2021MNRAS.504.2577J -
Mon. Not. R. Astron. Soc., 504, 2577-2602 (2021/June-3)
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., STANEK K.Z., THOMPSON T.A., KOCHANEK C.S., ROWAN D.M., VALLELY P.J., STRASSMEIER K.G., WEBER M., HINKLE J.T., HAMBSCH F.-J., MARTIN D.V., PRIETO J.L., PESSI T., HUBER D., AUCHETTL K., LOPEZ L.A., ILYIN I., BADENES C., HOWARD A.W., ISAACSON H. and MURPHY S.J.
Abstract (from CDS):
We report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby (d∼460 pc), bright (V ≃ 8.3 mag), evolved (T_eff, giant_ ≃ 4440 K, and Lgiant ≃ 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 Mcomp = 3.04 ± 0.06 M☉, a stellar radius of Rgiant = 24.9 ± 0.7 R☉, and a giant mass of Mgiant = 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/Ledd ∼ 10–9. The simplest explanation for the massive companion is a single compact object, most likely a black hole in the 'mass gap'.
Abstract Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Journal keyword(s):
binaries: spectroscopic - stars: black holes - stars: individual: V723 Mon
Simbad objects:
11
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