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A unicorn in Monoceros: the 3 M_⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate

Jayasinghe, T. and Stanek, K. Z. and Thompson, Todd A. and Kochanek, C. S. and Rowan, D. M. and Vallely, P. J. and Strassmeier, K. G. and Weber, M. and Hinkle, J. T. and Hambsch, F.-J. and Martin, D. V. and Prieto, J. L. and Pessi, T. and Huber, D. and Auchettl, K. and Lopez, L. A. and Ilyin, I. and Badenes, C. and Howard, A. W. and Isaacson, H. and Murphy, S. J. (2021) A unicorn in Monoceros: the 3 M_⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate. Monthly Notices of the Royal Astronomical Society, 504 (2). pp. 2577-2602. ISSN 0035-8711. doi:10.1093/mnras/stab907.

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We report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby (⁠d∼460pc⁠), bright (V ≃ 8.3 mag), evolved (T_(eff, giant) ≃ 4440 K, and L_(giant) ≃ 173 L_⊙) red giant in a high mass function, f(M) = 1.72 ± 0.01 M_⊙, nearly circular binary (P = 59.9 d, e ≃ 0). V723 Mon is a known variable star, previously classified as an eclipsing binary, but its All-Sky Automated Survey, Kilodegree Extremely Little Telescope, and Transiting Exoplanet Survey Satellite light curves are those of a nearly edge-on ellipsoidal variable. Detailed models of the light curves constrained by the period, radial velocities, and stellar temperature give an inclination of 87.0∘^(+1.7∘)_(−1.4∘)⁠, a mass ratio of q ≃ 0.33 ± 0.02, a companion mass of M_(comp) = 3.04 ± 0.06 M_⊙, a stellar radius of R_(giant) = 24.9 ± 0.7 R_⊙, and a giant mass of M_(giant) = 1.00 ± 0.07 M_⊙. We identify a likely non-stellar, diffuse veiling component with contributions in the B and V band of ∼63 per cent and ∼24 per cent⁠, respectively. The SED and the absence of continuum eclipses imply that the companion mass must be dominated by a compact object. We do observe eclipses of the Balmer lines when the dark companion passes behind the giant, but their velocity spreads are low compared to observed accretion discs. The X-ray luminosity of the system is L_X ≃ 7.6 × 10²⁹ ergs s⁻¹⁠, corresponding to L/L_(edd) ∼ 10⁻⁹. The simplest explanation for the massive companion is a single compact object, most likely a black hole in the ‘mass gap’.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jayasinghe, T.0000-0002-6244-477X
Thompson, Todd A.0000-0003-2377-9574
Kochanek, C. S.0000-0001-6017-2961
Rowan, D. M.0000-0003-2431-981X
Vallely, P. J.0000-0001-5661-7155
Strassmeier, K. G.0000-0002-6192-6494
Hinkle, J. T.0000-0001-9668-2920
Prieto, J. L.0000-0003-1072-2712
Huber, D.0000-0001-8832-4488
Auchettl, K.0000-0002-4449-9152
Lopez, L. A.0000-0002-1790-3148
Badenes, C.0000-0003-3494-343X
Howard, A. W.0000-0001-8638-0320
Isaacson, H.0000-0002-0531-1073
Murphy, S. J.0000-0002-5648-3107
Alternate Title:A unicorn in monoceros: the 3 M⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 March 26. Received 2021 March 16; in original form 2021 January 6. Published: 01 May 2021. We thank the referee, Dr. Jerome Orosz, for his useful comments on this manuscript. We thank Dr. Jennifer Johnson, Dr. Marc Pinsonneault, Dr. Jim Fuller, and Dr. Kento Masuda for useful discussions on this manuscript. We thank Dr. Jay Strader for a careful reading of this manuscript. We thank Dr. Rick Pogge for his help with obtaining the LBT/MODS spectra. The ASAS-SN team at OSU is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, and NSF grant AST-1908570. TJ, KZS, and CSK are supported by NSF grants AST-1814440 and AST-1908570. TJ acknowledges support from the Ohio State Presidential Fellowship. TAT is supported in part by NASA grant 80NSSC20K0531. TAT acknowledges previous support from Scialog Scholar grant 24216 from the Research Corporation, from which this effort germinated. JTH is supported by NASA award 80NSSC21K0136. Support for JLP is provided in part by the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. DH acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379), and the National Science Foundation (AST-1717000). CB acknowledges support from the National Science Foundation grant AST-1909022. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are as follows: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, representing OSU, University of Notre Dame, University of Minnesota, and University of Virginia. STELLA and PEPSI were made possible by funding through the State of Brandenburg (MWFK) and the German Federal Ministry of Education and Research (BMBF) through their Verbundforschung grants 05AL2BA1/3 and 05A08BAC. This research is based on observations made with the Neil Gehrels Swift Observatory, obtained from the MAST data archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. 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. We thank the ASAS and KELT projects for making their light-curve data publicly available. This research has used the VizieR catalogue access tool, CDS, Strasbourg, France. This research also used ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013, 2018). Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF5490
Ohio State UniversityUNSPECIFIED
Research Corporation242167
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Alfred P. Sloan FoundationUNSPECIFIED
Australian Research CouncilCE170100013
State of BrandenburgUNSPECIFIED
Bundesministerium für Bildung und Forschung (BMBF)05AL2BA1/3
Bundesministerium für Bildung und Forschung (BMBF)05A08BAC
NASANAS 5-26555
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: spectroscopic – stars: black holes – stars: individual: V723 Mon
Issue or Number:2
Record Number:CaltechAUTHORS:20210729-154631377
Persistent URL:
Official Citation:T Jayasinghe, K Z Stanek, Todd A Thompson, C S Kochanek, D M Rowan, P J Vallely, K G Strassmeier, M Weber, J T Hinkle, F-J Hambsch, D V Martin, J L Prieto, T Pessi, D Huber, K Auchettl, L A Lopez, I Ilyin, C Badenes, A W Howard, H Isaacson, S J Murphy, A unicorn in monoceros: the 3 M⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate, Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 2, June 2021, Pages 2577–2602,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110064
Deposited By: Tony Diaz
Deposited On:02 Aug 2021 19:01
Last Modified:15 Sep 2021 21:20

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