HD 89890

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

HD 89890
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 10h 20m 54.77319s[1]
Declination −56° 02′ 35.5728″[1]
Apparent magnitude (V) 4.50[2]
Characteristics
Spectral type B3 III + A0 IVpSi + A2 + K0 III[3]
B−V color index −0.102±0.014 (A + B)[4]
Astrometry
Radial velocity (Rv)+10.4±2.8[4] km/s
Proper motion (μ) RA: −7.5[5] mas/yr
Dec.: +4.0[5] mas/yr
Parallax (π)2.6564 ± 0.2314[1] mas
Distance1,200 ± 100 ly
(380 ± 30 pc)
Absolute magnitude (MV)−3.21 (A + B)[4]
Details
A (HD 89890)
Radius10.07±0.20[6] R☉
Luminosity3,082.41[4] L☉
Surface gravity (log g)3.00±0.03[6] cgs
Temperature15,000±150[6] K
Rotational velocity (v sin i)26.8±0.5[6] km/s
Other designations
WDS J10209-5603[7]
A+B: CPD−55 3286, HIP 50676, HR 4074[7]
A: J Velorum, MV Velorum, HD 89890, SAO 237959, TYC 8604-975-1[7]
B: SAO 237960, TYC 8604-2444-1[7]
C: CD−55 3306, SAO 237958, TYC 8604-2137-1[7]
Database references
SIMBADHD 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,[8] 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[8] 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.[9] 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.[1]

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.[3] It has 10[6] times the Sun's radius and shines with 3,082[4] times the Sun's luminosity from its photosphere at an effective temperature of 15,000 K.[6]

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.[3]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Jaschek, M; Egret, D; Jaschek, M; Groth, H. -G (1982). "Catalog of Be stars". Be Stars. 98: 261–263. Bibcode:1982IAUS...98..261J. doi:10.1007/978-94-009-8565-0_44. ISBN 978-90-277-1367-4.
  3. Veramendi, M. E.; González, J. F. (July 2014), "Spectroscopic study of early-type multiple stellar systems. II. New binary subsystems", Astronomy & Astrophysics, 567: 10, arXiv:1405.1084, Bibcode:2014A&A...567A..35V, doi:10.1051/0004-6361/201423736, S2CID 21711755, A35.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  5. Röser, S.; Bastian, U. (September 1988), "A New Star Catalogue of SAO Type", Astronomy and Astrophysics Supplement Series, 74: 449, Bibcode:1988A&AS...74..449R.
  6. Arcos, C.; et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society, 474 (4): 5287–5299, arXiv:1711.08675, Bibcode:2018MNRAS.474.5287A, doi:10.1093/mnras/stx3075, S2CID 74872624.
  7. "HD 89890". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-08-08.
  8. Høg, E.; et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN 978-0333750889.
  9. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
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