A bright thermonuclear X-ray burst simultaneously observed with Chandra and RXTE
Author(s)in't Zand, J. J. M.; Galloway, Duncan K.; Ballantyne, D. R.; Jonker, P. G.; Paerels, F. B. S.; Palmer, D. M.; Patruno, A.; Marshall, Herman Lee; Weinberg, Nevin N.; ... Show more Show less
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The prototypical accretion-powered millisecond pulsar SAX J1808.4−3658 was observed simultaneously with Chandra-LETGS and RXTE-PCA near the peak of a transient outburst in November 2011. A single thermonuclear (type-I) burst was detected, the brightest yet observed by Chandra from any source, and the second-brightest observed by RXTE. We found no evidence for discrete spectral features during the burst; absorption edges have been predicted to be present in such bursts, but may require a greater degree of photospheric expansion than the rather moderate expansion seen in this event (a factor of a few). These observations provide a unique data set to study an X-ray burst over a broad bandpass and at high spectral resolution (λ/Δλ = 200–400). We find a significant excess of photons at high and low energies compared to the standard black body spectrum. This excess is well described by a 20-fold increase of the persistent flux during the burst. We speculate that this results from burst photons being scattered in the accretion disk corona. These and other recent observations of X-ray bursts point out the need for detailed theoretical modeling of the radiative and hydrodynamical interaction between thermonuclear X-ray bursts and accretion disks.
DepartmentKavli Institute for Astrophysics and Space Research; Massachusetts Institute of Technology. Department of Physics
Astronomy & Astrophysics
in ’t Zand, J. J. M., D. K. Galloway, H. L. Marshall, D. R. Ballantyne, P. G. Jonker, F. B. S. Paerels, D. M. Palmer, A. Patruno, and N. N. Weinberg. “A bright thermonuclear X-ray burst simultaneously observed with Chandra and RXTE.” Astronomy & Astrophysics 553 (May 14, 2013): A83.
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