| Source: |
Pan-Starrs, Asas-Sn, Atlas, Holoien, T W S, Huber, M E, Shappee, B J, Eracleous, M, Auchettl, K, Tucker, M A, Chambers, K C, Kochanek, C S, Stanek, K Z, Rest, A, Bersier, D, Post, R S, Aldering, G, Ponder, K A, Simon, J D, Kankare, E, Dong, D, Hallinan, G, Reddy, N A, Sanders, R L, Bulger, J, Lowe, T B, Magnier, E A, Schultz, A S B, Waters, C Z, Willman, M, Wright, D, Young, D R, Dong, S, Prieto, J L, Thompson, T A, Denneau, L, Flewelling, H, Heinze, A N, Smartt, S J, Stalder, B, Tonry, .... |
| Description: |
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 × 10 43 erg s -1 . PS18kh radiated E = (3.45 ± 0.22) × 10 50 erg over the period of observation, with (1.42 ± 0.20) × 10 50 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. |