V723 Monocerotis

V723 Monocerotis

A visual band light curve for V723 Monocerotis, adapted from Jayasinghe et al. (2021)[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Monoceros
Right ascension 06h 29m 04.659s[2]
Declination −05° 34′ 20.23″[2]
Apparent magnitude (V) 8.21 - 8.42[3]
Characteristics
Spectral type G0II[4]
Variable type Ellipsoidal[5]
Astrometry
Proper motion (μ) RA: −1.347 mas/yr[2]
Dec.: 16.140 mas/yr[2]
Parallax (π)2.1748 ± 0.0331 mas[2]
Distance1,500 ± 20 ly
(460 ± 7 pc)
Absolute magnitude (MV)+0.93[6]
Orbit[1]
Period (P)59.9398 d
Eccentricity (e)0 (fixed)
Inclination (i)87.0+1.7
−1.4°
Argument of periastron (ω)
(secondary)		0 (fixed)°
Details
Giant star
Mass0.44±0.06[5] M☉
Radius22.5±1.0[5] R☉
Luminosity173±8[1] L☉
Surface gravity (log g)1.7±0.1[1] cgs
Temperature3,800±100[5] K
Metallicity [Fe/H]−0.9±0.1[1] dex
Rotational velocity (v sin i)15±2[5] km/s
Age5.4+5.1
−2.6[1] Gyr
Stripped subgiant
Mass2.8±0.3[5] M☉
Radius8.3±0.4[5] R☉
Temperature5,800±200[5] K
Rotational velocity (v sin i)70±10[5] km/s
Other designations
V723 Mon, BD−05 1649, HD 45762, HIP 30891, SAO 133321, PPM 189220[7]
Database references
SIMBADdata

V723 Monocerotis is a variable star in the constellation Monoceros. It was proposed in 2021 to be a binary system including a lower mass gap black hole candidate nicknamed "The Unicorn".[1] Located 1,500 light years from Earth, it would be the closest black hole to our planet, and among the smallest ever found.[8][9]

Located in the Monoceros constellation, V723 Monocerotis is an eighth-magnitude ellipsoidal variable yellow giant star roughly the mass of the Sun, but 25 times its radius. The accompanying black hole was proposed to have a mass 3 times the mass of the Sun, corresponding to a Schwarzschild radius of 9 kilometers.[10][11]

Follow-up work in 2022 argued that V723 Monocerotis does not contain a black hole, but is a mass-transfer binary containing a red giant and a subgiant star that has been stripped of much of its mass.[5]

  1. ^ a b c d e f g Cite error: The named reference Jayasinghe_et_al_2021 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference edr3 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference vsx was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Houk_Swift_1999 was invoked but never defined (see the help page).
  5. ^ a b c d e f g h i j Cite error: The named reference elbadry2022 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference strassmeier2000 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference NG2021 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference reuters2021 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SnT2021 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference BBC was invoked but never defined (see the help page).