Central Compact Objects in Supernova Remnants

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Central Compact Objects in Supernova Remnants , or CCOs for short, are point sources of X-rays close to the centers of supernova remnants . They are probably young neutron stars with an unusually weak magnetic field that were formed by a nuclear collapse supernova a few thousand years ago.

properties

The X-ray spectra of the Central Compact Objects in Supernova Remnants show a blackbody temperature of 0.2 to 0.5 keV with a luminosity of 10 33 to 10 34 erg / s. The diameter of the radiation source derived from this is 0.3 to 3 km if the X-rays are interpreted as thermal radiation . This value is considerably smaller than the typical diameter of a neutron star born in a nuclear collapse supernova, with a value of around 20 kilometers. If it is assumed that the atmosphere of the neutron stars mainly consists of carbon due to a previous accretion event, the radius is 10 to 12 km. The energy distribution of the X-rays can be interpreted by an atmosphere made of carbon. In the case of Cassiopeia A , a surprisingly rapid drop in temperature of one to two percent was observed within just 10 years.

The position of the CCOs is close to the centers of supernova remnants and the neutron stars could not be detected in the range of radio radiation or gamma radiation . They also do not lie within pulsar wind nebulae , in which a pulsar with high-energy particle radiation transports energy into the supernova remnant. It is therefore excluded that the CCOs are pulsars whose radiation cone is not directed towards the earth. From the expansion speed of the nebulae, the age of the supernova remnants with a compact central object is estimated to be a few thousand years with an upper limit of 20,000 years.

For some CCOs, the rotation period could be determined from a periodic variability of the X-ray radiation and is around 0.1 s. These values ​​are likely to be close to the original values ​​at the birth of the neutron stars. The period lengthening is small and, in contrast to pulsars, the radiated energy cannot arise from the decrease in rotation speed. The derived magnetic flux density of around 10 11 Gauss is orders of magnitude below that of normal pulsars. Because of the low magnetic field density, the CCOs are also referred to as anti- magnetars . The magnetic field density exceeds the values ​​for millisecond pulsars , but they rotate much faster. This confirms the assumption that the pulsar mechanism is not active in CCOs. The amplitude of the pulsed radiation reaches up to 64 percent in the case of PSR J1852 + 0040 and is likely to be caused by a different temperature distribution ( hot spots ) on the surface of the neutron stars. The characteristic age calculated from the slowing down of the rotation is orders of magnitude higher than the age derived from the expansion speed of the supernova remnant. It is therefore assumed that the CCOs were already born with their current density of the magnetic field.

Origin and development

Central Compact Objects in Supernova Remnants are born in core collapse supernovae and are young, between a few hundred to a thousand years old. In the supernova remnants within 5,000 parsecs in the age range up to 15,000 years, 14 pulsars, 5 CCOs and one unusual X-ray pulsar have been found. The CCOs are therefore a common result of the explosion of a massive star after its central energy resources have been depleted. However, the low magnetic flux density is difficult to interpret as the result of a supernova explosion. One hypothesis is therefore that the plasma that fell back on the neutron star buried the magnetic field in the crust temporarily. It is therefore conceivable that the magnetic field will reach the surface again by diffusion . After a few 10,000 years, the magnetic flux densities typical of pulsars could be reached and the neutron star reappears as a pulsating radio source. The different appearance of the CCOs is therefore probably a consequence of a different geometry of the magnetic field that has returned to the star's surface.

Examples

Central Compact Objects in Supernova Remnants have been identified in the following supernova remnants:

Individual evidence

  1. ↑ Alice K. Harding: The Neutron Star Zoo . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1302.0869v1 .
  2. ↑ KG Elshamouty et al .: Measuring the cooling of the neutron star in Cassiopeia A with all Chandra X-ray Observatory Detectors . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1306.3387v1 .
  3. ^ George G. Pavlov, Divas Sanwal & Marcus A. Teter: Central Compact Objects in Supernova Remnants . In: Astrophysics. Solar and Stellar Astrophysics . 2003, arxiv : astro-ph / 0311526v1 .
  4. ^ Andrea De Luca: Central Compact Objects in Supernova Remnants . In: Astrophysics. Solar and Stellar Astrophysics . 2007, arxiv : 0712.2209 .
  5. ^ EV Gotthelf, JP Halpern, and J. Alford: THE SPIN-DOWN OF PSR J0821–4300 AND PSR J1210–5226: CONFIRMATION OF CENTRAL COMPACT OBJECTS AS ANTI-MAGNETARS . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.2717 .
  6. ↑ D. Klochkov, G. Puehlhofer, V. Suleimanov, S. Simon, K. Werner, A. Santangelo: A non-pulsating neutron star in the supernova remnant HESS J1731-347 / G353.6-0.7 with a carbon atmosphere . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1307.1230v1 .
  7. ^ Wynn CG Ho: Central compact objects and their magnetic fields . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1210.7712 .
  8. ↑ Sandro Mereghetti: X-ray emission from isolated neutron stars . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1008.2891 .
  9. ^ Wynn CG Ho: Evolution of a buried magnetic field in the central compact object neutron stars . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1102.4870 .
  10. ^ Daniele Viganò, Jose A. Pons, Rosalba Perna: Central compact objects in magnetic lethargy . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1303.1997v1 .