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[17.32] Deep Crustal Heating, and a Lower Limit on the Number of Galactic X-ray Transients

E. F. Brown (University of Chicago), R. E. Rutledge (Caltech)

We review observations of the quiescent luminosities and mean outburst luminosities of all soft X-ray transients in low-mass X-ray binaries known to date. We estimate the mean outburst flux (averaged over a recurrence timescale) from RXTE/ASM data, where available, and assess the uncertainties arising from bolometric corrections and sparse sampling of outbursts. This allows us to evaluate the ratio of mean outburst flux to quiescent flux and compare it with that expected from heating in the deep crust of the neutron star. This knowledge is also necessary input for comparison of neutron star transients with cooling neutron stars to constrain the strength of neutrino emissivity from the core. From the number of observed transients and their expected duty cycle, we place a lower bound on the total number of galactic transients.

This work is supported by the Department of Energy under grant B341495 to the Center for Astrophysical Thermonuclear Flashes at the University of Chicago and by NASA through grant 5-28919.

Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.