======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@mpifr-bonn.mpg.de http://www.mpifr-bonn.mpg.de/gcnews ======================================================================== Vol. 11, No. 9 Apr 11, 2000 Recently submitted papers: -------------------------- 1) Stellar Dynamics in the Galactic centre: Proper Motions and Anisotropy (Genzel et al., MNRAS) 2) A Second Luminous Blue Variable in the Quintuplet Cluster (Geballe et al., ApJL) ANNOUNCEMENT: ------------- 3) Release of the INES (IUE) Archive (Talavera, LAEFF/ESA) ------------------------------------------------------------------------ Email : lowell@mpe.mpg.de Title : Stellar Dynamics in the Galactic centre: Proper Motions and Anisotropy Author(s): R. Genzel^1, C.Pichon^2,3, A.Eckart^1, O.E.Gerhard^2 and T.Ott^1 Institute: ^1 Max-Planck Institut fuer extraterrestrische Physik, Garching, Germany, ^2 Astronomisches Institut, Universitaet Basel, Switzerland, ^3 Observatoire de Strasbourg, 11 rue de l'Observatoire, Strasbourg, France Paper : MNRAS, submitted EPrint : astro-ph/0001428 Abstract: We report a new analysis of the stellar dynamics in the Galactic centre, based on improved sky and line-of-sight velocities for more than one hundred stars in the central few arcseconds from the black hole candidate SgrA*. The main results are: (1) Overall the stellar motions do not deviate strongly from isotropy. For those 32 stars with a determination of all three velocity components the absolute, line of sight and sky velocities are in good agreement, consistent with a spherical star cluster. Likewise the sky-projected radial and tangential velocities of all 104 proper motion stars in our sample are also consistent with overall isotropy. (2) However, the sky-projected velocity components of the young, early type stars in our sample indicate significant deviations from isotropy, with a strong radial dependence. Most of the bright HeI emission line stars at separations from 1" to 10'' from SgrA* are on tangential orbits. This tangential anisotropy of the HeI stars and most of the brighter members of the IRS16 complex is largely caused by a clockwise (on the sky) and counter-rotating (line of sight, compared to the Galaxy), coherent rotation pattern. The overall rotation of the young star cluster probably is a remnant of the original angular momentum pattern in the interstellar cloud from which these stars were formed. (3) The fainter, fast moving stars within 1^'' from SgrA* appear to be largely moving on radial or very elliptical orbits. We have so far not detected deviations from linear motion (i.e. acceleration) for any of them. Most of the SgrA* cluster members also are on clockwise orbits. Spectroscopy indicates that they are early type stars. We propose that the SgrA* cluster stars are those members of the early type cluster that happen to have small angular momentum and thus can plunge to the immediate vicinity of SgrA*. (4) We derive an anisotropy-independent estimate of the Sun-Galactic centre distance between 7.8 and 8.2 kpc, with a formal statistical uncertainty of +/- 0.9 kpc. (5) We explicitly include velocity anisotropy in estimating the central mass distribution. We show how Leonard-Merritt and Bahcall-Tremaine mass estimates give systematic offsets in the inferred mass of the central object when applied to finite concentric rings for power law clusters. Corrected Leonard-Merritt projected mass estimators and Jeans equation modelling confirm previous conclusions (from isotropic models) that a compact central mass concentration (central density >=10^ 12.6 M_sun pc^ -3) is present and dominates the potential between 0.01 and 1 pc. Depending on the modelling method used the derived central mass ranges between 2.6 and 3.3 * 10^6 M_sun for R_sun=8.0 kpc. ------------------------------------------------------------------------ Email : tgeballe@noao.edu Title : A Second Luminous Blue Variable in the Quintuplet Cluster Author(s): T. R. Geballe(1), F. Najarro(2), D. F. Figer(3) Institute: (1) Gemini Observatory, 670 N. A'ohoku Pl., Hilo, HI 96720 (2) Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain (3) Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Paper : ApJL 530, L57 Abstract: H and K band moderate resolution and 4 microns high resolution spectra have been obtained for FMM362, a bright star in the Quintuplet Cluster near the Galactic Center. The spectral features in these bands closely match those of the Pistol Star, a luminous blue variable and one of the most luminous stars known. The new spectra and previously-obtained photometry imply a very high luminosity for FMM362, L >= 10^6 \Lo, and a temperature of 10,000 - 13,000 K. Based on its luminosity, temperature, photometric variability, and similarities to the Pistol Star, we conclude that FMM362 is a luminous blue variable. ------------------------------------------------------------------------ ANNOUNCEMENT: Release of the INES Archive Antonio Talavera INES Project Scientist The International Ultraviolet Explorer (IUE) Archives have been delivered to the world scientific community on 21st March. ESA, in collaboration with the Spanish Laboratory of Space Astrophysics and Theoretical Physics (LAEFF) belonging to INTA (National Institute of Air and Space Technology), has developed and set up the INES system to access IUE Data. INES (IUE Newly Extracted Spectra) is a complete astronomical archive and data-distribution system. Its release to the community represents the final activity by ESA in the context of the IUE project. From now LAEFF, on behalf of the international astronomical community, will be responsible of maintaining INES, making it available and providing world-wide support to scientists using IUE data. The IUE Archive contains more than 110,000 spectra of more that 11,000 astronomical objects. All data are fully reduced and calibrated. The INES archive consists of: - an access catalog containing the parameters required to query the archive and evaluate the observations, - a publications catalog which links each spectrum to the publications in which it has been used via the ADS, - and the data themselves (low dispersion spectra, high dispersion spectra rebinned to the low resolution wavelength step, full high dispersion concatenated spectra, and bi-dimensional low dispersion images). The INES Archive can be accessed at http://ines.vilspa.esa.es. Users can consult the catalogue, preview the spectra and download the data with a standard browser from the Principal Centre at LAEFF, its Mirror Centre located at the Canadian Astronomical Data Centre or any of the National Centres spread in all continents. This distributed system guarantees the availability and efficient access to the data. Questions about the INES archive can be directed to the INES Help Desk at ineshelp@iuearc.vilspa.esa.es or at http://iuearc.vilspa.esa.es/ines_jb/HelpDesk/. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================