Highlights - Volume 465-2 (April II 2007)

“X-ray monitoring of optical novae in M31 from July 2004 to February 2005”, by W. Pietsch et al. A&A 465, p. 375

“Supersoft” X-ray sources are a possible progenitor system for SN Ia and other important post-outburst cataclysmic systems (also related to recurrent novae). Using ROSAT and early XMM-Newton and Chandra observations of M 31, this study provides a complete catalog of novae and related systems from archival data obtained between July 2004 to February 2005. Among systems within one year of outburst, an important interval for turnoff, eleven out of 34 novae were detected. An additional seven novae remained detectable in X-rays up to 10 years after outburst. The authors conclude that the number of X-ray-detected optical novae is higher than previously expected, an important indication of the physical properties of these systems.

Structure of the turbulent interstellar atomic hydrogen

The aim of this pair of articles is to understand the dynamics of the atomic gas by using 2D, large-scale and numerical simulation with a wide dynamic range and a detailed comparison to large-scale H I observations. The range of spatial scale is particularly large, that is, three orders of magnitude including thermal effects. The authors conclude that the “turbulence” within the cold interstellar atomic gas is mainly the result of individual, long-lived cloudlet kinematics rather than dissipative dynamics within a nearly homogeneous medium.

Binary star progenitors of long gamma-ray bursts

It has become clear over the past few years that understanding the mechanism of gamma-ray bursts requires comprehension of their stellar progenitors. This paper examines a possible scenario for producing a "collapsar" involving the evolution of a massive binary, which gives rise to a rapidly rotating Wolf-Rayet star.