X Persei

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X Persei
Perseus constellation map.svg
Red circle.svg

Location of X Per (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Perseus
Right ascension 03h 55m 23.0778s[1]
Declination +31° 02′ 45.038″[1]
Apparent magnitude (V) 6.778[2] (6.03 - 7.00[3])
Spectral type O9.5IIIe-B0Ve[4]
U−B color index −0.790[2]
B−V color index +0.137[2]
Variable type γ Cas + X-ray pulsar[3]
Radial velocity (Rv) −50.00[5] km/s
Proper motion (μ) RA: −1.330[1] mas/yr
Dec.: −1.743[1] mas/yr
Parallax (π) 1.38 ± 0.48[1] mas
Distance 950[6] pc
Absolute magnitude (MV) −3.47[2]
Primary X Per
Companion 4U 0352+309
Period (P) 250.3 days
Semi-major axis (a) 2.2 AU
Eccentricity (e) 0.111
Inclination (i) 23 - 30°
Mass 15.5[8] M
Radius 6.5[8] R
Luminosity 29,000[2] L
Surface gravity (log g) 4.0[2] cgs
Temperature 29,500[8] K
Rotational velocity (v sin i) 215[2] km/s
Age 5[2] Myr
Other designations
X Persei, HR 1209, HIP 18350, HD 24534, BD+30°591, WDS J03554+3103, AAVSO 0349+30
A: X Per
B: 4U 0352+309
Database references

X Persei is a high-mass X-ray binary system located in the constellation Perseus, approximately 950 parsecs away.

The optical star X Persei has been classified either as an O-type giant or a B-type main sequence star. It is a Be star, rotating rapidly, and at times surrounded by a disk of expelled material. This qualifies it as a Gamma Cassiopeiae variable, and the visual range is magnitude 6 - 7. In 1989 and 1990, the spectrum of X Persei changed from a Be star to a normal B class star while it faded significantly. This appears to have been caused by the loss of the accretion disk. The disk has since reformed and shows strong emission lines.[9]

X Persei is in orbit with a neutron star, which is catalogued as 4U 0352+309 in the final Uhuru catalog of X-ray objects. It is a pulsar with an unusually long period of 837 seconds.[7] The pulsar has shown period changes that are associated with mass transfer from the more massive primary star. Between 1973 and 1979 it was seen to increase its rate of spin, associated with a strong x-ray flare and presumed strong mass transfer. Since then the spin has been slowing despite small x-ray flares.[9]

The combination of a neutron star and OB emission line star places X Persei in the Be/X-ray binary class of stars.[9]

There is a faint optical companion separated by 22.5" which the Catalog of Components of Double and Multiple Stars refers to as X Persei B.[10]


  1. ^ a b c d e Gaia Collaboration; Brown, A. G. A; Vallenari, A; Prusti, T; De Bruijne, J. H. J; Mignard, F; Drimmel, R; Babusiaux, C; Bailer-Jones, C. A. L; Bastian, U; Biermann, M; Evans, D. W; Eyer, L; Jansen, F; Jordi, C; Katz, D; Klioner, S. A; Lammers, U; Lindegren, L; Luri, X; O'Mullane, W; Panem, C; Pourbaix, D; Randich, S; Sartoretti, P; Siddiqui, H. I; Soubiran, C; Valette, V; Van Leeuwen, F; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy & Astrophysics. 595: A2. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. 
  2. ^ a b c d e f g h Lyubimkov, L. S.; Rostopchin, S. I.; Roche, P.; Tarasov, A. E. (1997). "Fundamental parameters, helium abundance and distance of X Persei". Monthly Notices of the Royal Astronomical Society. 286 (3): 549. Bibcode:1997MNRAS.286..549L. doi:10.1093/mnras/286.3.549. 
  3. ^ a b 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. ^ Valencic, Lynne A.; Smith, Randall K. (2013). "Interstellar Abundances toward X Per, Revisited". The Astrophysical Journal. 770: 22. Bibcode:2013ApJ...770...22V. doi:10.1088/0004-637X/770/1/22. 
  5. ^ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878Freely accessible. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. 
  6. ^ Walter, Roland; Lutovinov, Alexander A.; Bozzo, Enrico; Tsygankov, Sergey S. (2015). "High-mass X-ray binaries in the Milky Way. A closer look with INTEGRAL". The Astronomy and Astrophysics Review. 23: 2. arXiv:1505.03651Freely accessible. Bibcode:2015A&ARv..23....2W. doi:10.1007/s00159-015-0082-6. 
  7. ^ a b Delgado‐Marti, H.; Levine, A. M.; Pfahl, E.; Rappaport, S. A. (2001). "The Orbit of X Persei and Its Neutron Star Companion". The Astrophysical Journal. 546: 455. arXiv:astro-ph/0004258Freely accessible. Bibcode:2001ApJ...546..455D. doi:10.1086/318236. 
  8. ^ a b c Grundstrom, E. D.; Boyajian, T. S.; Finch, C.; Gies, D. R.; Huang, W.; McSwain, M. V.; O'Brien, D. P.; Riddle, R. L.; Trippe, M. L.; Williams, S. J.; Wingert, D. W.; Zaballa, R. A. (2007). "Joint Hα and X-Ray Observations of Massive X-Ray Binaries. III. The Be X-Ray Binaries HDE 245770 = A0535+26 and X Persei". The Astrophysical Journal. 660 (2): 1398. arXiv:astro-ph/0702283Freely accessible. Bibcode:2007ApJ...660.1398G. doi:10.1086/514325. 
  9. ^ a b c Li, Hui; Yan, Jingzhi; Zhou, Jianeng; Liu, Qingzhong (2014). "Long-term Optical Observations of the Be/X-Ray Binary X Per". The Astronomical Journal. 148 (6): 113. arXiv:1408.3542Freely accessible. Bibcode:2014AJ....148..113L. doi:10.1088/0004-6256/148/6/113. 
  10. ^ 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.