GCNEWS
A Newsletter for Galactic Center Research
This Volume was edited by Angela Cotera & Heino Falcke
email: gcnews@aoc.nrao.edu
GCNEWS
Once again we have received a large number interesting results that have been submitted within the past months. First we have three papers (Yusef-Zadeh et al.; Backer & Sramek; Reid et al.) discussing the exact position and proper motion of Sgr A*. This is, of course, THE reference point for all astrometry in the Galactic Center and even the Galaxy. Probably most fascinating---from a technical point of view---is the fact that by observing Sgr A* with the VLBA (and the VLA) the rotation of our Sun around the Galactic Center can be measured. Considering it takes the Sun about 220 million years to complete an orbit, and that the VLBA can detect that motion in only two weeks, this is truly an amazing accomplishment.
On the subject of Sgr A*, another interesting bit of news has been provided in the papers by Bower et al. who have studied the polarization of this famous radio source. Although rumours abounded that it is (linearly) unpolarized, nobody realized that it is in fact a fairly strong circularly polarized source (see also Sault & Macquart). What is also curious is that this went unnoticed for this well-observed source for more than two decades. Perhaps this illustrates the point that there are still many new discoveries waiting to be made in the Galactic Center. As usual we currently lack any good explanations as to the causes of this unusual polarization.
Those of our readers more interested in stars in the GC and their evolution, will find a number of new papers and observations on the stellar content in the GC. Figer et al. present HST/NICMOS observations of the Arches and Quintuplet clusters which they find are indeed very young and suggest may be among the most massive in our Galaxy. In addition, NIR spectroscopy and even VLA observations (Lang et al.) directly probe the strong winds from these hot stars. Other papers discuss the stellar content on small scales near and far from the Black hole (Eckart et al., Philipp et al.). Can the stellar content be related to Sgr A*? Tal Alexander argues that it is, and explains how the stellar distribution and the presence of a black hole are naturally linked (see also Bailey & Davies).
In addition we also have an assortment of papers on the high-energy emission, non-thermal filaments, magnetic fields and a number of other facinating topics. As editors, we realize that we may have become so accustomed to the diverse and exciting results that pass through GCNEWS each month, that every now and again we need to sit back for a few moments, scan through the abstracts in GCNEWS, and enjoy diversity - again.