Vela X-1
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Vela |
| Right ascension | 09h 02m 06.860s |
| Declination | −40° 33′ 16.91″ |
| Characteristics | |
| Spectral type | B0.5Ib |
| 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 |
| B−V color index | 0.50 |
| Variable type | Complex |
| Astrometry | |
| Proper motion (μ) | RA: −5.81 mas/yr Dec.: 8.25 mas/yr |
| Distance | 6200±650 ly (1900±200 pc) |
| Details | |
| Mass | 1.88 (neutron star), ~18 (supergiant) M☉ |
| Radius | ~11.2 R☉ |
| Luminosity | 112,000 (supergiant) L☉ |
| Temperature | 31,500 (supergiant) K |
| Metallicity | ? |
| Rotation | 8.964 days (supergiant) |
| Age | ? years |
| Other designations | |
| Data sources: | |
| [1], Hipparcos Catalogue, GCVS (4.2), [2],[3] |
|
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. 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.[5]
Characteristics
Long term monitoring of the spin period shows small random increases and decreases over time similar to a random walk.[6] The accreting matter causes the random spin period changes.
Note
Vela X-1 should not be confused with the isolated radio pulsar, Vela Pulsar, which is a very different kind of object. Vela is associated with a very strong 100 MeV gamma-ray source, which corresponds to a rather weak Uhuru X-ray source, 4U 0833-45.
See also
References
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Coordinates: 
09h 02m 06.860s, −40° 33′ 16.91″
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