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Spikey: self-lensing flares from eccentric SMBH binaries

Hu, Betty X. and D'Orazio, Daniel J. and Haiman, Zoltán and Smith, Krista Lynne and Snios, Bradford and Charisi, Maria and Di Stefano, Rosanne (2020) Spikey: self-lensing flares from eccentric SMBH binaries. Monthly Notices of the Royal Astronomical Society, 495 (4). pp. 4061-4070. ISSN 0035-8711.

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We examine the light curves of two quasars, motivated by recent suggestions that a supermassive black hole binary (SMBHB) can exhibit sharp lensing spikes. We model the variability of each light curve as due to a combination of two relativistic effects: the orbital relativistic Doppler boost and gravitational binary self-lensing. In order to model each system, we extend previous Doppler plus self-lensing models to include eccentricity. The first quasar is identified in optical data as a binary candidate with a 20-yr period (Ark 120), and shows a prominent spike. For this source, we rule out the lensing hypothesis and disfavour the Doppler-boost hypothesis due to discrepancies in the measured versus recovered values of the binary mass and optical spectral slope. The second source, which we nickname Spikey, is the rare case of an active galactic nucleus identified in Kepler’s high-quality, high-cadence photometric data. For this source, we find a model, consisting of a combination of Doppler modulation and a narrow symmetric lensing spike, consistent with an eccentric SMBHB with a mass of M_(tot) =3 × 10⁷ M_⊙⁠, rest-frame orbital period T = 418 d, eccentricity e = 0.5, and seen at an inclination of 8○ from edge-on. This interpretation can be tested by monitoring Spikey for periodic behaviour and recurring flares in the next few years. In preparation for such monitoring, we present the first X-ray observations of this object taken by the Neil Gehrels Swift Observatory.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
D'Orazio, Daniel J.0000-0002-1271-6247
Haiman, Zoltán0000-0003-3633-5403
Smith, Krista Lynne0000-0001-5785-7038
Snios, Bradford0000-0002-4900-928X
Charisi, Maria0000-0003-3579-2522
Di Stefano, Rosanne0000-0003-0972-1376
Alternate Title:Spikey: A Search for Lensing Flares from SMBH Binaries
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 May 5. Received 2020 May 5; in original form 2019 October 11. The authors thank Alberto Sesana, Thomas Kupfer, and Matthew Graham for useful discussions. DJD acknowledges support from NASA through Einstein Postdoctoral Fellowship award number PF6-170151 and funding from the Institute for Theory and Computation Fellowship. ZH acknowledges support from NSF grant 1715661 and NASA grants NNX17AL82G and 80NSSC19K0149. KLS acknowledges support from Einstein Postdoctoral Fellowship award number PF7-180168. MC acknowledges support from the National Science Foundation (NSF) NANOGrav Physics Frontier Center, award number 1430284. Funding for this work was partially provided through Swift proposal #1518206. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate.
Funding AgencyGrant Number
NASA Einstein FellowshipPF6-170151
Institute for Theory and ComputationUNSPECIFIED
NASA Einstein FellowshipPF7-180168
Subject Keywords:gravitational lensing: micro, quasars: supermassive black holes
Issue or Number:4
Record Number:CaltechAUTHORS:20200723-122440653
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Official Citation:Betty X Hu, Daniel J D’Orazio, Zoltán Haiman, Krista Lynne Smith, Bradford Snios, Maria Charisi, Rosanne Di Stefano, Spikey: self-lensing flares from eccentric SMBH binaries, Monthly Notices of the Royal Astronomical Society, Volume 495, Issue 4, July 2020, Pages 4061–4070,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104538
Deposited By: George Porter
Deposited On:23 Jul 2020 19:58
Last Modified:23 Jul 2020 19:58

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