The Tidal Disruption Event AT 2018hyz II: Light Curve Modeling of a Partially Disrupted Star. (arXiv:2003.05469v2 [astro-ph.HE] UPDATED)

The Tidal Disruption Event AT 2018hyz II: Light Curve Modeling of a Partially Disrupted Star. (arXiv:2003.05469v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Gomez_S/0/1/0/all/0/1">Sebastian Gomez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nicholl_M/0/1/0/all/0/1">Matt Nicholl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Short_P/0/1/0/all/0/1">Philip Short</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Margutti_R/0/1/0/all/0/1">Raffaella Margutti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alexander_K/0/1/0/all/0/1">Kate D. Alexander</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blanchard_P/0/1/0/all/0/1">Peter K. Blanchard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berger_E/0/1/0/all/0/1">Edo Berger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eftekhari_T/0/1/0/all/0/1">Tarraneh Eftekhari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schulze_S/0/1/0/all/0/1">Steve Schulze</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Anderson_J/0/1/0/all/0/1">Joseph Anderson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arcavi_I/0/1/0/all/0/1">Iair Arcavi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chornock_R/0/1/0/all/0/1">Ryan Chornock</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cowperthwaite_P/0/1/0/all/0/1">Philip S. Cowperthwaite</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Galbany_L/0/1/0/all/0/1">Lluís Galbany</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Herzog_L/0/1/0/all/0/1">Laura J. Herzog</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hiramatsu_D/0/1/0/all/0/1">Daichi Hiramatsu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hosseinzadeh_G/0/1/0/all/0/1">Griffin Hosseinzadeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Laskar_T/0/1/0/all/0/1">Tanmoy Laskar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bravo_T/0/1/0/all/0/1">Tomás E. Müller Bravo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Patton_L/0/1/0/all/0/1">Locke Patton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Terreran_G/0/1/0/all/0/1">Giacomo Terreran</a>

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 $E = 9times10^{50}$ 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 $sim
4times10^{-14}$ 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 $5.2times10^6$
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).

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