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Rapid “Turn-on” of Type-1 AGN in a Quiescent Early-type Galaxy SDSS1115+0544

Yan, Lin and Wang, Tinggui and Jiang, Ning and Stern, Daniel and Dou, Liming and Fremling, C. and Graham, M. J. and Drake, A. J. and Yang, Chenwei and Burdge, K. and Kasliwal, M. M. (2019) Rapid “Turn-on” of Type-1 AGN in a Quiescent Early-type Galaxy SDSS1115+0544. Astrophysical Journal, 874 (1). Art. No. 44. ISSN 1538-4357.

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We present a detailed study of a transient in the center of SDSS1115+0544 based on the extensive UV, optical, mid-IR light curves (LCs) and spectra over 1200 days. The host galaxy is a quiescent early-type galaxy at z = 0.0899 with a black hole mass of 2 × 10^7 M⊙. The transient underwent a 2.5 mag brightening over ~120 days, reaching a peak V-band luminosity (extinction corrected) of −20.9 mag, then fading 0.5 mag over 200 days, settling into a plateau of >600 days. Following the optical brightening are the significant mid-IR flares at 3.4 and 4.5 μm, with a peak time delay of ~180 days. The mid-IR LCs are explained as the echo of UV photons by a dust medium with a radius of 5 × 10^(17) cm, consistent with E(B − V) of 0.58 inferred from the spectra. This event is very energetic with an extinction corrected L_(bol) ~ 4 × 10^(44) erg s^(−1). Optical spectra over 400 days in the plateau phase revealed newly formed broad Hα, β emission with a FWHM of ~3750 km s^(−1) and narrow coronal lines such as [Fe VII], [Ne V]. This flare also has a steeply rising UV continuum, detected by multi-epoch Swift data at +700 to +900 days post optical peak. The broad Balmer lines and the UV continuum do not show significant temporal variations. The slow evolving LCs over 1200 days, the constant Balmer lines, and UV continuum at late times rule out tidal disruption event and SN IIn as the physical model for this event. We propose that this event is a "turn-on" AGN, transitioning from a quiescent state to a type-1 AGN with a sub-Eddington accretion rate of 0.017 M⊙ yr^(−1). This change occurred on a very short timescale of ~120–200 days. The discovery of such a rapid "turn-on" AGN poses challenges to accretion disk theories and suggests more future detections of similar events.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Yan, Lin0000-0003-1710-9339
Wang, Tinggui0000-0002-1517-6792
Jiang, Ning0000-0002-7152-3621
Stern, Daniel0000-0003-2686-9241
Dou, Liming0000-0002-4757-8622
Fremling, C.0000-0002-4223-103X
Graham, M. J.0000-0002-3168-0139
Yang, Chenwei0000-0003-4975-2433
Burdge, K.0000-0002-7226-836X
Kasliwal, M. M.0000-0002-5619-4938
Additional Information:© 2019 The American Astronomical Society. Received 2018 November 27; revised 2019 February 5; accepted 2019 February 11; published 2019 March 20. We thank A. Ho, M. Kuhn from Caltech, T. Hung, and S. Frederick from University of Maryland for helping with taking some of the spectral observations. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We also use the 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 the National Aeronautics and Space Administration. This paper also utilized the publicly available SDSS data sets. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS website is The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The participating institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, the University of Basel, the University of Cambridge, Case Western Reserve University, the University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, the University of Pittsburgh, the University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. 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. The observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Palomar - , Keck - , WISE - Wide-field Infrared Survey Explorer, Swift - Swift Gamma-Ray Burst Mission.
Group:Astronomy Department
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Japanese MonbukagakushoUNSPECIFIED
Max Planck SocietyUNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: nuclei – stars: flare – supernovae: general
Issue or Number:1
Record Number:CaltechAUTHORS:20190321-131841379
Persistent URL:
Official Citation:Lin Yan et al 2019 ApJ 874 44
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94024
Deposited By: Tony Diaz
Deposited On:21 Mar 2019 21:54
Last Modified:28 Oct 2019 19:45

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