======================================================================== 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. 4 Sep 7, 2006 Recently submitted papers: -------------------------- 1) Pinwheels in the Quintuplet Cluster (Tuthill et al., Aug) 2) Production of Hypervelocity Stars through Encounters with Stellar-Mass Black Holes in the Galactic Centre (O'Leary & Loeb, MNRAS) ------------------------------------------------------------------------ Email : angelle.tanner@jpl.nasa.gov Title : Pinwheels in the Quintuplet Cluster Author(s): Peter Tuthill, John Monnier, Angelle Tanner, Donald Figer, Andrea Ghez, William Danchi Paper : Aug 2006, in press EPrint : astro-ph/0608427 Abstract: The five enigmatic "Cocoon stars" after which the Quintuplet cluster was christened have puzzled astronomers since their discovery. Their extraordinary cool, featureless thermal spectra have been attributed to various stellar types from young to highly evolved, while their absolute luminosities places them among the supergiants. We present diffraction-limited images from the Keck 1 telescope which resolves this debate with the discovery of rotating spiral plumes characteristic of colliding-wind binary "pinwheel" nebulae. Such elegant spiral structures, found around high-luminosity Wolf-Rayet stars, have recently been implicated in the behavior of supernovae lightcurves in the radio and optical. ------------------------------------------------------------------------ Email : roleary@cfa.harvard.edu Title : Production of Hypervelocity Stars through Encounters with Stellar-Mass Black Holes in the Galactic Centre Author(s): Ryan M. O'Leary, Abraham Loeb Institute: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 10, Cambridge, MA 02138, USA Paper : MNRAS, Sept. 2006, submitted EPrint : astro-ph/0609046 Abstract: Stars within 0.1 pc of the supermassive black hole Sgr A* at the Galactic centre are expected to encounter a cluster of stellar-mass black holes (BHs) that have segregated to that region. Some of these stars will scatter off an orbiting BH and be kicked out of the Galactic centre with velocities up to 2000 km/sec . We calculate the resulting ejection rate of hypervelocity stars (HVSs) by this process under a variety of assumptions, and find it to be comparable to the tidal disruption rate of binary stars by Sgr A*, first discussed by Hills (1988). Under some conditions, this novel process is sufficient to account for all the B-type HVSs observed in the halo, and to dominate the production rate of all HVSs with lifetimes much less than the relaxation time-scale at a distance 2 pc from Sgr A* (> 2 Gyr). Since HVSs are produced by at least two unavoidable processes, the statistics of HVSs could reveal bimodal velocity and mass distributions, and can constrain the distribution of BHs and stars in the innermost 0.1 pc around Sgr A*. ------------------------------------------------------------------------ (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 ========================================================================