Highlights - Volume 493-1 (January I 2009)

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HIGHLIGHTS: this week in A&A

Volume 493-1 (January I 2009)


In section 6. Interstellar and circumstellar matter

“SiO outflow signatures toward massive young stellar objects with linearly distributed methanol masers”, by J.M. De Buizer, R. Redman, S.N. Longmore, J. Caswell, and P. Feldman, A&A 493, p. 127

There are good reasons to suppose that high-mass protostars are surrounded by disks, in particular because spherical accretion seems impossible in view of the expected high radiation pressure. It has been extremely difficult to find tracers of such disks partly because of the high obscuration due to the protostellar envelope. One plausible proposal, however, has been that methanol masers (which can be observed with VLBI) trace disks, thus allowing studies of disk kinematics. Unfortunately, recent observations and in particular the JCMT SiO(6-5) data presented by De Buizer et al. in this issue show that this hypothesis is often incorrect so we have to look elsewhere for reliable disk tracers. 


In section 6. Interstellar and circumstellar matter

“The N_2D^+/N_2H^+ ratio as an evolutionary tracer of Class 0 protostars”, by M. Emprechtinger, P. Caselli, N. H. Volgenau, J. Stutzki, and M. C. Wiedner, A&A 493, p. 89

The authors present new observations and a systematic study of the N2D+/N2H+ ratio in a sample of protostellar objects. They find a clear correlation of the N2D+/N2H+ ratio with a number of tracers of protostellar evolution: sources with high N_2D^+/N_2H^+ ratios show clear indications of infall where the infall signature disappears with decreasing deuterium fraction. 
In section 14. Catalogs and data

“The XMM-Newton serendipitous survey. V. The second XMM-Newton serendipitous source catalogue”, by M. G. Watson, A. C. Schröder, D. Fyfe et al., A&A 493, p. 339

The 2XMM catalog has been compiled from a new processing of the XMM-Newton EPIC camera pipeline data that is described in detail. Examples of data products, including catalog cross-correlations, spectra, and time series, are presented. The catalogue, the largest ever made at X-ray wavelengths, contains 246,897 detections covering over 500 deg2 with flux limits of 1, 9, and 25 x 10-14 erg/s/cm2 in the [0.5-2 keV], [2-12 keV], and [4.5-12 keV] bands, respectively, at > 90% sky coverage. Preliminary analysis of the catalog characteristics, including flux distributions and source counts, are presented. Simulations are discussed for false alarms and incompleteness.  


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