======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@aoc.nrao.edu http://www.aoc.nrao.edu/~gcnews ======================================================================== Vol. 29, No. 4 Feb 19, 2009 Recently submitted papers: -------------------------- 1) CO in OH/IR stars close to the Galactic centre (Winnberg et al., A&A) 2) A power-law break in the near-infrared power spectrum, of the Galactic center black hole (Meyer et al., ApJL) 3) A New Supernova Remnant Candidate and an Associated Outflow in the Sagittarius C Region (Tusuru et al., PASJ) ------------------------------------------------------------------------ Email : anders.winnberg@chalmers.se Title : CO in OH/IR stars close to the Galactic centre Author(s): A. Winnberg (1) and S. Deguchi (2) and M.J. Reid (3) and J. Nakashima (4,) (5) and H. Olofsson (1,) (6) and H.J. Habing (7) Institute: (1) Onsala Space Observatory, Observatorievaegen, SE-439 92 Onsala, Sweden, \email anders.winnberg@chalmers.se and Nobeyama Radio Observatory, Minamisaku, Nagano 384-1305, Japan and Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA and Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141,Taipei 106, Taiwan and Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong and Stockholm Observatory, AlbaNova University Centre, SE-106 91 Stockholm, Sweden and Sterrewacht Leiden, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands Paper : A&A, Feb 2009, in press EPrint : 0902.2347 Abstract: A pilot project has been carried out to measure circumstellar CO emission from three OH/IR stars close to the Galactic centre. The intention was to find out whether it would be possible to conduct a large-scale survey for mass-loss rates using, for example, the Atacama Large Millimeter Array (ALMA). Such a survey would increase our understanding of the evolution of the Galactic bulge. Two millimetre-wave instruments were used: the Nobeyama Millimeter Array at 115 GHz and the Submillimeter Array at 230 GHz. An interferometer is necessary as a `spatial filter' in this region of space because of the confusion with interstellar CO emission. Towards two of the stars, CO emission was detected with positions and radial velocities coinciding within the statistical errors with the corresponding data of the associated OH sources. However, for one of the stars the line profile is not what one expects for an unresolved expanding circumstellar envelope. We believe that this CO envelope is partially resolved and that this star therefore is a foreground star not belonging to the bulge. The results of the observations have shown that it is possible to detect line profiles of circumstellar CO from late-type stars both within and in the direction of the Galactic bulge. ALMA will be able to detect CO emission in short integrations with sensitivity sufficient to estimate mass-loss rates from a large number of such stars. ------------------------------------------------------------------------ Email : leo-meyer@gmx.de Title : A power-law break in the near-infrared power spectrum, of the Galactic center black hole Author(s): L. Meyer (1), T. Do (1), A. Ghez (1), M. R. Morris (1), S. Yelda (1) R. Schoedel (2) A. Eckart (3) Institute: (1) Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (2) Instituto de Astrofisica de Andalucia - CSIC, Camino Bajo de Huetor 50, 18008 Granada, Spain (3) Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln, Germany Paper : ApJ Letters, accepted Abstract: Proposed scaling relations of a characteristic timescale in the X-ray power spectral density of galactic and supermassive black holes have been used to argue that the accretion process is the same for small and large black holes. Here, we report on the discovery of this timescale in the near-infrared radiation of Sgr A*, the 4* 10^6 M_\sun black hole at the center of our Galaxy, which is the most extreme sub-Eddington source accessible to observations. Previous simultaneous monitoring campaigns established a correspondence between the X-ray and near-infrared regime and thus the variability timescales are likely identical for the two wavelengths. We combined Keck and VLT data sets to achieve the necessary dense temporal coverage, and a time baseline of four years allows for a broad temporal frequency range. Comparison with Monte Carlo simulations is used to account for the irregular sampling. We find a timescale at 154^+124_-87 min (errors mark the 90% c onfidence limits) which is inconsistent with a recently proposed scaling relation that uses bolometric luminosity and black hole mass as parameters. However, our result fits the expected value if only linear scaling with black hole mass is assumed. We suggest that the luminosity-mass-timescale relation applies only to black hole systems in the soft state. In the hard state, which is characterized by lower luminosities and accretion rates, there is just linear mass scaling, linking Sgr A* to hard state stellar mass black holes. ------------------------------------------------------------------------ Email : tsuru@cr.scphys.kyoto-u.ac.jp Title : A New Supernova Remnant Candidate and an Associated Outflow in the Sagittarius C Region Author(s): Takeshi Go Tsuru (1), Masayoshi Nobukawa (1), Hiroshi Nakajima (2), Hironori Matsumoto (1), Katsuji Koyama (1), Shigeo Yamauchi (3) Institute: (1) Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502 (2) Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (3) Faculty of Humanities and Social Sciences, Iwate University, 3-18-34 Ueda, Morioka, Iwate 020-8550 Paper : PASJ, Jan 2009 EPrint : 0902.1308 Abstract: We present the Suzaku results on a new candidate of a supernova remnant (SNR) in the Sagittarius C region. We detected diffuse X-rays of an elliptical shape (G 359.41-0.12) and chimney-like structure (the Chimney), both of which are fitted with a thin thermal model of KT 1 keV temperature. The absorption columns are same between these two structures, indicating the both are located at the same distance in the same line of sight. The narrow band image and one-dimensional profile of S-XV K alpha at 2.45 keV show that the Chimney is emanating from G 359.41-0.12. Therefore these two sources are physically connected with each other. The sum of thermal energies of the Chimney and G 359.41-0.12 is estimated to be 1.4* 10^50 ergs, typical for a Galactic SNR. G 359.41-0.12 is likely a new SNR candidate and the Chimney is an associated outflow. ------------------------------------------------------------------------ (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, Masaaki Sakano, Feng Yuan - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please follow the instructions which are at http://www.aoc.nrao.edu/~gcnews/home/submission.shtml ========================================================================