HY Velorum

HY Velorum is a binary star^[7] system in the southern constellation of Vela. It is a dim star but visible to the naked eye with an apparent visual magnitude of 4.83.^[5] The distance to this system, as estimated from its annual parallax shift of 7.1 mas,^[2] is 460 light years. HY Vel most likely forms a gravitationally bound pair with the magnitude 5.45 binary system KT Vel (HD 74535);^[12] both are members of the IC 2391 open cluster.^[13] As of 1998, HY Vel and KT Vel had an angular separation of 76.1″ along a position angle of 311°.^[14]

HY Velorum

A visual band light curve for HY Velorum, adapted from Waelkens and Rufener (1985)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Vela
Right ascension	08h 42m 25.38667s[2]
Declination	−53° 06′ 50.3324″[2]
Apparent magnitude (V)	4.81 - 4.86[3]
Characteristics
Spectral type	B3 IV[4]
B−V color index	−0.173±0.007[5]
Variable type	SPB[3]
Astrometry
Radial velocity (Rv)	+15.6±0.2[5] km/s
Proper motion (μ)	RA: −24.83[6] mas/yr Dec.: +23.21[6] mas/yr
Parallax (π)	7.1141±0.2302 mas[2]
Distance	460 ± 10 ly (141 ± 5 pc)
Absolute magnitude (MV)	−1.25[5]
Orbit[7]
Period (P)	8.378±0.001 d
Eccentricity (e)	0.24±0.04
Periastron epoch (T)	2450741.3 ± 0.2 HJD
Argument of periastron (ω) (secondary)	93±9°
Semi-amplitude (K1) (primary)	8.0±0.3 km/s
Details
HY Vel Aa
Mass	5.4[8] M☉
Luminosity	830+927 −743[8] L☉
Surface gravity (log g)	4.07[9] cgs
Temperature	16,865+235 −231[8] K
Metallicity [Fe/H]	0.03±0.02[9] dex
Rotational velocity (v sin i)	45[8] km/s
Age	179[10] Myr
Other designations
HY Vel, CPD−52° 1607, HD 74560, HIP 42726, HR 3467, SAO 236205, WDS J08424-5307A[11]
Database references
SIMBAD	data

This is a single-lined spectroscopic binary system with an orbital period of 8.4 days and an eccentricity of 0.24. The visible component has an a sin i value of 0.006 AU, where a is the semimajor axis and i is the (unknown) orbital inclination to the line of sight.

In 1979, Shyam M. Jakate announced the discovery that the star's brightness varies.^[15] It was given its variable star designation, HY Velorum, in 1981.^[16] The primary, which is the variable star, is a slowly pulsating B-type star having at least three pulsational modes, with the dominant mode showing a frequency of 0.64472 cycles per day,^[7] corresponding to the catalogued period of 1.55106 days.^[3] It has a stellar classification of B3 IV, matching a B-type subgiant star.^[4]