======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@aoc.nrao.edu http://www.aoc.nrao.edu/~gcnews ======================================================================== Vol. 25, No. 7 Oct 27, 2006 Recently submitted papers: -------------------------- 1) New Galactic Wolf-Rayet stars, and candidates. An annex to The VIIth Catalogue of Galactic Wolf-Rayet Stars (Hucht, A&A) 2) H.E.S.S. observations of the Galactic Center region and their possible dark matter interpretation (co-authors, PRL) 3) The detection of the (J,K)=(18,18) line of NH_3 (Wilson(1 et al., A&A) ------------------------------------------------------------------------ Email : K.A.van.der.Hucht@sron.nl Title : New Galactic Wolf-Rayet stars, and candidates. An annex to The VIIth Catalogue of Galactic Wolf-Rayet Stars Author(s): Karel A. van der Hucht Institute: (1) SRON National Institute for Space Research Sorbonnelaan 2 NL-3584 CA Utrecht the Netherlands Paper : A&A 458, 453 (2006) EPrint : astro-ph/0609008, Web : ftp://ftp.sron.nl/pub/karelh/UPLOADS/papers.dir/New-WR-Annex. pdf Abstract: This paper gathers, from the literature and private communication, 72 new Galactic Population I Wolf-Rayet stars and 17 candidate WCLd stars, recognized and/or discovered after the publication of The VIIth Catalogue of Galactic Wolf-Rayet Stars. This brings the total number of known Galactic Wolf-Rayet stars to 298, of which 24 (8%) are in open cluster Westerlund 1, and 60 (20%) are in open clusters near the Galactic Center. ------------------------------------------------------------------------ Email : loic.rolland@lapp.in2p3.fr Title : H.E.S.S. observations of the Galactic Center region and their possible dark matter interpretation Author(s): F. Aharonian and 106 alphabetically sorted co-authors Paper : PRL, 2006, accepted Abstract: The detection of gamma -rays from the source HESS J1745-290 in the Galactic Center (GC) region with the HESS array of Cherenkov telescopes in 2004 is presented. After subtraction of the diffuse gamma -ray emission from the GC ridge, the source is compatible with a point-source with spatial extent less than 1.2'(stat.) (95% CL). The measured energy spectrum above 160 GeV is compatible with a power-law with photon index of 2.25 +/- 0.04 (stat.) +/- 0.10 (syst.) and no significant flux variation is detected. These measurements are discussed in the framework of dark matter annihilation. It is found that the bulk of the VHE emission must have non-dark-matter origin. Loose constraints on the velocity-weighted annihilation cross section < sigma * v> are derived assuming the presence of an astrophysical non-dark-matter gamma -ray contribution. ------------------------------------------------------------------------ Email : p220hen@mpifr-bonn.mpg.de Title : The detection of the (J,K)=(18,18) line of NH_3 \gcbrk Author(s): T. L. Wilson(1,2), C. Henkel(1), S. Huettemeister(3) Institute: (1) Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany (2) European Southern Observatory, Karl-Schwarzschild-Stra\sse 2, 85748 Garching, Germany (3) Astronomisches Institut der Ruhr-Universitaet, D-44780 Bochum, Germany Paper : A&A, in press Abstract: A study of the metastable (J,K)=(18,18) line of ammonia (NH_3) is presented aiming at better defining the physical properties of molecular gas in extreme environments. The spectra were collected with the Effelsberg 100-m telescope and are analyzed in combination with other data using a rotation diagram (Boltzmann plot). The first astronomical detection of the metastable (J,K) = (18,18) line of NH_3 is reported. This is the NH_3 line with by far the highest energy, 3130 K above the ground state, detected in interstellar space. It is observed in absorption toward the galactic center star forming region Sgr B2. There is a clear detection toward Sgr B2 (M) and a likely one toward Sgr B2 (N). An upper limit for emission is determined for Orion KL. If we combine the (18,18) line results from Sgr B2 (M) with the previously measured (12,12) absorption line, we find a rotation temperature, T_rot, of >1300 K for the absorbing cloud. This is at least a factor of two higher than previously derived values from less highly excited ammonia lines. T_rot gives a lower limit to the kinetic temperature. There is a hot low density gas component in the envelope of Sgr B2. It is possible that the (18,18) line arises in this region. The radial velocity of the low density, hot envelope is the same as that of the dense hot cores, so the (18,18) line could also arise in the dense hot cores where non-metastable (J>K) absorption lines from energy levels of up to 1350 K above the ground state have been observed. A discussion of scenarios is presented. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Sera Markoff, Loránt Sjouwerman, Joseph Lazio, Cornelia Lang, Rainer Schödel, Robin Herrnstein - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please follow the instructions which are at http://www.aoc.nrao.edu/~gcnews/home/submission.shtml ========================================================================