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تسجيل مستخدم جديدThe Soft X-ray Spectrum of the High Mass X-Ray Binary V0332+53 in Quiescence
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The propeller effect should cut off accretion in fast-spinning neutron star high mass X-ray binaries (HMXBs) at low mass transfer rates. However, accretion continues in some HMXBs at $L_{x} < 10^{34}$ erg s$^{-1}$, as evidenced by continuing pulsations. Indications of spectral softening in systems in the propeller regime suggest that some HMXBs are undergoing fundamental changes in their accretion regime. A 39 ks textit{XMM-Newton} observation of the transient HMXB V0332+53 found it at a very low X-ray luminosity ($L_{x} sim 4times 10^{32}$ erg s${^{-1}}$). A power-law spectral fit requires an unusually soft spectral index ($4.4^{+0.9}_{-0.6}$), while a magnetized neutron star atmosphere model, with temperature lt 6.7$pm 0.2$ K and inferred emitting radius of $sim0.2-0.3$ km, gives a good fit. We suggest that the quiescent X-ray emission from V0332+53 is mainly from a hot spot on the surface of the neutron star. We could not detect pulsations from V0332+53, due to the low count rate. Due to the high $N_H$, thermal emission from the rest of the neutron star could be only weakly constrained, to lt $<$6.14$^{+0.05}_{-6.14}$ K, or $<3times10^{33}$ erg s${^{-1}}$.
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