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We present a detailed observational and theoretical study of a ∼ 3 hr long X-ray burst (the " super burst ") observed by the Rossi X-ray Timing Explorer (RXTE) from the low mass X-ray binary (LMXB) 4U 1820-30. This is the longest X-ray burst ever observed from this source, and perhaps one of the longest ever observed in great detail from any source. We show(More)
We present an analytic calculation of the thermonuclear depletion of lithium in contracting, fully convective, pre-main sequence stars of mass M ∼ < 0.5M ⊙. Previous numerical work relies on still-uncertain physics (atmospheric opacities and convection, in particular) to calculate the effective temperature as a unique function of stellar mass. We assume(More)
Nuclear reactions occurring at densities ≈ 10 12 g cm −3 in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature ≈ (5–10) × 10 7 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot core, as if the neutron star were newly born. For the time-averaged accretion rates (∼(More)
We develop and calibrate a realistic model flame for hydrodynamical simulations of deflagrations in white dwarf (Type Ia) supernovae. Our flame model builds on the advection-diffusion-reaction model of Khokhlov and includes electron screening and Coulomb corrections to the equation of state in a self-consistent way. We calibrate this model flame—its(More)
The type-I X-ray bursting low mass X-ray binary KS 1731−260 was recently detected for the first time in quies-cence by Wijnands et al., following a τ outburst ≈13 yr outburst which ended in Feb 2001. We show that the emission area radius for a H atmosphere spectrum (possibly with a hard power-law component that dominates the emission above 3.5 keV) is(More)
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ABSTRACT The transient neutron star low-mass X-ray binary and 11 Hz X-ray(More)
In quasi-persistent neutron star transients, long outbursts cause the neutron star crust to be heated out of thermal equilibrium with the rest of the star. During quiescence, the crust then cools back down. Such crustal cooling has been observed in two quasi-persistent sources: KS 1731Ϫ260 and MXB 1659Ϫ29. Here we present an additional Chandra observation(More)
Neutron stars, with their strong surface gravity, have interestingly short timescales for the sedi-mentation of heavy elements. Motivated by observations of Type I X-ray bursts from sources with extremely low persistent accretion luminosities, L X < 10 36 ergs s −1 (≃ 0.01L Edd), we study how sed-imentation affects the distribution of isotopes and the(More)
Using the Chandra/ACIS-I detector, we have identified an X-ray source (CXOU 132619.7-472910.8) in the globular cluster NGC 5139 with a thermal spectrum identical to that observed from transiently accreting neutron stars in quiescence. The absence of intensity variability on timescales as short as 4 seconds (< 25% rms variability) and as long as 5 years(More)