Astronomy:Vela X-1

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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.[1]

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. 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.[2]


Long term monitoring of the spin period shows small random increases and decreases over time similar to a random walk.[3] The accreting matter causes the random spin period changes.

See also


  1. 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. 
  2. 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. 
  3. Bildsten, L. (1997). "Observations of Accreting Pulsars". The Astrophysical Journal Supplement Series 113 (2): 367–408. doi:10.1086/313060. Bibcode1997ApJS..113..367B. 

External links

Coordinates: Sky map 09h 02m 06.860s, −40° 33′ 16.91″ X-1 was the original source. Read more.