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The Ultraviolet-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event

Chornock, R. and Martin, D. C. and Neill, J. D. (2014) The Ultraviolet-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event. Astrophysical Journal, 780 (1). Art. No. 44. ISSN 0004-637X.

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We present the Pan-STARRS1 discovery of the long-lived and blue transient PS1-11af, which was also detected by Galaxy Evolution Explorer with coordinated observations in the near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an early type galaxy at redshift z = 0.4046 that exhibits no evidence for star formation or active galactic nucleus activity. Four epochs of spectroscopy reveal a pair of transient broad absorption features in the UV on otherwise featureless spectra. Despite the superficial similarity of these features to P-Cygni absorptions of supernovae (SNe), we conclude that PS1-11af is not consistent with the properties of known types of SNe. Blackbody fits to the spectral energy distribution are inconsistent with the cooling, expanding ejecta of a SN, and the velocities of the absorption features are too high to represent material in homologous expansion near a SN photosphere. However, the constant blue colors and slow evolution of the luminosity are similar to previous optically selected tidal disruption events (TDEs). The shape of the optical light curve is consistent with models for TDEs, but the minimum accreted mass necessary to power the observed luminosity is only ~0.002 M ☉, which points to a partial disruption model. A full disruption model predicts higher bolometric luminosities, which would require most of the radiation to be emitted in a separate component at high energies where we lack observations. In addition, the observed temperature is lower than that predicted by pure accretion disk models for TDEs and requires reprocessing to a constant, lower temperature. Three deep non-detections in the radio with the Very Large Array over the first two years after the event set strict limits on the production of any relativistic outflow comparable to Swift J1644+57, even if off-axis.

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Neill, J. D.0000-0002-0466-1119
Alternate Title:The UV-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event
Additional Information:© 2014 American Astronomical Society. Received 2013 September 11; accepted 2013 November 9; published 2013 December 11. We thank the staffs at PS1, Magellan, Gemini, the MMT, and the VLA for their assistance with scheduling and performing these observations. We acknowledge useful discussions with E. Ramirez-Ruiz, the assistance of T. Laskar with some of the MMT observations, and the help of A. Monson with FourStar data reduction. B.A.Z. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302954. This paper includes data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, Chile. Some observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. The Pan-STARRS1 Surveys (PS1) have been made possible through the contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and theMax Planck Institute for Extraterrestrial Physics, Garching, the Johns Hopkins University, Durham University, the University of Edinburgh, Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under grant No. AST-1238877, and the University of Maryland. Some observations were obtained under Program ID GS-2011A-Q-29 (PI: Berger) at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovaciόn Productiva (Argentina). S.J.S. acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement No. 291222. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. R.P.K.’s work on SNe is supported in part by NSF grant AST-1211196. Partial support for this work was also provided by NSF grant AST-1009749 to J.T.. STSDAS is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. Development of the BOXFIT code was supported in part by NASA through grant NNX10AF62G issued through the Astrophysics Theory Program and by the NSF through grant AST-1009863. Some of the computations in this paper were run on the Odyssey cluster supported by the FAS Science Division Research Computing Group at Harvard University. Facilities: PS1 (GPC1),Magellan:Baade (IMACS, FourStar), Magellan:Clay (LDSS3), MMT (Blue Channel spectrograph), Gemini:South (GMOS-S), EVLA
Group:Space Astrophysics Laboratory
Funding AgencyGrant Number
NSF Astronomy and Astrophysics Postdoctoral FellowshipAST-1302954
European Research Council (ERC)291222
Harvard UniversityUNSPECIFIED
Subject Keywords:accretion, accretion disks; black hole physics; galaxies: nuclei
Record Number:CaltechAUTHORS:20140130-140916310
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Official Citation:The Ultraviolet-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event R. Chornock et al. 2014 ApJ 780 44
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43589
Deposited By: Ruth Sustaita
Deposited On:30 Jan 2014 22:55
Last Modified:22 May 2017 23:13

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