Journal
ASTROPHYSICAL JOURNAL
Volume 873, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/ab04b0
Keywords
accretion, accretion disks; black hole physics; galaxies: nuclei; stars: individual (iPTF15af)
Categories
Funding
- GROWTH project - National Science Foundation (NSF) [AST1545949]
- Netherlands Organisation for Scientific Research (NWO) [016.192.277]
- NASA [PF6-170148, NAS5-98034]
- I-Core Program of the Planning and Budgeting Committee
- Israel Science Foundation
- GIF, the German-Israeli Foundation for Scientific Research and Development
- TABASGO Foundation
- Christopher R. Redlich Fund
- Miller Institute for Basic Research in Science (UC Berkeley)
- W. M. Keck Foundation
- NASA
- NSF
- STFC [ST/P000495/1] Funding Source: UKRI
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We present multiwavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by the intermediate Palomar Transient Factory survey at redshift z = 0.07897. The optical and ultraviolet (UV) light curves of the transient show a slow decay over 5 months, in agreement with previous optically discovered TDEs. It also has a comparable blackbody peak luminosity of L-peak approximate to 1.5 x 10(44) erg s(-1). The inferred temperature from the optical and UV data shows a value of (3-5) x 10(4) K. The transient is not detected in X-rays up to L-X < 3 x 10(42) erg s(-1) within the first 5 months after discovery. The optical spectra exhibit two distinct broad emission lines in the He II region, and at later times also H alpha emission. Additionally, emission from [N III] and [O III] is detected, likely produced by the Bowen fluorescence effect. UV spectra reveal broad emission and absorption lines associated with high-ionization states of N V, C IV, Si IV, and possibly P V. These features, analogous to those of broad absorption line quasars (BAL QSOs), require an absorber with column densities N-H > 10(23) cm(-2). This optically thick gas would also explain the nondetection in soft X-rays. The profile of the absorption lines with the highest column density material at the largest velocity is opposite that of BAL QSOs. We suggest that radiation pressure generated by the TDE flare at early times could have provided the initial acceleration mechanism for this gas. Spectral UV line monitoring of future TDEs could test this proposal.
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