V373 Cas is a binary star system in the northern constellation Cassiopeia. It is a suspected eclipsing binary with an apparent visual magnitude that decreases from a baseline of 6.03 down to 6.13.[3] The system is located at a distance of approximately 6,200 light years from the Sun, but is drifting closer with a radial velocity of around −25.5 km/s.[4]

V373 Cassiopeiae

V373 Cassiopeiae (center) in optical light. The bright yellow star to the upper right of V373 Cas is ρ Cas.
Observation data Epoch J2000      Equinox J2000
Constellation	Cassiopeia
Right ascension	23h 55m 33.83878s[1]
Declination	+57° 24′ 43.8057″[1]
Apparent magnitude (V)	6.03[2]
Characteristics
Spectral type	B0.5II + B4III/V[2]
B−V color index	0.155±0.005[2]
Variable type	Eclipsing?[3]
Astrometry
Radial velocity (Rv)	−25.5±0.9[4] km/s
Proper motion (μ)	RA: −4.098[1] mas/yr Dec.: −0.101[1] mas/yr
Parallax (π)	0.5267 ± 0.0583 mas[1]
Distance	approx. 6,200 ly (approx. 1,900 pc)
Orbit[5]
Period (P)	13.41921 days
Eccentricity (e)	0.126±0.019
Periastron epoch (T)	2,420,801.98 JD
Argument of periastron (ω) (secondary)	16±8°
Semi-amplitude (K1) (primary)	106.7±2.7 km/s
Semi-amplitude (K2) (secondary)	144.6±2.6 km/s
Details[6]
A
Mass	18.6±2.4 M☉
Surface gravity (log g)	3.0±0.2 cgs
Temperature	23,200±600 K
Rotational velocity (v sin i)	130±10 km/s
Age	7–8 Myr
B
Mass	14.2±1.9 M☉
Surface gravity (log g)	3.5±0.2 cgs
Temperature	26,800±1,500 K
Rotational velocity (v sin i)	60±5 km/s
Other designations
V373 Cas, BD+56°3115, GC 33184, HD 224151, HIP 117957, HR 9052, SAO 35899[7]
Database references
SIMBAD	data

The binary nature of this system was announced in 1912 by Walter S. Adams.[9] It is a double-lined spectroscopic binary with an orbital period of 13.4 days and an eccentricity of 0.13.[5] The system was found to be variable in 1958 by C. Roger Lynds, and the variability cycle was shown to be related to the orbital period.[9] It has been described as a heartbeat star rather than an eclipsing system. This is a type of pulsating star where the pulsations are induced by the tidal attraction of a close companion.[10]

V373 Cas is composed of two hot blue-white giant stars that have exhausted their core hydrogen and expanded off the main sequence. Lyubimkov and colleagues analysed spectral and radial velocity to calculate that the stars were ~19 and ~15 times as massive as the Sun and the age of the system is around 7-8 million years old.[6] The primary component is the more evolved and now comes close to filling its Roche lobe when it is at periastron.[11]

References