Constraints on Thermal X‐Ray Radiation from SAX J1808.4−3658 and Implications for Neutron Star Neutrino Emission
Citations Over TimeTop 10% of 2007 papers
Abstract
Thermal X-ray radiation from neutron star soft X-ray transients in quiescence provides the strongest constraints on the cooling rates of neutron stars and thus on the interior composition and properties of matter in the cores of neutron stars. We analyze new (2006) and archival (2001) XMM-Newton observations of the accreting millisecond pulsar SAX J1808.43658 in quiescence, which provide the most stringent constraints to date. The X-ray spectrum of SAX J1808.43658 in the 2006 observation is consistent with a power law of photon index 1:83 AE 0:17, without requiring the presence of a blackbody-like component from a neutron star atmosphere. Our 2006 observation shows a slightly lower 0.5Y10 keV X-ray luminosity, at a level of 68 15 13 % of that inferred from the 2001 observation. Simultaneous fitting of all available XMM-Newton data allows a constraint on the quiescent neutron star (0.01Y10 keV) luminosity of L NS < 1:1 ; 10 31 ergs s 1 . This limit excludes some current models of neutrino emission mediated by pion condensates and provides further evidence of additional cooling processes, such as neutrino emission via direct Urca processes involving nucleons and /or hyperons, in the cores of massive neutron stars.
Related Papers
- Handbook of Pulsar Astronomy(2004)
- → Selection of radio pulsar candidates using artificial neural networks(2010)122 cited
- → The Parkes multibeam pulsar survey - IV. Discovery of 180 pulsars and parameters for 281 previously known pulsars(2004)184 cited
- Pulsars as physics laboratories(1993)
- → Pulsar interpulses and other off-pulse emission(1977)4 cited