HD 21071

HD 21071 is a blue-white hued variable star in the northern constellation of Perseus. It is a sixth magnitude star that is dimly visible to the naked eye under good viewing conditions, having an apparent visual magnitude of 6.09.[2] The brightness of the star varies with a multiperiodic cycle.[8] The distance to HD 21071, as determined from an annual parallax shift of 6.03 mas,[1] is 541 light years. It is a member of the young Alpha Persei cluster, Melotte 20,[3][9] and moving is closer to the Earth with a heliocentric radial velocity of −1.5 km/s.[5]

HD 21071
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 03h 25m 57.38167s[1]
Declination +49° 07′ 14.7332″[1]
Apparent magnitude (V) 6.09[2]
Characteristics
Spectral type B7 V[3]
B−V color index −0.073±0.005[2]
Variable type SPB[4]
Astrometry
Radial velocity (Rv)−1.5±0.9[5] km/s
Proper motion (μ) RA: +24.008[1] mas/yr
Dec.: −26.870[1] mas/yr
Parallax (π)6.0326 ± 0.0660[1] mas
Distance541 ± 6 ly
(166 ± 2 pc)
Absolute magnitude (MV)−0.19[2]
Details
Mass3.69+0.14
−0.15[4] M☉
Radius2.21[6] R☉
Luminosity278.0+53.1
−44.7[4] L☉
Surface gravity (log g)4.30[3] cgs
Temperature14,768[3] K
Metallicity [Fe/H]0.0082+0.0053
−0.0032[4] dex
Rotational velocity (v sin i)58[3] km/s
Age90[3] Myr
Other designations
V576 Per, BD+48° 913, GC 4075, HD 21071, HIP 15988, HR 1029, SAO 38817[7]
Database references
SIMBADdata

This is a B-type main-sequence star with a stellar classification of B7 V.[3] HD 21071 belongs to an unusual stellar population termed 'sn' stars. These seem to be related to chemically peculiar stars, but have sharp ('s') Balmer and metal absorption lines with "broad coreless He I" ('n') lines. The latter wide, "nebulous" lines may be due to Stark broadening caused by an electric field.[3] HD 21071 is a slowly pulsating B-type star (SPB star) that was initially found to vary with a period of 0.84 days. Further study revealed four frequencies, with the two dominant, higher amplitude frequencies having similar cycles of 1.19 and 1.15 per day.[4]

Pulsation Periods[4]
ID Frequency
(d−1)		 V Amplitude
(mmag)		 Radial Velocity
(km/s)
1 1.18843 18.5 3.28±0.85
2 1.14934 7.7 –
3 1.41968 3.8 –
4 0.95706 3.0 –

Stellar models show the star to have 3.7[4] times the mass of the Sun, with 2.21[6] times the Sun's radius. It is 90[3] million years old with a near-solar metallicity and is spinning with a projected rotational velocity of 58 km/s.[3] The star is radiating 278[4] times the Sun's luminosity from its photosphere at an effective temperature of 14,768 K.[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.
  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.
  3. Saffe, C.; Levato, H. (February 2014), "On the nature of sn stars. I. A detailed abundance study", Astronomy & Astrophysics, 562: 17, arXiv:1401.5764, Bibcode:2014A&A...562A.128S, doi:10.1051/0004-6361/201322091, A128.
  4. Szewczuk, W.; Daszyńska-Daszkiewicz, J. (October 2015), "Seismic modelling of the rotating, slowly pulsating B-type star HD 21071", Monthly Notices of the Royal Astronomical Society, 453 (1): 277–286, arXiv:1507.03609, Bibcode:2015MNRAS.453..277S, doi:10.1093/mnras/stv1589.
  5. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  6. Mathias, P.; et al. (December 2001), "Spectroscopic monitoring of 10 new northern slowly pulsating B star candidates discovered from the HIPPARCOS mission", Astronomy and Astrophysics, 379: 905–916, Bibcode:2001A&A...379..905M, doi:10.1051/0004-6361:20011406.
  7. "HD 21071". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 26, 2018.
  8. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  9. 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.
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