The Tidal Disruption Event AT 2018hyz II: Light Curve Modeling of a Partially Disrupted Star

Abstract

AT 2018hyz (=ASASSN-18zj) is a tidal disruption event (TDE) located in the nucleus of a quiescent E+A galaxy at a redshift of $z=0.04573$, first detected by the All-Sky Automated Survey for Supernovae (ASAS-SN). We present optical+UV photometry of the transient, as well as an X-ray spectrum and radio upper limits. The bolometric light curve of AT 2018hyz is comparable to other known TDEs and declines at a rate consistent with a $t^{-5/3}$ at early times, emitting a total radiated energy of $E=9\times 10^{50}$ erg. An excess bump appears in the UV light curve about 50 days after bolometric peak, followed by a flattening beyond 250 days. The light curve shows an excess bump in the UV about 50 days after bolometric peak lasting for at least 100 days, which may be related to an outflow. We detect a constant X-ray source present for at least 86 days. The X-ray spectrum shows a total unabsorbed flux of $\sim 4\times 10^{-14}$ erg cm${}^{-2}$ s${}^{-1}$ and is best fit by a blackbody plus power-law model with a photon index of $\Gamma =0.8$. A thermal X-ray model is unable to account for photons $>1$ keV, while the radio non-detection favors inverse-Compton scattering rather than a jet for the non-thermal component. We model the optical and UV light curves using the Modular Open-Source Fitter for Transients (MOSFiT) and find a best fit for a black hole of $5.2\times 10^6$ M${}_{\odot }$ partially disrupting a $0.1$ M${}_{\odot }$ star (stripping a mass of $\sim 0.01$ M${}_{\odot }$ for the inferred impact parameter, $\beta =0.6$). The low optical depth implied by the small debris mass may explain how we are able to see hydrogen emission with disk-like line profiles in the spectra of AT 2018hyz (see our companion paper, Short et al.~2020).

10 pages, 10 figures, published in MNRAS

References in corpus (10)

• The Gaia mission
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core
• A Continuum of H- to He-Rich Tidal Disruption Candidates With a Preference for E+A Galaxies
• The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole
• X-ray Brightening and UV Fading of Tidal Disruption Event ASASSN-15oi
• Tidal disruptions of main sequence stars -- III. Stellar mass dependence of the character of partial disruptions
• The Tidal Disruption Event AT 2018hyz I: Double-peaked emission lines and a flat Balmer decrement
• Constraints on off-axis jets from stellar tidal disruption flares
• The Long Term Evolution of ASASSN-14li

Cited by in corpus (32)

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• The Tidal Disruption Event AT 2018hyz I: Double-peaked emission lines and a flat Balmer decrement
• Double-Peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event
• Systematic light curve modelling of TDEs: statistical differences between the spectroscopic classes
• Fallback Rates from Partial Tidal Disruption Events
• The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654
• An elliptical accretion disk following the tidal disruption event AT 2020zso
• Generalized equipartition method from an arbitrary viewing angle
• A Swift Fix for Nuclear Outbursts
• The Luminosity Function of Tidal Disruption Flares for the ZTF-I Survey
• Identifying Tidal Disruption Events with an Expansion of the FLEET Machine Learning Algorithm
• Light Curves of Partial Tidal Disruption Events
• Interaction of an outflow with surrounding gaseous clouds as the origin of the late-time radio flares in TDEs
• Elliptical accretion disk as a model for tidal disruption events
• Revisit the rate of tidal disruption events: the role of the partial tidal disruption event
• Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy
• The fast transient AT 2023clx in the nearby LINER galaxy NGC 3799 as a tidal disruption of a very low-mass star
• Scary Barbie: An Extremely Energetic, Long-Duration Tidal Disruption Event Candidate Without a Detected Host Galaxy at z = 0.995
• Fate of the remnant in tidal stripping event: repeating and non-repeating
• Exploring the origin of stars on bound and unbound orbits causing tidal disruption events
• Characterisation of the X-ray point source variability in the eROSITA south ecliptic pole field
• Partial Tidal Disruption Events by Intermediate-mass Black Holes in Supermassive and Intermediate-mass Black Hole Binaries
• Propagation of Precessing Jet in Envelope of Tidal Disruption Events
• MUSE IFU observations of galaxies hosting Tidal Disruption Events
• Accretion Flares from Stellar Collisions in Galactic Nuclei
• Revisiting the unification of tidal disruption events with polarimetry
• A detailed spectroscopic study of Tidal Disruption Events
• TUVO-21acq: a new cataclysmic variable discovered through a UV outburst
• Early results in the search for extreme coronal line emitters with the Dark Energy Spectroscopic Instrument
• A Mildly Relativistic Outflow Launched Two Years after Disruption in the Tidal Disruption Event AT2018hyz