A Unicorn in Monoceros: the $3M_odot$ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate. (arXiv:2101.02212v2 [astro-ph.SR] UPDATED)

A Unicorn in Monoceros: the $3M_odot$ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate. (arXiv:2101.02212v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Jayasinghe_T/0/1/0/all/0/1">T. Jayasinghe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stanek_K/0/1/0/all/0/1">K. Z. Stanek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thompson_T/0/1/0/all/0/1">Todd A. Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kochanek_C/0/1/0/all/0/1">C. S. Kochanek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rowan_D/0/1/0/all/0/1">D. M. Rowan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vallely_P/0/1/0/all/0/1">P. J. Vallely</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strassmeier_K/0/1/0/all/0/1">K. G. Strassmeier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weber_M/0/1/0/all/0/1">M. Weber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hinkle_J/0/1/0/all/0/1">J. T. Hinkle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hambsch_F/0/1/0/all/0/1">F.-J. Hambsch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martin_D/0/1/0/all/0/1">D. Martin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prieto_J/0/1/0/all/0/1">J. L. Prieto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pessi_T/0/1/0/all/0/1">T. Pessi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huber_D/0/1/0/all/0/1">D. Huber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Auchettl_K/0/1/0/all/0/1">K. Auchettl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_L/0/1/0/all/0/1">L. A. Lopez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ilyin_I/0/1/0/all/0/1">I. Ilyin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Badenes_C/0/1/0/all/0/1">C. Badenes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howard_A/0/1/0/all/0/1">A. W. Howard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Isaacson_H/0/1/0/all/0/1">H. Isaacson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murphy_S/0/1/0/all/0/1">S. J. Murphy</a>

We report the discovery of the closest known black hole candidate as a binary
companion to V723 Mon. V723 Mon is a nearby ($dsim460,rm pc$), bright
($Vsimeq8.3$~mag), evolved ($T_{rm eff, giant}simeq4440$~K, and $L_{rm
giant}simeq173~L_odot$) red giant in a high mass function, $f(M)=1.72pm
0.01~M_odot$, nearly circular binary ($P=59.9$ d, $esimeq 0$). V723 Mon is a
known variable star, previously classified as an eclipsing binary, but its
All-Sky Automated Survey (ASAS), Kilodegree Extremely Little Telescope (KELT),
and Transiting Exoplanet Survey Satellite (TESS) 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^circ{}^{+1.7^{circ}}_{-1.4^{circ}} $, a mass ratio of
$qsimeq0.33pm0.02$, a companion mass of $M_{rm comp}=3.04pm0.06~M_odot$, a
stellar radius of $R_{rm giant}=24.9pm0.7~R_odot$, and a giant mass of
$M_{rm giant}=1.00pm0.07~ M_odot$. We identify a likely non-stellar, diffuse
veiling component with contributions in the $B$ and $V$-band of ${sim}63%$
and ${sim}24%$, 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 disks.
The X-ray luminosity of the system is $L_{rm X}simeq7.6times10^{29}~rm
ergs~s^{-1}$, corresponding to $L/L_{rm edd}{sim}10^{-9}$. The simplest
explanation for the massive companion is a single compact object, most likely a
black hole in the “mass gap”.

We report the discovery of the closest known black hole candidate as a binary
companion to V723 Mon. V723 Mon is a nearby ($dsim460,rm pc$), bright
($Vsimeq8.3$~mag), evolved ($T_{rm eff, giant}simeq4440$~K, and $L_{rm
giant}simeq173~L_odot$) red giant in a high mass function, $f(M)=1.72pm
0.01~M_odot$, nearly circular binary ($P=59.9$ d, $esimeq 0$). V723 Mon is a
known variable star, previously classified as an eclipsing binary, but its
All-Sky Automated Survey (ASAS), Kilodegree Extremely Little Telescope (KELT),
and Transiting Exoplanet Survey Satellite (TESS) 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^circ{}^{+1.7^{circ}}_{-1.4^{circ}} $, a mass ratio of
$qsimeq0.33pm0.02$, a companion mass of $M_{rm comp}=3.04pm0.06~M_odot$, a
stellar radius of $R_{rm giant}=24.9pm0.7~R_odot$, and a giant mass of
$M_{rm giant}=1.00pm0.07~ M_odot$. We identify a likely non-stellar, diffuse
veiling component with contributions in the $B$ and $V$-band of ${sim}63%$
and ${sim}24%$, 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 disks.
The X-ray luminosity of the system is $L_{rm X}simeq7.6times10^{29}~rm
ergs~s^{-1}$, corresponding to $L/L_{rm edd}{sim}10^{-9}$. The simplest
explanation for the massive companion is a single compact object, most likely a
black hole in the “mass gap”.

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