The Broad Absorption Line Tidal Disruption Event iPTF15af: Optical and Ultraviolet Evolution

Journal Article · Fri Mar 01 00:00:00 EST 2019 · The Astrophysical Journal (Online)

DOI:https://doi.org/10.3847/1538-4357/ab04b0· OSTI ID:1526587

Blagorodnova, N.  ^[1]; Cenko, S. B.  ^[2]; Kulkarni, S. R.  ^[3]; Arcavi, I.  ^[4]; Bloom, J. S. ^[5]; Duggan, G.  ^[3]; Filippenko, A. V.  ^[5]; Fremling, C.  ^[3]; Horesh, A. ^[6]; Hosseinzadeh, G.  ^[7]; Karamehmetoglu, E.  ^[8]; Levan, A.  ^[9]; Masci, F. J.  ^[3]; Nugent, P. E.  ^[10]; Pasham, D. R. ^[11]; Veilleux, S.  ^[12]; Walters, R. ^[3]; Yan, L. ^[3]; Zheng, W. ^[5]

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1. California Inst. of Technology (CalTech), Pasadena, CA (United States); Radboud Univ., Nijmegen (The Netherlands)
2. Univ. of Maryland, College Park, MD (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
3. California Inst. of Technology (CalTech), Pasadena, CA (United States)
4. Univ. of California, Santa Barbara, CA (United States); Las Cumbres Observatory, Goleta, CA (United States); Univ. of California, Berkeley, CA (United States)
5. Univ. of California, Berkeley, CA (United States)
6. The Hebrew Univ. of Jerusalem, Jerusalem (Israel)
7. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
8. Stockholm Univ., Stockholm (Sweden)
9. Univ. of Warwick, Coventry (United Kingdom)
10. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
11. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
12. Univ. of Maryland, College Park, MD (United States)

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 $${L}_{\mathrm{peak}}\approx 1.5\times {10}^{44}$$ $$\mathrm{erg}\,{{\rm{s}}}^{-1}$$. The inferred temperature from the optical and UV data shows a value of (3–5) × 104 K. The transient is not detected in X-rays up to $${L}_{{\rm{X}}}\lt 3\times {10}^{42}$$ $$\mathrm{erg}\,{{\rm{s}}}^{-1}$$ 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 Hα 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 $${N}_{{\rm{H}}}\gt {10}^{23}$$ cm^–2. Here, 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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1526587
• Journal Information: The Astrophysical Journal (Online), Vol. 873, Issue 1; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
accretion
accretion disks
black hole physics
galaxies: nuclei
stars: individual (iPTF15af)