Paper: astro-ph/0509758
Date: Mon, 26 Sep 2005 16:01:18 GMT (156kb)

Title: The Rates of type I X-ray Bursts from Transients Observed with RXTE:
Evidence for Black Hole Event Horizons

Authors: Ronald A. Remillard (1), Dacheng Lin (1), Randall L.Cooper (2), and
Ramesh Narayan (2) ((1) MIT Kavli Institute for Astrophysics and Space
Research, and (2) Harvard-Smithsonian Center for Astrophysics)

Categories: astro-ph

Comments: 20 pages, 8 figures, submitted to ApJ
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We measure the rates of type I X-ray bursts from a likely complete sample of
37 non-pulsing Galactic X-ray transients observed with the RXTE ASM during
1996-2004. Our strategy is to test the prevailing paradigms for these sources,
which are well-categorized in the literature as either neutron-star systems or
black hole candidates. We measure burst rates as a function of the bolometric
luminosity. We find 135 type I bursts in 3.7 Ms of PCA light curves for the
neutron-star group, and the burst rate function is generally consistent with
our model predictions for bursts from accreting neutron stars. On the other
hand, none of the (20) bursts candidates passed spectral criteria for type I
bursts in 6.5 Ms of PCA light curves for black-hole binaries and candidates.
The burst function upper limits are compared to predictions of the burst model
for heavy compact objects with a solid surface. The consistency probability is
found to be below 10^{-7} for dynamical black-hole binaries, falling to below
10^{-13} for the additional exposures of black-hole candidates. These results
provide indirect evidence that black holes do have event horizons.

\\ ( http://arXiv.org/abs/astro-ph/0509758 , 156kb)