The Compact Central Object in Cassiopeia A: A Neutron Star with Hot Polar Caps or a Black Hole?
| العنوان: | The Compact Central Object in Cassiopeia A: A Neutron Star with Hot Polar Caps or a Black Hole? |
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| المؤلفون: | George G. Pavlov, V. E. Zavlin, Bernd Aschenbach, Joachim E. Truemper, Divas Sanwal |
| المصدر: | The Astrophysical Journal. 531:L53-L56 |
| بيانات النشر: | American Astronomical Society, 2000. |
| سنة النشر: | 2000 |
| مصطلحات موضوعية: | Physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Compact star, Redshift, Luminosity, Black hole, Neutron star, Pulsar, Space and Planetary Science, ROSAT, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Supernova remnant, Astrophysics::Galaxy Astrophysics |
| الوصف: | The central pointlike X-ray source of the Cas A supernova remnant was discovered in the Chandra First Light Observation and found later in the archival ROSAT and Einstein images. The analysis of these data does not show statistically significant variability of the source. The power-law fit yields the photon index 2.6-4.1, and luminosity (2-60)e34 erg/s, for d=3.4 kpc. The power-law index is higher, and the luminosity lower, than those observed fromvery young pulsars. One can fit the spectrum equally well with a blackbody model with T=6-8 MK, R=0.2-0.5 km, L=(1.4-1.9)e33 erg/s. The inferred radii are too small, and the temperatures too high, for the radiationcould be interpreted as emitted from the whole surface of a uniformly heated neutron star. Fits with the neutron star atmosphere models increase the radius and reduce the temperature, but these parameters are still substantially different from those expected for a young neutron star. One cannot exclude, however, that the observed emission originates from hot spots on a cooler neutron star surface. Because of strong interstellar absorption, the possible low-temperature component gives a small contribution to the observed spectrum; an upper limit on the (gravitationally redshifted) surface temperature is < 1.9-2.3 MK. Amongst several possible interpretations, we favor a model of a strongly magnetized neutron star with magnetically confined hydrogen or helium polar caps on a cooler iron surface. Alternatively, the observed radiation may be interpreted as emitted by a compact object (more likely, a black hole) accreting from a fossil disk or from a late-type dwarf in a close binary. 12 pages, 2 figures, submitted to ApJL |
| تدمد: | 0004-637X |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::aa6a79fb8f5b10de081e41b551abccf5 https://doi.org/10.1086/312521 |
| حقوق: | OPEN |
| رقم الأكسشن: | edsair.doi.dedup.....aa6a79fb8f5b10de081e41b551abccf5 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 0004637X |
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