The Eruption of the Candidate Young Star ASASSN-15qi

Abstract

Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The $\sim 3.5$ mag brightening in the $V$ band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1 mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from $\sim 10,000$ K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000 km/s. The wind and hot gas both disappeared as the outburst faded and the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H${}_2$ is detected in emission from vibrational levels as high as $v=11$, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, although the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling.

arXiv comment23 pages; accepted by ApJ

References in corpus (49)

• The USNO-B Catalog
• 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
• Las Cumbres Observatory Global Telescope Network
• Astrometry.net: Blind astrometric calibration of arbitrary astronomical images
• Photometric Calibration of the Swift Ultraviolet/Optical Telescope
• CSI 2264: Simultaneous optical and infrared light curves of young disk-bearing stars in NGC 2264 with CoRoT and Spitzer-- evidence for multiple origins of variability
• X-Shooter spectroscopy of young stellar objects: IV -- Accretion in low-mass stars and sub-stellar objects in Lupus
• Episodic accretion in magnetically layered protoplanetary discs
• The Origin of Episodic Accretion Bursts in the Early Stages of Star Formation
• Point Source Extraction with MOPEX
• Non-steady Accretion in Protostars
• Episodic Accretion on to Strongly Magnetic Stars
• Studies of Diffuse Interstellar Bands. V. Pairwise Correlations of Eight Strong DIBs and Neutral Hydrogen, Molecular Hydrogen, and Color Excess
• Accretion Discs Trapped Near Corotation
• The Second Data Release of the INT Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS DR2)
• Direct magnetic field detection in the innermost regions of an accretion disc
• A combined optical/infrared spectral diagnostic analysis of the HH1 jet
• Accretion Outbursts in Self-gravitating Protoplanetary Disks
• Investigating the Near-Infrared Properties of Planetary Nebula II. Medium Resolution Spectra
• Trigonometric Parallaxes of Star Forming Regions in the Perseus Spiral Arm
• Modeling T Tauri Winds from He I 10830 Profiles
• Multidimensional models of hydrogen and helium emission line profiles for classical T Tauri Stars: method, tests and examples
• Evidence for an FU Orionis-like Outburst from a Classical T Tauri Star
• Origins of the H, He I, and Ca II Line Emission in Classical T Tauri Stars
• The 2008 extreme outburst of the young eruptive variable star Ex Lupi
• Near Infrared Spectroscopic Monitoring of EXor variables: First Results
• Redshifted Absorption at He I 10830 as a Probe of the Accretion Geometry of T Tauri Stars
• On the nature of the EXor accretion events: an unfrequent manifestation of a common phenomenology ?
• Diagnosing Mass Flows Around Herbig Ae/Be Stars Using the He I 10830 Line
• A Spectroscopic and Photometric Survey of Novae in M31
• The JCMT Gould Belt Survey: A Quantitative Comparison Between SCUBA-2 Data Reduction Methods
• Unveiling extremely veiled T Tauri stars
• Long-wavelength excesses of FU Orionis objects: flared outer disks or infalling envelopes?
• High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars
• Spitzer Imaging of the Nearby Rich Young Cluster, Cep OB3b
• Discovery and Observations of ASASSN-13db, an EX Lupi-Type Accretion Event on a Low-Mass T Tauri Star
• Near-infrared spectroscopy of EX Lupi in outburst
• Optical Mass Flow Diagnostics in Herbig Ae/Be Stars
• V899 Mon: An Outbursting Protostar With Peculiar Light Curve And Its Transition Phases
• Depletion of molecular gas by an accretion outburst in a protoplanetary disk
• The nature of the recent extreme outburst of the Herbig Be/FU Ori binary Z CMa
• V2492 Cygni: The Early Evolution of the 2010 Outburst
• LBT/LUCIFER near-infrared spectroscopy of PV Cephei. An outbursting young stellar object with an asymmetric jet
• High Resolution Infrared Imaging & Spectroscopy of the Z Canis Majoris System During Quiescence & Outburst
• Study of Molecular Clouds associated with HII Regions
• Dimming and CO absorption toward the AA Tau protoplanetary disk: An infalling flow caused by disk instability?
• Cold Dust in Hot Regions
• Episodic High Velocity Outflows from V899 Mon: A Constraint On The Outflow Mechanisms

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• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• A Near-IR Spectroscopic Survey of FU Orionis Objects
• The ASAS-SN Bright Supernova Catalog -- III. 2016
• The largest M dwarfs flares from ASAS-SN
• The ASAS-SN Bright Supernova Catalog -- IV. 2017
• The Relative Specific Type Ia Supernovae Rate From Three Years of ASAS-SN
• The 2014-2017 outburst of the young star ASASSN-13db: A time-resolved picture of a very low-mass star between EXors and FUors
• PTF 14jg: The Remarkable Outburst and Post-Burst Evolution of a Previously Anonymous Galactic Star
• An intermediate-luminosity-optical-transient (ILOT) model for the young stellar object ASASSN-15qi
• Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands
• V899 Mon: a peculiar eruptive young star close to the end of its outburst
• Gaia21bty: An EXor lightcurve exhibiting an FUor spectrum
• On the nature of the planet-powered transient event ZTF SLRN-2020
• Towards a better classification of unclear eruptive variables: the cases of V2492 Cyg, V350 Cep, and ASASSN-15qi
• Gaia20bdk -- a new FUor in Sh 2-301 Star Forming Region
• Evolution of the ZTF SLRN-2020 star-planet merger