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

Blagorodnova, N. and Cenko, S. B. and Kulkarni, S. R. and Arcavi, I. and Bloom, J. S. and Duggan, G. and Filippenko, A. V. and Fremling, C. and Horesh, A. and Hosseinzadeh, G. and Karamehmetoglu, E. and Levan, A. and Masci, F. J. and Nugent, P. E. and Pasham, D. R. and Veilleux, S. and Walters, R. and Yan, L. and Zheng, W. (2019) The Broad Absorption Line Tidal Disruption Event iPTF15af: Optical and Ultraviolet Evolution. Astrophysical Journal, 873 (1). Art. No. 92. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20190307-092619351

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Abstract

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) ≈ 1.2 × 10^(44) erg s^(-1). The inferred temperature from the optical and UV data shows a value of (3–5) × 10^4 K. The transient is not detected in X-rays up to L_X < 3 × 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 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_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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab04b0DOIArticle
https://arxiv.org/abs/1809.07446arXivDiscussion Paper
ORCID:
AuthorORCID
Blagorodnova, N.0000-0003-0901-1606
Cenko, S. B.0000-0003-1673-970X
Kulkarni, S. R.0000-0001-5390-8563
Arcavi, I.0000-0001-7090-4898
Bloom, J. S.0000-0002-7777-216X
Duggan, G.0000-0002-9256-6735
Filippenko, A. V.0000-0003-3460-0103
Fremling, C.0000-0002-4223-103X
Horesh, A.0000-0002-5936-1156
Hosseinzadeh, G.0000-0002-0832-2974
Karamehmetoglu, E.0000-0001-6209-838X
Levan, A.0000-0001-7821-9369
Masci, F. J.0000-0002-8532-9395
Nugent, P. E.0000-0002-3389-0586
Veilleux, S.0000-0002-3158-6820
Walters, R.0000-0002-1835-6078
Yan, L.0000-0003-1710-9339
Additional Information:© 2019. The American Astronomical Society. Received 2018 September 19; revised 2019 January 23; accepted 2019 February 1; published 2019 March 7. We thank the anonymous referee, whose comments and suggestions helped to improve the paper. We are grateful to Peter Maksym, Sterl Phinney, Eliot Quataert, Clément Bonnerot, Tiara Hung, and Sjoert Van Velzen for valuable discussions and comments on this work. We are grateful to Eric Bellm, Melissa Graham, Anna Ho, and Daniel Perley for carrying out some of the spectroscopic observations and/or reductions, and Linda Strubbe for her support with the HST proposal. We thank the HST staff for the prompt scheduling of these ToO observations, as well as the PI Neil Gehrels and the Swift ToO team for the timely execution of our observations. This work was supported by the GROWTH project funded by the National Science Foundation (NSF) under grant AST-1545949. This work is part of the research program VENI, with project no. 016.192.277, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). Support for I.A. was provided by NASA through the Einstein Fellowship Program, grant PF6-170148. A.H. acknowledges support by the I-Core Program of the Planning and Budgeting Committee and the Israel Science Foundation. This research was supported by a Grant from the GIF, the German-Israeli Foundation for Scientific Research and Development. A.V.F.'s group at UC Berkeley is grateful for financial assistance from the TABASGO Foundation, the Christopher R. Redlich Fund, and the Miller Institute for Basic Research in Science (UC Berkeley). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA); the observatory was made possible by the generous financial support of the W. M. Keck Foundation. This work makes use of observations from Las Cumbres Observatory. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the NSF. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by NASA. Based on observations made with the NASA Galaxy Evolution Explorer. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. Facilities: HST (STIS) - , Karl G. Jansky Very Large Array - , Keck:I (LRIS) - , PO:1.2 m - , PO:1.5 m - , Swift - , WISE. - Software: Astropy (The Astropy Collaboration et al. 2018), emcee (Foreman-Mackey et al. 2013), FPipe (Fremling et al. 2016), lcogtsnpipe (Valenti et al. 2016), lmfit (Newville et al. 2014), lpipe http://www.astro.caltech.edu/~dperley/programs/lpipe.html, MOSFIT (Guillochon et al. 2018), NumPy (van der Walt et al. 2011), PTFIDE (Masci et al. 2017), SciPy (Jones et al. 2001).
Group:Infrared Processing and Analysis Center (IPAC), Palomar Transient Factory
Funders:
Funding AgencyGrant Number
NSFAST-1545949
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)016.192.277
NASA Einstein FellowshipPF6-170148
I-CORE Program of the Planning and Budgeting CommitteeUNSPECIFIED
Israel Science FoundationUNSPECIFIED
German-Israeli Foundation for Research and DevelopmentUNSPECIFIED
TABASGO FoundationUNSPECIFIED
Christopher R. Redlich FundUNSPECIFIED
Miller Institute for Basic Research in ScienceUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
NASA/JPL/CaltechUNSPECIFIED
NASANAS5-98034
Subject Keywords:accretion, accretion disks; black hole physics; galaxies: nuclei; stars: individual (iPTF15af)
Issue or Number:1
Record Number:CaltechAUTHORS:20190307-092619351
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190307-092619351
Official Citation:N. Blagorodnova et al 2019 ApJ 873 92
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93621
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:08 Mar 2019 15:40
Last Modified:21 Nov 2019 23:33

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