V520 Persei

V520 Persei is a blue supergiant member of NGC 869, one of the Perseus Double Cluster open clusters. It is an irregular variable star.

V520 Per is the brightest star at the very centre of NGC 869, the left of the two clusters
V520 Persei

V520 Per in the cluster NGC 869, labelled as χ
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 2h 19m 04.45266s[1]
Declination 57° 08′ 07.7912″[1]
Apparent magnitude (V) 6.567[2] (6.52 - 6.67[3])
Characteristics
Spectral type B3 Ia[4]
U−B color index −0.346[2]
B−V color index +0.452[2]
Variable type IA[3]
Astrometry
Radial velocity (Rv)−43.40[5] km/s
Proper motion (μ) RA: −0.79[1] mas/yr
Dec.: −1.77[1] mas/yr
Parallax (π)−0.30 ± 0.68[1] mas
Distance2,200[6] pc
Absolute magnitude (MV)−7.1[7]
Details
Mass29.5[6] M☉
Radius40.8[6] R☉
Luminosity190,000[7] L☉
Surface gravity (log g)2.69[6] cgs
Temperature21,300[6] K
Rotation66[7]
Age14[6] Myr
Other designations
V520 Per, HD 14134, HIP 10805, BD+56°522, SAO 23178, WDS J02191+5708, 2MASS J02190444+5708078
Database references
SIMBADdata

V520 Persei is the brightest member of the Double Cluster at magnitude 6.55.[2] Two brighter stars in the same field are foreground objects. 7 Persei, sometimes considered to be the actual star χ Persei, is a yellow giant star, and HD 14443 is a white supergiant. Several other early B supergiants in NGC 869 are the most luminous members of the cluster, while NGC 884 contains several red supergiants.[2]

The Washington Double Star Catalog lists V520 Per as a double star about 15" from a 13th magnitude A0 companion which is another cluster member. There are dozens of other stars within an arc-minute, including several brighter than 10th magnitude and two 15th magnitude stars closer than the listed companion.[8] The Catalogue of Components of Double and Multiple Stars also lists a single companion, but it is an 11th magnitude star 29" away.[9]

The Hipparcos parallax is negative with a large margin of error, so does not constrain the distance except that it is clearly large However, V520 Per is a well-defined member of NGC 869 by location, proper motion, photometry, and spectroscopy, which places it at the same distance of around 7,000 light years.[6]

The type of variability is listed in the General Catalogue of Variable Stars as IA, indicating it is poorly studied with no clear period. The visual range is 6.52 - 6.67.[3] Statistical analysis of Hipparcos photometry suggests a possible period of 1.6 days, but the type variability is not clearly defined.[10]

V520 Persei is a supergiant with a spectral class of B3. It also shows some emission lines in its spectrum.[6] It has exhausted its core hydrogen and expanded into a more luminous star fusing hydrogen in a shell or helium in its core. It is over 100,000 times more luminous than the sun, although only thirty times its mass. Much of the luminosity arises from ultraviolet radiation created by the temperature of over 20,000 K.

V520 Per has been identified as one of Flamsteed's "missing stars", catalogue numbers created by Flamsteed but not actually associated with a current star in that constellation. It is described as being 61 Andromedae, although it is well outside the boundary of Andromeda and Flamsteed catalogued other nearby stars in Perseus, for example 7 Persei for χ Per itself.[11]

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.
  2. Slesnick, Catherine L.; Hillenbrand, Lynne A.; Massey, Philip (2002). "The Star Formation History and Mass Function of the Double Cluster h and χ Persei". The Astrophysical Journal. 576 (2): 880. arXiv:astro-ph/0205130. Bibcode:2002ApJ...576..880S. doi:10.1086/341865. S2CID 11463246.
  3. 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.
  4. Kraus, M.; Borges Fernandes, M.; Kubát, J. (2009). "Parameters of galactic early B supergiants. The influence of the wind on the interstellar extinction determination". Astronomy and Astrophysics. 499 (1): 291. Bibcode:2009A&A...499..291K. doi:10.1051/0004-6361/200810319.
  5. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data". Astronomy and Astrophysics. 430 (1): 165–186. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. ISSN 0004-6361. S2CID 17804304.
  6. Marsh Boyer, Amber N.; McSwain, M. Virginia; Aragona, Christina; Ou-Yang, Benjamin (2012). "Physical Properties of the B and Be Star Populations of h and χ Persei". The Astronomical Journal. 144 (6): 158. arXiv:1209.5771. Bibcode:2012AJ....144..158M. doi:10.1088/0004-6256/144/6/158. S2CID 118614141.
  7. Crowther, P. A.; Lennon, D. J.; Walborn, N. R. (2006). "Physical parameters and wind properties of galactic early B supergiants". Astronomy and Astrophysics. 446 (1): 279–293. arXiv:astro-ph/0509436. Bibcode:2006A&A...446..279C. doi:10.1051/0004-6361:20053685. S2CID 18815761.
  8. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  9. Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. De l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
  10. Lefèvre, L.; Marchenko, S. V.; Moffat, A. F. J.; Acker, A. (2009). "A systematic study of variability among OB-stars based on HIPPARCOS photometry". Astronomy and Astrophysics. 507 (2): 1141. Bibcode:2009A&A...507.1141L. doi:10.1051/0004-6361/200912304.
  11. Wagman, M. (1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy. 18 (3): 209–223. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305. S2CID 118445625.
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