V810 Centauri

V810 Cen A/B

Observation data Epoch J2000      Equinox J2000
Constellation	Centaurus
Right ascension	11h 43m 31.193s
Declination	–62° 29′ 21.82″
Apparent magnitude (V)	5.021var
Characteristics
Spectral type	F8Ia / B0III
U−B color index	1.762
B−V color index	0.014
Variable type	Semi-regular
Astrometry
Radial velocity (Rv)	16.44 km/s
Proper motion (μ)	RA: –5.74 ± 0.21 mas/yr Dec.: 1.30 ± 0.17 mas/yr
Parallax (π)	0.46 ± 0.22 mas
Distance	3,300 - 3,500 pc
Absolute magnitude (MV)	-8.4/-5.1
Details
Mass	20/25 M☉
Radius	420/14 R☉
Luminosity	200,000/125,000 L☉
Surface gravity (log g)	0.7/3.5 cgs
Temperature	6,010/29,000 K
Age	6-10 million years
Other designations
HIP 57175, SAO 251555, CD-61° 3163, HR 4511, CPD-61° 2559, HD 101947.
Database references
SIMBAD	data

V810 Centauri is a double star consisting of a yellow supergiant primary (V810 Cen A) and blue giant secondary (V810 Cen B). It is a small amplitude variable star, entirely due to the supergiant primary which is visually over three magnitudes brighter than the secondary.

V810 Cen A shows semi-regular variations with several component periods. The dominant mode is around 156 days and corresponds to Cepheid fundamental mode radial pulsation. Without the other pulsation modes it would be considered a Classical Cepheid variable. Other pulsation modes have been detected at 89 to 234 days, with the strongest being a possible non-radial p-mode at 107 days and a possible non-radial g-mode at 185 days.

The blue giant secondary has a similar mass and luminosity to the supergiant primary, but is visually much fainter. The primary is expected to have lost around 5 M_☉ since it was on the main sequence, and has expanded and cooled so it lies at the blue edge of the Cepheid instability strip. It is expected to get no cooler and may perform a blue loop while slowly increasing in luminosity.

V810 Cen was once thought to be a member of the Stock 14 open cluster at 2.6 kpc, but now appears to be more distant. The distance derived from spectrophotometric study is larger than the mean Hipparcos parallax value but within the margin of error.