT2021blu, and over 40Mo for AT2021afy.

arXiv comment33 pages, 19 figures, 7 tables (plus 3 available at the CDS). Accepted for publication in A&A

References in corpus (81)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Binary interaction dominates the evolution of massive stars
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The Swift Ultra-Violet/Optical Telescope
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• ATLAS: A High-Cadence All-Sky Survey System
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Common Envelope Evolution: Where we stand and how we can move forward
• The Pan-STARRS1 Photometric System
• WFPC2 Stellar Photometry with HSTphot
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• The Zwicky Transient Facility: Science Objectives
• WISeREP - An Interactive Supernova Data Repository
• The SDSS View of the Palomar-Green Bright Quasar Survey
• The Pan-STARRS1 Database and Data Products
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Reevaluating Old Stellar Populations
• The HST Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
• Cosmicflows-3
• V1309 Scorpii: merger of a contact binary
• Design and operation of the ATLAS Transient Science Server
• Pan-STARRS Photometric and Astrometric Calibration
• Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova 2006X in M100
• Identification of the Long-Sought Common-Envelope Events
• Eruptions of the V838 Mon type: stellar merger versus nuclear outburst models
• Stellar Mergers Are Common
• 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?
• The early detection and follow-up of the highly obscured Type II supernova 2016ija/DLT16am
• Optical and Infrared Colors of Stars Observed by 2MASS and SDSS
• 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
• Lessons from the Onset of a Common Envelope Episode: the Remarkable M31 2015 Luminous Red Nova Outburst
• OGLE-2002-BLG-360: from a gravitational microlensing candidate to an overlooked red transient
• Massive-Star Mergers and the Recent Transient in NGC4490: A More Massive Cousin of V838 Mon and V1309 Sco
• The resolved stellar populations in the LEGUS galaxies
• Pre-explosion spiral mass loss of a binary star merger
• Carnegie Supernova Project-II: The Near-infrared Spectroscopy Program
• Runaway Coalescence at the Onset of Common Envelope Episodes
• ZZ Piscis Austrinus (ZZ PsA): A bright red nova progenitor and the instability mass ratio of contact binary stars
• Burying a Binary: Dynamical Mass Loss and a Continuous Optically-Thick Outflow Explain the Candidate Stellar Merger V1309 Scorpii
• Luminous Red Novae: population models and future prospects
• A Luminous Red Nova in M31 and its Progenitor System
• Alert Classification for the ALeRCE Broker System: The Real-time Stamp Classifier
• Supernova Impostors and other Gap Transients
• On the triple peaks of SNHunt248 in NGC 5806
• Pre-Common-Envelope Mass Loss from Coalescing Binary Systems
• The transitional gap transient AT 2018hso: new insights on the luminous red nova phenomenon
• Light Curve Model for Luminous Red Novae and Inferences about the Ejecta of Stellar Mergers
• SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant
• Progenitor, Precursor and Evolution of the Dusty Remnant of the Stellar Merger M31-LRN-2015
• MASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31: Discovery, Light Curve, Hydrodynamics, Evolution
• Operation of the jet feedback mechanism (JFM) in intermediate luminosity optical transients (ILOTs)
• Luminous Red Nova AT 2019zhd, a new merger in M 31
• The January 2015 outburst of a red nova in M31
• An Extended Grid of Nova Models. III. Very Luminous, Red Novae
• Efficiently jet-powered radiation in intermediate-luminosity optical transients (ILOTS)
• Intermediate luminosity optical transients during the grazing envelope evolution (GEE)
• 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
• Characterisation of Sloan Digital Sky Survey Stellar Photometry
• 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
• VLT/UVES spectroscopy of V4332 Sagittarii in 2005: The best view on a decade-old stellar-merger remnant
• Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631
• V4332 Sgr in 'Quiescence'
• Imaging of star clusters in unperturbed spiral galaxies with the Advanced Camera for Surveys. I. The low luminosity galaxy NGC 45
• The Carnegie Supernova Project II. Observations of the luminous red nova AT 2014ej
• Observational Constraints on the Common Envelope Phase
• Gap Transients Interacting with Circumstellar Medium
• Explaining recently studied intermediate luminosity optical transients (ILOTs) with jet powering
• Infrared spectroscopy of CK Vulpeculae: revealing a remarkably powerful blast from the past
• Revisiting V1309 Sco 2008 outburst spectra. Observational evidence for theoretical modeling of stellar mergers
• Optical Rebrightening of Extragalactic Transients from the Zwicky Transient Facility

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• YSE-PZ: A Transient Survey Management Platform that Empowers the Human-in-the-Loop
• Two-Dimensional Radiation-Hydrodynamic Simulations of Luminous Red Novae
• A study in scarlet -- II. Spectroscopic properties of a sample of Intermediate Luminosity Red Transients
• From Common Envelope Evolution to Luminous Red Novae I: A One-dimensional Radiation Hydrodynamic Model
• Hertzsprung gap stars in nearby galaxies and the Quest for Luminous Red Novae Progenitors
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