b Persei

b Persei (also known as HD 26961) is a spectroscopic triple star in the constellation Perseus. Its apparent magnitude is 4.60,[6] and it is about 320 light years away.[1]

This article is about b Persei. For β Persei, see Algol.
b Persei
Location of b Persei (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Perseus
Right ascension 04h 18m 14.61690s[1]
Declination +50° 17′ 43.8058″[1]
Apparent magnitude (V) 4.52 - 4.68[2]
Characteristics
Spectral type A1III[3]
B−V color index +0.04[4]
Variable type Ellipsoidal[2]
Astrometry
Radial velocity (Rv)19.8±0.9[5] km/s
Proper motion (μ) RA: 45.42±0.40[1] mas/yr
Dec.: −56.72±0.32[1] mas/yr
Parallax (π)10.40 ± 0.35 mas[1]
Distance310 ± 10 ly
(96 ± 3 pc)
Absolute magnitude (MV)0.3[6]
Orbit[7]
PrimaryA or Aa
CompanionC or Ac
Period (P)701.76 days
Semi-major axis (a)5.09 mas
Eccentricity (e)0.235
Inclination (i)83.46°
Longitude of the node (Ω)115.29°
Periastron epoch (T)2440143.3984
Argument of periastron (ω)
(secondary)		263°
Details
A or Aa
Mass2.25[6] M☉
Radius3.2[8] R☉
Luminosity10[9] L☉
Temperature9000[6] K
Rotational velocity (v sin i)81[10] km/s
B or Ab
Mass0.56[11] M☉
Radius0.25[8] R☉
C or Ac
Mass1.24[11] M☉
Luminosity2[9] L☉
Other designations
BD+49°1150, GC 5174, HD 26961, HR 1324, HIP 20070, SAO 24531
Database references
SIMBADdata
Light curves for b Persei. The top panel, plotted from TESS data,[12] shows the variability of the inner binary pair. The lower panels, plotted from AAVSO data,[13] show two eclipses.

In addition to the primary, an A-type giant, there is a smaller and cooler companion in a 1.53 day orbit, probably an F-class star around absolute magnitude 3.0, and a more distant companion (star C or Ac) in an orbit calculated to be 702 days long.[6] The close binary pair forms a rotating ellipsoidal variable with a 1.53 day period. Star C forms an Algol-type variable system with the close binary, showing both primary eclipses (when star C passes in front of the inner pair) and secondary eclipses (when the inner pair passes in front of star C).[14] Timings of the eclipses show a 705.4-day period.[9]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. Abt, Helmut A. (2009). "MK Classifications of Spectroscopic Binaries". The Astrophysical Journal Supplement. 180 (1): 117–18. Bibcode:2009ApJS..180..117A. doi:10.1088/0067-0049/180/1/117. S2CID 122811461.
  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. Vizier catalog entry
  5. Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institution for Science. Bibcode:1953GCRV..C......0W. LCCN 54001336.
  6. Hill, G.; Aikman, G. C. L.; Cowley, A. P.; Bolton, C. T.; Thomas, J. C. (1976). "The radio-flaring triple system B Per". The Astrophysical Journal. 208: 152. Bibcode:1976ApJ...208..152H. doi:10.1086/154590.
  7. ESA (1997). "The Hipparcos and Tycho Catalogues". VizieR On-line Data Catalog. 1239. Bibcode:1997yCat.1239....0E.
  8. Duerbeck, H. W.; Schettler, A. (1979). "Photometric and spectroscopic study of the ellipsoidal variable b Persei". Acta Astronomica. 29: 225. Bibcode:1979AcA....29..225D.
  9. "Alert Notice 791: Anticipated secondary eclipse of b Per centered on September 29 2022 UT". AAVSO. Retrieved 2022-09-15.
  10. Royer, F. (2007). "Rotational velocities of A-type stars. III. Velocity distributions". Astronomy and Astrophysics. 463 (2): 671–682. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224. S2CID 18475298.
  11. Tokovinin, Andrei (23 February 2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5. eISSN 1538-4365.
  12. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 14 September 2022.
  13. "Download Data". aavso.org. AAVSO. Retrieved 14 September 2022.
  14. "b Per". The International Variable Star Index. AAVSO. Retrieved 15 September 2022.
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