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Testing the relativistic Doppler boost hypothesis for supermassive black hole binary candidates

Charisi, Maria and Haiman, Zoltán and Schiminovich, David and D’Orazio, Daniel J. (2018) Testing the relativistic Doppler boost hypothesis for supermassive black hole binary candidates. Monthly Notices of the Royal Astronomical Society, 476 (4). pp. 4617-4628. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20180613-101005468

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Abstract

Supermassive black hole binaries (SMBHBs) should be common in galactic nuclei as a result of frequent galaxy mergers. Recently, a large sample of sub-parsec SMBHB candidates was identified as bright periodically variable quasars in optical surveys. If the observed periodicity corresponds to the redshifted binary orbital period, the inferred orbital velocities are relativistic (v/c ≈ 0.1). The optical and ultraviolet (UV) luminosities are expected to arise from gas bound to the individual BHs, and would be modulated by the relativistic Doppler effect. The optical and UV light curves should vary in tandem with relative amplitudes which depend on the respective spectral slopes. We constructed a control sample of 42 quasars with aperiodic variability, to test whether this Doppler colour signature can be distinguished from intrinsic chromatic variability. We found that the Doppler signature can arise by chance in ∼20 per cent (∼37 per cent) of quasars in the nUV (fUV) band. These probabilities reflect the limited quality of the control sample and represent upper limits on how frequently quasars mimic the Doppler brightness+colour variations. We performed separate tests on the periodic quasar candidates, and found that for the majority, the Doppler boost hypothesis requires an unusually steep UV spectrum or an unexpectedly large BH mass and orbital velocity. We conclude that at most approximately one-third of these periodic candidates can harbor Doppler-modulated SMBHBs.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/mnras/sty516DOIArticle
https://arxiv.org/abs/1801.06189arXivDiscussion Paper
ORCID:
AuthorORCID
Charisi, Maria0000-0003-3579-2522
Haiman, Zoltán0000-0003-3633-5403
Additional Information:© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2018 February 21. Received 2018 February 21; in original form 2018 January 17. Published: 28 February 2018. We thank Jules Halpern, Szabi Marka, Imre Bartos, Joe Lazio, Michele Vallisneri, and Matthew Graham for useful discussions and suggestions. MC acknowledges support from the National Science Foundation (NSF) NANOGrav Physics Frontier Center, award number 1430284. Financial support was provided by NASA through grants NNX15AB19G, NNX17AL82G, and 16-SWIFT16-0015, and by NSF grant 1715661. Financial support to DJD was provided from NASA through Einstein Postdoctoral Fellowship award number PF6-170151. ZH also gratefully acknowledges support from a Simons Fellowship in Theoretical Physics and hospitality by NYU.
Group:TAPIR
Funders:
Funding AgencyGrant Number
NSFAST-1430284
NASANNX15AB19G
NASANNX17AL82G
NASA16-SWIFT16-0015
NSFAST-1715661
NASA Einstein FellowshipPF6-170151
Simons FoundationUNSPECIFIED
Subject Keywords:quasars: supermassive black holes
Issue or Number:4
Record Number:CaltechAUTHORS:20180613-101005468
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180613-101005468
Official Citation:Maria Charisi, Zoltán Haiman, David Schiminovich, Daniel J D'Orazio; Testing the relativistic Doppler boost hypothesis for supermassive black hole binary candidates, Monthly Notices of the Royal Astronomical Society, Volume 476, Issue 4, 1 June 2018, Pages 4617–4628, https://doi.org/10.1093/mnras/sty516
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87057
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Jun 2018 18:00
Last Modified:09 Mar 2020 13:18

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