HD 21278

HD 21278 is a binary star[7] system in the constellation Perseus, located within the 60±7[6] million year old Alpha Persei Cluster.[7] It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of 4.99.[2] The system is located at a distance of approximately 580 light years from the Sun based on parallax,[1] and it is drifting further away with a radial velocity of +1.20 km/s.[5]

HD 21278
Location of HD 21278 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 03h 28m 03.07229s[1]
Declination 49° 03′ 46.3315″[1]
Apparent magnitude (V) 4.99[2]
Characteristics
Spectral type B5V[3]
U−B color index −0.56[4]
B−V color index −0.10[4]
Astrometry
Radial velocity (Rv)+1.20[5] km/s
Proper motion (μ) RA: +21.784[1] mas/yr
Dec.: −26.036[1] mas/yr
Parallax (π)5.6334 ± 0.2298[1] mas
Distance580 ± 20 ly
(178 ± 7 pc)
Absolute magnitude (MV)−1.49[6]
Orbit[7]
Period (P)21.695±0.004 d
Semi-major axis (a)≥6.72 Gm
Eccentricity (e)0.12±0.04
Periastron epoch (T)24,446,714.5±0.2
Argument of periastron (ω)
(secondary)		109±3°
Semi-amplitude (K1)
(primary)		22.7±0.9 km/s
Semi-amplitude (K2)
(secondary)		49±3 km/s
Details
A
Mass4.597[8] M☉
Radius3.9[9] R☉
Luminosity940[6] L☉
Surface gravity (log g)4.152±0.113[10] cgs
Temperature15,274±244[10] K
Metallicity [Fe/H]0.00[11] dex
Rotational velocity (v sin i)75[10] km/s
Age187[11] or 60[6] Myr
Other designations
BD+48°920, GC 4108, HD 21278, HIP 16147, HR 1034, SAO 38849[12]
Database references
SIMBADdata

The binary nature of this star was announced in 1925 by Otto Struve.[13] It is a double-lined spectroscopic binary with an orbital period of 21.7 days and an eccentricity of 0.12.[7]

The primary component is a B-type main-sequence star with a stellar classification of B5V,[3] indicating it is generating energy through core hydrogen fusion. The star is spinning with a projected rotational velocity of 75 km/s.[10] It has 4.6[8] times the mass of the Sun and about 3.9[9] times the Sun's radius. HD 21278 is radiating 940[6] times the luminosity of the Sun from its photosphere at an effective temperature of 15,274 K.[10]

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. 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. Vizier catalog entry
  3. Zuckerman, B.; et al. (June 2012). "Stellar Membership and Dusty Debris Disks in the α Persei Cluster". The Astrophysical Journal. 752 (1): 12. arXiv:1204.3950. Bibcode:2012ApJ...752...58Z. doi:10.1088/0004-637X/752/1/58. 58.
  4. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42: 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  5. Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
  6. Silaj, J.; Landstreet, J. D. (2014). "Accurate age determinations of several nearby open clusters containing magnetic Ap stars". Astronomy & Astrophysics. 566: A132. arXiv:1407.4531. Bibcode:2014A&A...566A.132S. doi:10.1051/0004-6361/201321468.
  7. Morrell, Nidia; Abt, Helmut A. (July 10, 1992). "Spectroscopic binaries in the Alpha Persei cluster". Astrophysical Journal, Part 1. 393 (2): 666–673. Bibcode:1992ApJ...393..666M. doi:10.1086/171534.
  8. Sheikhi, Najmeh; et al. (March 2016). "The binary fraction and mass segregation in Alpha Persei open cluster". Monthly Notices of the Royal Astronomical Society. 457 (1): 1028–1036. arXiv:1601.02186. Bibcode:2016MNRAS.457.1028S. doi:10.1093/mnras/stw059.
  9. Pasinetti Fracassini, L. E.; et al. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)". Astronomy & Astrophysics (Third ed.). 367 (2): 521–24. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451.
  10. David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146.
  11. Gontcharov, G. A. (2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031.
  12. "HD 21278". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-16.
  13. Struve, O. (December 1925). "Twelve new spectroscopic binaries". Astrophysical Journal. 62: 434–434. Bibcode:1925ApJ....62..434S. doi:10.1086/142944.
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