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Highlights - Volume 473-1 (October I 2007)

Details: Published on 03 September 2007

HIGHLIGHTS: this week in A&A

Volume 473-1 (October I 2007)

Star formation in the outer regions of M 33

“Particularly efficient star formation in M 33”, by E. Gardan, J. Braine, K.F. Schuster, N. Brouillet, and A. Sievers, A&A 473, p. 91

CO emission has been mapped at a large radius in the local group spiral galaxy M33 with HERA on the IRAM-30m. The results suggest that molecular gas is ubiquitous, even in the outer parts of spiral galaxies outside of the optical disk. Comparisons with star-formation indicators, such as the Spizer 8 and 24 microns maps, Hα, or Far UV emission, reveal high star-formation efficiency in these outside regions.

A new 3-D modeling method for reconstructing coronal structures

“Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona. I. Method”, by F. Saez, A. Llebaria, P. Lamy, and D. Vibert, A&A 473, p. 265

This paper describes an interesting 3-dimensional model for reproducing observations of coronal structures, such as streamers and CMEs.

In section 4. Extragalactic astronomy

“Multicolor observations of the afterglow of the short/hard GRB 050724”, by D. Malesani, S. Covino, P. D'Avanzo, V. D’Elia, et al., A&A 473, p. 77

This paper presents the photometry of the short GRB 050724, beginning about 1/2 day after detection, and the spectroscopy and imagining of its host galaxy (z = 0.26), a relatively low-luminosity, early type system with an old (2.6 Gyr) stellar population. The GRB occurred outside the galactic center (~ 3 kpc). There was no associated supernova, and the light curve is consistent with a binary merging event. The authors propose that the optical emission was related to an early, strong X-ray flare and that the steep optical decline is consistent with low collimation, implying a large energy release comparable to that of long GRBs. The flare properties require a strong Lorentz factor contrast between the colliding shells, and the authors argue that the central engine was active at late times.