Astronomy:Crab Pulsar

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Short description: Pulsar in the constellation Taurus
Crab Pulsar
Chandra-crab.jpg
The Crab Nebula, which contains the Crab Pulsar (the red star in the center). Image combines optical data from Hubble (in red) and X-ray images from Chandra (in blue).
Credit: NASA/CXC/ASU/J. Hester et al.[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Taurus
Right ascension  05h 34m 31.95s[2]
Declination +22° 00′ 52.2″[2]
Characteristics
Evolutionary stage Neutron star
Astrometry
Proper motion (μ) RA: −11.34 ± 0.06[3] mas/yr
Dec.: 2.65 ± 0.14[3] mas/yr
Parallax (π)0.53 ± 0.06[3] mas
Distanceapprox. 6,200 ly
(approx. 1,900 pc)
Details
Luminosity0.9 L☉
Temperaturecenter (modeled): ~3×108[4] K,
surface: ~1.6×106 K
Rotation33.5028583 ms[5]
Other designations
SNR G184.6-05.8, 2C 481, 3C 144.0, SN 1054A, 4C 21.19, NGC 1952, PKS 0531+219, PSR B0531+21, PSR J0534+2200, CM Tau
Database references
SIMBADdata

The Crab Pulsar (PSR B0531+21 or Baade's Star) is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054.[6][7][8] Discovered in 1968, the pulsar was the first to be connected with a supernova remnant.[9]

The sky seen in gamma-rays as seen by the Fermi Gamma-ray Space Telescope, reveals the Crab Pulsar as one of the brightest gamma-ray sources in the sky.

The Crab Pulsar is one of very few pulsars to be identified optically. The optical pulsar is roughly 20 kilometres (12 mi) in diameter and has a rotational period of about 33 milliseconds, that is, the pulsar "beams" perform about 30 revolutions per second.[4] 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 increasing by 38 nanoseconds per day due to the large amounts of energy carried away in the pulsar wind.[10]

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 2.4×10−11 erg s−1 cm−2 (2.4×10−14 W/m2) in the 2–10 keV X-ray band, for a "crab-like" X-ray spectrum, which is roughly power-law in photon energy: I ~ E−1.1.[citation needed] Very few X-ray sources ever exceed one crab in brightness.

Pulsed emission up to 1.5 TeV has been detected from the Crab pulsar[11] and together with the Vela pulsar at 20 TeV are the only two known pulsar with emission in this energy range[12]

History of observation

X-ray picture of Crab Nebula, taken by Chandra

The Crab Nebula was identified as the remnant of SN 1054 by 1939. Astronomers then searched for the nebula's central star. There were two candidates, referred to in the literature as the "north following" and "south preceding" stars. In September 1942, Walter Baade ruled out the "north following" star, but found the evidence inconclusive for the "south preceding" star.[13] Rudolf Minkowski, in the same issue of The Astrophysical Journal as Baade, advanced spectral arguments claiming that the "evidence admits, but does not prove, the conclusion that the south preceding star is the central star of the nebula".[14]

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 (91 m) Green Bank radio antenna.[15] They were given the designations NP 0527 and NP 0532. The period and location of the Crab Nebula pulsar NP 0532 was discovered by Richard V. E. Lovelace and collaborators on November 10, 1968, at the Arecibo radio observatory.[16]

A subsequent study by them, including William D. Brundage, also found that the NP 0532 source is located at the Crab Nebula.[17] A radio source was also reported coincident with the Crab Nebula in late 1968 by L. I. Matveenko in Soviet Astronomy.[18]

Optical pulsations were first reported by Cocke, Disney, and Taylor using the 36-inch (91 cm) telescope on Kitt Peak of the Steward Observatory of the University of Arizona.[19] Their discovery was confirmed by Nather, Warner, and Macfarlane.[20]

Light curve and slow motion picture of the pulsar located in the center of the Crab Nebula. Image taken with a photon counting camera on the 80cm telescope of the Wendelstein Observatory, Dr. F. Fleischmann, 1998

Jocelyn Bell Burnell, who co-discovered the first pulsar PSR B1919+21 in 1967, relates that in the late 1950s a woman viewed the Crab Nebula source at the University of Chicago's telescope, then open to the public, and noted that it appeared to be flashing. The astronomer she spoke to, Elliot Moore, disregarded the effect as scintillation, despite the woman's protestation that as a qualified pilot she understood scintillation and this was something else. Bell Burnell notes that the 30 Hz frequency of the Crab Nebula optical pulsar is difficult for many people to see.[21][22]

In 2007, it was reported that Charles Schisler detected a celestial source of radio emission in 1967 at the location of the Crab Nebula, using a United States Air Force in Alaska designed as an early warning system to detect intercontinental ballistic missiles. This source was later understood by Schisler to be the Crab Pulsar, after the news of Bell Burnell's initial pulsar discoveries was reported.[21] However, Schisler's detection was not reported publicly for four decades due to the classified nature of the radar observations.[23]

The Crab Pulsar was the first pulsar for which the spin-down limit was broken using several months of data of the LIGO observatory. Most pulsars do not rotate at constant rotation frequency, but can be observed to slow down at a very slow rate (3.7×10−10 Hz/s in case of the Crab). This spin-down can be explained as a loss of rotation energy due to various mechanisms. The spin-down limit is a theoretical upper limit of the amplitude of gravitational waves that a pulsar can emit, assuming that all the losses in energy are converted to gravitational waves. No gravitational waves observed at the expected amplitude and frequency (after correcting for the expected Doppler shift) proves that other mechanisms must be responsible for the loss in energy. The non-observation so far is not totally unexpected, since physical models of the rotational symmetry of pulsars puts a more realistic upper limit on the amplitude of gravitational waves several orders of magnitude below the spin-down limit. It is hoped that with the improvement of the sensitivity of gravitational wave instruments and the use of longer stretches of data, gravitational waves emitted by pulsars will be observed in future.[24] The only other pulsar for which the spin-down limit was broken so far is the Vela Pulsar.

A slow-motion animation of the Crab Pulsar taken at 800 nm wavelength (near-infrared) using a Lucky Imaging camera from Cambridge University, showing the bright pulse and fainter interpulse.

In 2019 the Crab Nebula, and presumably therefore the Crab Pulsar, was observed to emit gamma rays in excess of 100 TeV, making it the first identified source of ultra-high-energy cosmic rays.[25]

In 2023, Very long baseline interferometry (VLBI) was used to conduct precision astrometry using the radio giant-pulse emission of the Crab Pulsar, thus measuring a precise distance to the Crab Pulsar.[3]

References

  1. ↑ "Space Movie Reveals Shocking Secrets of the Crab Pulsar" (Press release). NASA. September 19, 2002.
  2. ↑ 2.0 2.1 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 3.2 3.3 Lin, Rebecca; van Kerkwijk, Marten H.; Kirsten, Franz; Pen, Ue-Li; Deller, Adam T. (1 August 2023). "The Radio Parallax of the Crab Pulsar: A First VLBI Measurement Calibrated with Giant Pulses". The Astrophysical Journal 952 (2): 161. doi:10.3847/1538-4357/acdc98. Bibcode: 2023ApJ...952..161L. 
  4. ↑ 4.0 4.1 Becker, W.; Aschenbach, B. (1995). "ROSAT HRI Observations of the Crab Pulsar An Improved Temperature Upper Limit for PSR 0531+21". The Lives of the Neutron Stars. 450. Kluwer Academic. p. 47. ISBN 978-0-7923-324-6-6. Bibcode: 1995ASIC..450...47B. 
  5. ↑ ATNF Pulsar Catalogue database entry. See Manchester, R. N. (2005), "The Australia Telescope National Facility Pulsar Catalogue", Astronomical Journal 129 (4): 1993–2006, doi:10.1086/428488, Bibcode: 2005AJ....129.1993M 
  6. ↑ Supernova 1054 – Creation of the Crab Nebula.
  7. ↑ Duyvendak, J. J. L. (1942), "Further Data Bearing on the Identification of the Crab Nebula with the Supernova of 1054 A.D. Part I. The Ancient Oriental Chronicles", Publications of the Astronomical Society of the Pacific 54 (318): 91, doi:10.1086/125409, Bibcode: 1942PASP...54...91D 
    Mayall, N. U.; Oort, Jan Hendrik (1942), "Further Data Bearing on the Identification of the Crab Nebula with the Supernova of 1054 A.D. Part II. The Astronomical Aspects", Publications of the Astronomical Society of the Pacific 54 (318): 95, doi:10.1086/125410, Bibcode: 1942PASP...54...95M 
  8. ↑ Brandt, K. (1983), "Ancient records and the Crab Nebula supernova", The Observatory 103: 106, Bibcode: 1983Obs...103..106B 
  9. ↑ Zeilik, Michael; Gregory, Stephen A. (1998), Introductory Astronomy & Astrophysics (4th ed.), Saunders College Publishing, p. 369, ISBN 978-0-03-006228-5 
  10. ↑ Supernovae, Neutron Stars & Pulsars.
  11. ↑ The H.E.S.S. Collaboration et al. (2023-10-05). "Discovery of a radiation component from the Vela pulsar reaching 20 teraelectronvolts" (in en). Nature Astronomy. doi:10.1038/s41550-023-02052-3. ISSN 2397-3366. https://www.nature.com/articles/s41550-023-02052-3. 
  12. ↑ The H.E.S.S. Collaboration; Aharonian, F.; Benkhali, F. Ait; Aschersleben, J.; Ashkar, H.; Backes, M.; Martins, V. Barbosa; Batzofin, R. et al. (2023-10-05). "Discovery of a radiation component from the Vela pulsar reaching 20 teraelectronvolts" (in en). Nature Astronomy. doi:10.1038/s41550-023-02052-3. ISSN 2397-3366. https://www.nature.com/articles/s41550-023-02052-3. 
  13. ↑ Baade, Walter (1942), "The Crab Nebula", Astrophysical Journal 96: 188, doi:10.1086/144446, Bibcode: 1942ApJ....96..188B 
  14. ↑ Minkowski, Rudolf (1942), "The Crab Nebula", Astrophysical Journal 96: 199, doi:10.1086/144447, Bibcode: 1942ApJ....96..199M 
  15. ↑ Staelin, David H.; Reifenstein, III, Edward C. (1968), "Pulsating radio sources near the Crab Nebula", Science 162 (3861): 1481–3, doi:10.1126/science.162.3861.1481, PMID 17739779, Bibcode: 1968Sci...162.1481S 
  16. ↑ IAU Circ. No. 2113, 1968.
  17. ↑ Reifenstein, III, Edward C.; Staelin, David H.; Brundage, William D. (1969), "Crab Nebula Pulsar NPO527", Physical Review Letters 22 (7): 311, doi:10.1103/PhysRevLett.22.311, Bibcode: 1969PhRvL..22..311R 
  18. ↑ Matveenko, L. I. (1968), "Position of a Source of Small Angular Size in the Crab Nebula", Soviet Astronomy 12: 552, Bibcode: 1968SvA....12..552M 
  19. ↑ Cocke, W. J.; Disney, M.; Taylor, D. J. (1969), "Discovery of Optical Signals from Pulsar NP 0532", Nature 221 (5180): 525, doi:10.1038/221525a0, Bibcode: 1969Natur.221..525C 
  20. ↑ Nather, R. E.; Warner, B.; Macfarlane, M. (1969), "Optical Pulsations in the Crab Nebula Pulsar", Nature 221 (5180): 527, doi:10.1038/221527a0, Bibcode: 1969Natur.221..527N 
  21. ↑ 21.0 21.1 Brumfiel (2007), "Air force had early warning of pulsars", Nature 448 (7157): 974–975, doi:10.1038/448974a, PMID 17728726, Bibcode: 2007Natur.448..974B 
  22. ↑ "Beautiful Minds: Jocelyn Bell Burnell", BBC television documentary broadcast 7 April 2010.
  23. ↑ Schisler, Charles (2008). "An Independent 1967 Discovery of Pulsars". AIP Conference Proceedings 983: 642–645. doi:10.1063/1.2900320. Bibcode: 2008AIPC..983..642S. https://pubs.aip.org/aip/acp/article/983/1/642/620966/An-Independent-1967-Discovery-of-Pulsars. 
  24. ↑ The LIGO Scientific Collaboration; Abbott, B.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amin, R. et al. (2008), "Beating the spin-down limit on gravitational wave emission from the Crab pulsar", Astrophys. J. 683 (1): L45–L50, doi:10.1086/591526, Bibcode: 2008ApJ...683L..45A 
    And erratum in Abbott, B. et al. (2009), "none", Astrophys. J. 706 (1): L203–L204, doi:10.1088/0004-637X/706/1/L203, Bibcode: 2009ApJ...706L.203A 
  25. ↑ Amenomori, M. (13 June 2019). "First detection of photons with energy beyond 100 TeV from an astrophysical source". Phys. Rev. Lett. 123 (5): 051101. doi:10.1103/PhysRevLett.123.051101. PMID 31491288. Bibcode: 2019PhRvL.123e1101A. https://inspirehep.net/record/1739844?ln=en. Retrieved 8 July 2019. 



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