Astronomy:Vela X-1

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Short description: X-ray emission source in the constellation Vela
Vela X-1
A visual band light curve for GP Velorum, adapted from Tjemkes et al. (1986)[1]
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Vela
Right ascension  09h 02m 06.861s[2]
Declination −40° 33′ 16.90″[2]
Apparent magnitude (V) 6.87
Spectral type B0.5Ia
Apparent magnitude (B) 7.301
Apparent magnitude (V) 6.926
Apparent magnitude (J) 5.833±0.020
Apparent magnitude (H) 5.705±0.034
Apparent magnitude (K) 5.596±0.024
U−B color index −0.51[3]
B−V color index 0.50[3]
Variable type Complex[citation needed]
Proper motion (μ) RA: −4.822[2] mas/yr
Dec.: 9.282[2] mas/yr
Parallax (π)0.4962 ± 0.0152[2] mas
Distance6,600 ± 200 ly
(2,020 ± 60 pc)
Other designations
Supergiant component: GP Vel, HD 77581, SAO 220767, HIP 44368, CPD−40°3072, CD−40°4838;
X-ray component: 1XRS 09002-403, 1RXS J090207.0-403311, 4U 0900-40
Database references

Vela X-1 is a pulsing, eclipsing high-mass X-ray binary (HMXB) system, associated with the Uhuru source 4U 0900-40 and the supergiant star HD 77581. The X-ray emission of the neutron star is caused by the capture and accretion of matter from the stellar wind of the supergiant companion. Vela X-1 is the prototypical detached HMXB.[4]

The orbital period of the system is 8.964 days, with the neutron star being eclipsed for about two days of each orbit by HD 77581. It has been given the variable star designation GP Velorum, and it varies from visual magnitude 6.76 to 6.99.[5] The spin period of the neutron star is about 283 seconds, and gives rise to strong X-ray pulsations. The mass of the pulsar is estimated to be at least 1.88±0.13 solar masses.[6]


Long term monitoring of the spin period shows small random increases and decreases over time similar to a random walk.[7] The accreting matter causes the random spin period changes. However, a recent study has detected nearly periodic spin period reversals in Vela X-1 on long time-scales of about 5.9 years.[8]

See also


  1. Tjemkes, S. A.; Zuiderwijk, E. J.; van Paradijs, J. (January 1986). "Optical light curves of massive X-ray binaries". Astronomy and Astrophysics 154: 77–91. Bibcode1986A&A...154...77T. Retrieved 29 April 2022. 
  2. 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. 3.0 3.1 Klare, G.; Neckel, T. (1977). "UBV, Hβ and polarization measurements of 1660 southern OB stars". Astronomy and Astrophysics Supplement 27: 215. Bibcode1977A&AS...27..215K. 
  4. Mauche, C. W.; Liedahl, D. A.; Akiyama, S.; Plewa, T. (2007). "Hydrodynamic and Spectral Simulations of HMXB Winds". Progress of Theoretical Physics Supplement 169: 196–199. doi:10.1143/PTPS.169.196. Bibcode2007PThPS.169..196M. 
  5. "GP Vel". AAVSO. 
  6. Quaintrell, H. (2003). "The mass of the neutron star in Vela X-1 and tidally induced non-radial oscillations in GP Vel". Astronomy and Astrophysics 401: 313–324. doi:10.1051/0004-6361:20030120. Bibcode2003A&A...401..313Q. 
  7. Bildsten, L. (1997). "Observations of Accreting Pulsars". The Astrophysical Journal Supplement Series 113 (2): 367–408. doi:10.1086/313060. Bibcode1997ApJS..113..367B. 
  8. Chandra, A. D. (2021). "Detection of nearly periodic spin period reversals in Vela X-1 on long time-scales: inkling of solar-like cycle in the donor star?". Monthly Notices of the Royal Astronomical Society 508 (3): 4429–4442. doi:10.1093/mnras/stab2382. Bibcode2021MNRAS.508.4429C. 

External links

Coordinates: Sky map 09h 02m 06.860s, −40° 33′ 16.91″