Ignition column depths of helium-rich thermonuclear bursts from 4U 1728-34 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: We analysed thermonuclear type-I X-ray bursts observed from the low-massX-ray binary 4U1728-34 by RXTE, Chandra and INTEGRAL. We compared the variationin burst energy and recurrence times as a function of accretion rate with thepredictions of a numerical ignition model including a treatment of the heatingand cooling in the crust. We found that the measured burst ignition columndepths are significantly below the theoretically predicted values, regardlessof the assumed thermal structure of the neutron star interior. While it ispossible that the accretion rate measured by Chandra is underestimated, due toadditional persistent spectral components outside the sensitivity band, therequired correction factor is typically 3.6 and as high as 6, which isimplausible. Furthermore, such underestimation is even more unlikely for RXTEand INTEGRAL, which have much broader bandpasses. Possible explanations for theobserved discrepancy include shear-triggered mixing of the accreted helium tolarger column depths, resulting in earlier ignition, or the fractional coveringof the accreted fuel on the neutron star surface.



Autor: Zdenka Misanovic, Duncan K. Galloway, Randall L. Cooper

Fuente: https://arxiv.org/







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