Crab Pulsar
 The Crab Pulsar. Image combines optical data from Hubble (in red) and X-ray images from Chandra (in blue). | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 05h 34m 31.97s |
| Declination | +22° 00' 52.1"' |
| Apparent magnitude (V) | 16.5 |
| Characteristics | |
| Spectral type | F |
| U−B color index | -0.45 |
| B−V color index | +0.5 |
| Variable type | None |
| Astrometry | |
| Radial velocity (Rv) | 0.0 km/s |
| Proper motion (μ) | RA: 0.0 mas/yr Dec.: 0.0 mas/yr |
| Parallax (π) | 7.0 ± 10.0 mas |
| Distance | 6500 ly (2000 pc) |
| Absolute magnitude (MV) | ? |
| Details | |
| Mass | ? M☉ |
| Radius | ? R☉ |
| Luminosity | ? L☉ |
| Temperature | ? K |
| Metallicity | ? |
| Rotation | 1800 rpm |
| Age | ? years |
| Other designations | |
SNR G184.6-05.8, PULS NP 0531, 3A 0531+219, NAME CRABE, AJG 1, 1ES 0532+21.5, NAME CRAB NEBULA, 2C 481, GeV J0534+2159, NAME CRAB SN, SN 1054, 3C 144.0, GRS 184.60 -05.80, NAME CRAB NEB SN 1054A, 3C 144, NAME CRAB PSR, 2U 0531+22, 4C 21.19, H 0531+219, NGC 1952, 3U 0531+21, 1CG 185-05, NOVA Tau 1054, 4U 0531+21, V* CM Tau, NRL 2, VRO 21.05.01, PKS 0531+219, W 9, CTA 36, LBN 184.62-05.65, PLX 1266, X Tau XR-1, CTB 18, LBN 833, PSR 0531, X Tau X-1, Cul 0531+219, PSR B0531+21, Cul 0531+21, Mills 05+2A, PSR 0532, DA 179, M 1, PSR B0532+21, NAME TAU A, PSR J0534+2200, NAME CRAB PULSAR, PSR B0531+21.9, NAME TAURUS A, PULS NP 0532. | |
The Crab Pulsar (PSR B0531+21 or PSR J0534+2200) is a relatively young neutron star located in the Crab Nebula. The optical pulsar is roughly 25 km in diameter and the pulsar "beams" rotate once every 33 milliseconds, or 30 times each second. The outflowing relativistic wind from the neutron star generates synchrotron emission, which produces the bulk of the emission from the nebula, seen from radio waves through to gamma rays. The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the surrounding nebula, forming a termination shock. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar into the main body of the nebula. The period of the pulsar's rotation is slowing by 38 nanoseconds per day due to the large amounts of energy carried away in the pulsar wind.[1]
The Crab Nebula is often used as a calibration source in X-ray astronomy. It is very bright in X-rays and the flux density and spectrum are known to be constant, with the exception of the pulsar itself. The pulsar provides a strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, 'crab' and 'millicrab' are sometimes used as units of flux density. A millicrab corresponds to a flux density of about 2.4x10-11 erg s-1 cm−2 (2.4x10-14 W m−2) in the 2–10 keV X-ray band, for a "crab-like" X-ray spectrum, which is roughly a powerlaw in photon energy, I(E)=9.5 E-1.1. Very few X-ray sources ever exceed one crab in brightness.
History
The modern history of the crab pulsar begins with the identification of the central star of the nebula in optical light. Focus was made on two stars near the center of the nebula (referred to in the literature as the "north following" and "south preceding" stars). In September 1942, Walter Baade rules out the north following star but finds the evidence inconclusive for the south preceding.[2] Rudolf Minkowski, in the same issue of Astrophysical Journal as Baade, advances spectral arguments claiming the "evidence admits, but does not prove, the conclusion that the south preceding star is the central star of the nebula".[3]
In late 1968, David H. Staelin and Edward C. Reifenstein III reported the discovery of two pulsating radio sources "near the crab nebula that could be coincident with it" using the 300-foot Green Bank radio antenna.[4] They were given the designations NP 0527 and NP 0532. A subsequent study by them including William D. Brundate found that the NP 0532 source is located at the Crab Nebula.[5] A radio source was also reported coincident with the crab nebula in late 1968 by L. I. Matveenko in Soviet Astronomy.[6]
Optical pulsations were reported by Nather, Warner, and Macfarlane in February of 1969.[7]
References
- ^ Supernovae, Neutron Stars & Pulsars
- ^ Baade, Walter (September 1942), "The Crab Nebula", Astrophysical Journal, 96: 188–198
{{citation}}: External link in|author-link= - ^
Minkowski, Rudolf (September 1942), "The Crab Nebula", Astrophysical Journal, 96: 199–213
{{citation}}: External link in|author-link= - ^ Staelin, David H.; Reifenstein, III, Edward C. (December 1968), "Pulsating radio sources near the Crab Nebula", Science, 162: 1481–1483
{{citation}}: External link in|author-link=and|author2-link= - ^ Reifenstein, III, Edward C.; Staelin, David H.; Brundage, William D. (1969), "Crab Nebula Pulsar NPO527", Phys. Rev. Lett., 22 (7): 311–311, doi:10.1103/PhysRevLett.22.311
{{citation}}: External link in|author-link=and|author2-link= - ^ Matveenko, L. I. (Nov–Dec 1968), "Position of a Source of Small Angular Size in the Crab Nebula", Soviet Astronomy, 12: 552–553
{{citation}}: CS1 maint: date and year (link) CS1 maint: date format (link) - ^ Nather, R. E.; Warner, B.; Macfarlane, M. (February 08, 1969), "Optical Pulsations in the Crab Nebula Pulsar", Nature, 221: 527–527
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