Soft X-ray spectral FITS of Geminga with model neutron star atmospheres

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Abstract

view Abstract Citations (41) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Soft X-Ray Spectral FITS of Geminga with Model Neutron Star Atmospheres Meyer, R. D. ; Pavlov, G. G. ; Meszaros, P. Abstract The spectrum of the soft X-ray pulsar Geminga consists of two components, a softer one which can be interpreted as thermal-like radiation from the surface of the neutron star, and a harder one interpreted as radiation from a polar cap heated by relativistic particles. We have fitted the soft spectrum using a detailed magnetized hydrogen atmosphere model. The fitting parameters are the hydrogen column density, the effective temperature Teff, the gravitational redshift z, and the distance to radius ratio, for different values of the magnetic field B. The best fits for this model are obtained when B less than or approximately 1 x 1012 G and z lies on the upper boundary of the explored range (z = 0.45). The values of Teff approximately = (2-3) x 105 K are a factor of 2-3 times lower than the value of Teff obtained for blackbody fits with the same z. The lower Teff increases the compatibility with some proposed schemes for fast neutrino cooling of neutron stars (NSs) by the direct Urca process or by exotic matter, but conventional cooling cannot be excluded. The hydrogen atmosphere fits also imply a smaller distance to Geminga than that inferred from a blackbody fit. An accurate evaluation of the distance would require a better knowledge of the ROSAT Position Sensitive Proportional Counter (PSPC) response to the low-energy region of the incident spectrum. Our modeling of the soft component with a cooler magnetized atmosphere also implies that the hard-component fit requires a characteristic temperature which is higher (by a factor of approximately 2-3) and a surface area which is smaller (by a factor of 103, compared to previous blackbody fits. Publication: The Astrophysical Journal Pub Date: September 1994 DOI: 10.1086/174642 Bibcode: 1994ApJ...433..265M Keywords: Atmospheric Models; Neutron Stars; Pulsars; Stellar Atmospheres; Stellar Models; X Ray Astronomy; Mathematical Models; Neutrinos; Stellar Temperature; Astronomy; DENSE MATTER; STARS: PULSARS: INDIVIDUAL NAME: GEMINGA; STARS: ATMOSPHERES; STARS: NEUTRON full text sources ADS | data products SIMBAD (1) HEASARC (1)

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