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Mon Sep 27, 2010

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

Tue Sep 25, 2007

The Variable Warm Absorber in Circinus X-1

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 another paper analysing the same data posted just weeks earlier.

Read the paper arXiv:0709.3336

Labels: 2007, /spectroscopy

Mon May 07, 2007

Fe Kα Lines in MCVs

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.

Read the paper (astro-ph/0704.1516)

Labels: 2007, /spectroscopy