HD 89890

HD 89890 is the brightest member of a multiple star system with at least four components,^[5] located in the southern constellation of Vela. It is visible to the naked eye with an apparent visual magnitude of 4.50.^[4] The annual parallax shift of 2.6 mas^[3] provides a distance estimate of around 1,200 light-years (370 parsecs). It is moving further away from Earth with a heliocentric radial velocity of +10 km/s.^[2]

HD 89890

A visual band light curve for MV Velorum, adapted from Sterken et al. (1996)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Vela[2]
Right ascension	10h 20m 54.77319s[3]
Declination	−56° 02′ 35.5728″[3]
Apparent magnitude (V)	4.50[4]
Characteristics
Spectral type	B3 III + A0 IVpSi + A2 + K0 III[5]
B−V color index	−0.102±0.014 (A + B)[2]
Astrometry
Radial velocity (Rv)	+10.4±2.8[2] km/s
Proper motion (μ)	RA: −7.5[6] mas/yr Dec.: +4.0[6] mas/yr
Parallax (π)	2.6564±0.2314 mas[3]
Distance	1,200 ± 100 ly (380 ± 30 pc)
Absolute magnitude (MV)	−3.21 (A + B)[2]
Details
A (HD 89890)
Radius	10.07±0.20[7] R☉
Luminosity	3,082.41[2] L☉
Surface gravity (log g)	3.00±0.03[7] cgs
Temperature	15,000±150[7] K
Rotational velocity (v sin i)	26.8±0.5[7] km/s
Other designations
WDS J10209-5603[8]
A+B: CPD−55 3286, HIP 50676, HR 4074[8]
A: J Velorum, MV Velorum, HD 89890, SAO 237959, TYC 8604-975-1[8]
B: SAO 237960, TYC 8604-2444-1[8]
C: CD−55 3306, SAO 237958, TYC 8604-2137-1[8]
Database references
SIMBAD	HD 89890 (A)
	HIC 50676 (A+B)
	TYC 8604-2444-1 (B)
	CD-55 3306 (C)

System

The Washington Double Star Catalog lists three visible components for this system. The brightest, component A, is of visual magnitude 4.50. Component B has a magnitude of 7.179,^[9] and as of 2000 lies at an angular separation of 7.10″ from A, along a position angle (PA) of 102°. Component C is a magnitude 9.125 star^[9] at a separation of 36.20″ from A at a PA of 191°. The physical link between the stars was described on the basis of their dynamic parallax and mean velocities.^[10] The three components A, B and C have Gaia Data Release 2 parallaxes of 2.6564±0.2314 mas, 2.1771±0.0490 mas, and 1.6097±0.0400 mas, respectively.^[3]

Properties

Component A has a stellar classification of B3 III, and is categorized as a Be star. It shows photometric variations with multiple periods around 4.6 days and line-profile variations with a period of 2.318 days. The radial velocity of this star is constant.^[5] It has 10^[7] times the Sun's radius and shines with 3,082^[2] times the Sun's luminosity from its photosphere at an effective temperature of 15,000 K.^[7]

The component B shows a variation in spectra consistent with being a double-lined spectroscopic binary. The brighter member (Ba) is a silicon star with a class of A0 IVpSi, while the fainter component (Bb) is of type A2. Component C has a class of K0 III, indicating it is an evolved giant star. The measured effective temperature of C is 5,500 K. The fact that component A most likely shares a common origin with C suggests that the former is much older than expected, and may actually be a blue straggler formed from the merger of a close binary. This could have been caused by the gravitational influence of an unseen companion of A.^[5]