Search for spectral features in PRE bursts
Thermonuclear bursts that show photospheric radius-expansion (PRE) are
pretty rare in most sources, so much so that Chandra has only
observed a few of them in a decade of observations. In 2006 we made an
observation of a prolific PRE burster, 4U 1728-34, to try to catch some
bursts and search for spectral features near the peak. We got plenty of
bursts, but only 4 of them were likely PRE, and we saw no features. But, we
did find evidence for an extremely weak periodic variation in the X-ray
intensity, which if orbital in nature, means the neutron star orbits its
mass donor once every 10.77 minutes! Our paper was just accepted by ApJ, and
is available at arXiv:1009.2296.
Labels: 2010, /spectroscopy
Norbert's paper on the faint-state observations of Cir X-1 has just been accepted to ApJ. While the P-Cygni lines (present in earlier observations when the source was brighter) were absent, we found evidence for complex absorption effects, including warm (moderately ionized) absorbers with varying column density. This Chandra observation has proved popular lately, with 
Aimee's paper on the Fe Kα line profiles from the accretion columns of magnetic CVs was accepted by MNRAS last month. The paper extends Jason Cullen's nonlinear Monte-Carlo code to predict the degree of broadening expected from lines arising from close to the white dwarf. We used a Chandra observation of GK Per in outburst for comparison, and while the relative line strengths in the model is not set by the physical conditions, the results were promising.
