Highlights - Volume 501-2 (July II 2009)

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HIGHLIGHTS: this week in A&A

Volume 501-2 (July II 2009)


In section 5. Galactic structure, stellar clusters, and populations

“The massive star initial mass function of the Arches cluster”, by P. Espinoza, F. Selman, and J. Melnick, A&A 501, p. 563

Our understanding of galactic evolution at both high and low redshift is sensitive to the behavior of the IMF or Initial mass function of stars in different physical circumstances. One important question is whether the IMF differs in and around our galactic center from what is observed in the vicinity of the Sun. An important role in this discussion has been played by the Arches cluster located about 25 parsec in projection from the center where it has been claimed that the slope is flatter than the "Salpeter value" close to the Sun. The article by Espinoza et al., highlighted in this issue, finds instead that "a power law of Salpeter slope cannot be discarded" and thus the controversy continues. 


In section 5. Galactic structure, stellar clusters, and populations

“The RMS Survey: 6 cm continuum VLA observations towards candidate massive YSOs in the northern hemisphere”, by J.S. Urquhart et al., A&A 501, p. 539

Understanding high-mass star formation implies studying a well-chosen sample of high-mass protostars at all relevant wavelengths. The RMS survey (whose the latest excerpt is contained in the article by Urquhart et al. highlighted in this issue) is a good example of this and will be a fundamental basis for more detailed studies with ALMA, HERSCHEL, and other high-resolution instruments. 


In section 6. Interstellar and circumstellar matter

“An ISO/SWS study of the dust composition around S stars. A novel view of S-star dust”, by S. Hony, A.M. Heras, F.J. Molster, and K. Smolders, A&A 501, p. 609

Hony et al. use ISO SWS spectra of oxygen-rich and S-type AGB stars to study the nature of solid-state matter in the shells around these stars. They find systematic differences between the 10 micron silicate band in the two groups and find previously unreported dust-emission features in the S star spectra that are tentatively ascribed to Diopside. The O-rich stars exhibit dust features that are probably due to amorphous silicate and alumina. For these AGB star they find that the dust formation process appears to be controlled by the amount of free atomic oxygen that is available.

In section 9. The Sun

“Anisotropic viscous dissipation in three-dimensional magnetic merging solutions”, by I. J. D. Craig, Y.E. Litvinenko, A&A 501, p. 755

The impulsive conversion of magnetic energy into heating of plasma and acceleration of a flow is a common phenomenon. This paper points out the possibility that viscosity, often neglected in magnetic reconnection, can play a major role in heating reconnective flows.


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© Astronomy & Astrophysics 2009