Figure 83

Figure 83: X-ray luminosities of SXTs in quiescence vs. time-averaged accretion rates. The heating curves correspond to different neutron star masses, increasing from the top to the bottom, with a step of ΔM = 0.02M ⊙. The EoS of the core is moderately stiff, with Mmax = 1.977 M ⊙ [340]. The model of a strong proton and a weak neutron superfluidity is assumed [261]. The highest curve (hottest stars) corresponds to M = M ⊙, and the lowest one (coldest stars) to M = Mmax. The upper bundle of coalescing curves corresponds to masses M ⊙ ≤ M ≤ MD, where a star of mass M D has a central density equal to the threshold for the direct Urca process. The red dotted line represents thermal states of a “basic model” (nonsuperfluid core, slow cooling via a modified Urca process). Total deep heat released per accreted nucleon is Qtot = 1.5 MeV. Figure made by K.P. Levenfish. For a further description of neutron star models and observational data see Levenfish & Haensel [261].