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Open Access Publications from the University of California

PS18kh: A New Tidal Disruption Event with a Non-axisymmetric Accretion Disk

  • Author(s): Pan-Starrs
  • Asas-Sn
  • Atlas
  • Holoien, TWS
  • Huber, ME
  • Shappee, BJ
  • Eracleous, M
  • Auchettl, K
  • Brown, JS
  • Tucker, MA
  • Chambers, KC
  • Kochanek, CS
  • Stanek, KZ
  • Rest, A
  • Bersier, D
  • Post, RS
  • Aldering, G
  • Ponder, KA
  • Simon, JD
  • Kankare, E
  • Dong, D
  • Hallinan, G
  • Reddy, NA
  • Sanders, RL
  • Topping, MW
  • Bulger, J
  • Lowe, TB
  • Magnier, EA
  • Schultz, ASB
  • Waters, CZ
  • Willman, M
  • Wright, D
  • Young, DR
  • Dong, S
  • Prieto, JL
  • Thompson, TA
  • Denneau, L
  • Flewelling, H
  • Heinze, AN
  • Smartt, SJ
  • Smith, KW
  • Stalder, B
  • Tonry, JL
  • Weiland, H
  • et al.

© 2019. The American Astronomical Society. All rights reserved.. We present the discovery of PS18kh, a tidal disruption event discovered at the center of SDSS J075654.53+341543.6 (d ≃ 322 Mpc) by the Pan-STARRS Survey for Transients. Our data set includes pre-discovery survey data from Pan-STARRS, the All-sky Automated Survey for Supernovae, and the Asteroid Terrestrial-impact Last Alert System as well as high-cadence, multiwavelength follow-up data from ground-based telescopes and Swift, spanning from 56 days before peak light until 75 days after. The optical/UV emission from PS18kh is well-fit as a blackbody with temperatures ranging from T ≃ 12,000 K to T ≃ 25,000 K and it peaked at a luminosity of L ≃ 8.8 × 1043 erg s-1. PS18kh radiated E = (3.45 ± 0.22) × 1050 erg over the period of observation, with (1.42 ± 0.20) × 1050 erg being released during the rise to peak. Spectra of PS18kh show a changing, boxy/double-peaked Hα emission feature, which becomes more prominent over time. We use models of non-axisymmetric accretion disks to describe the profile of the Hα line and its evolution. We find that at early times the high accretion rate leads the disk to emit a wind which modifies the shape of the line profile and makes it bell-shaped. At late times, the wind becomes optically thin, allowing the non-axisymmetric perturbations to show up in the line profile. The line-emitting portion of the disk extends from r in ∼ 60r g to an outer radius of r out ∼ 1400r g and the perturbations can be represented either as an eccentricity in the outer rings of the disk or as a spiral arm in the inner disk.

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