Hubble Space TelescopeObservations of M Subdwarfs
نویسندگان
چکیده
منابع مشابه
M Subdwarfs: the Population Ii Luminosity Function
We present results of a study of very low mass halo stars. Using a sample of proper motion stars identified from plate material taken as part of the first and second Palomar Sky Surveys, we measure the space density, metallicity distribution, and kinematics of the Population II M subdwarfs. Our overall luminosity function is in good agreement with previous analyses of the space density of nearb...
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The Cosmic Evolution Survey (COSMOS) was initiated with an extensive allocation (590 orbits in Cycles 12-13) using the Hubble Space Telescope (HST) for high resolution imaging. Here we review the characteristics of the HST imaging with the Advanced Camera for Surveys (ACS) and parallel observations with NICMOS and WFPC2. A square field (1.8⊓⊔) has been imaged with single-orbit ACS I-F814W expos...
متن کاملForever Young: High Chromospheric Activity in M Subdwarfs
We present spectroscopic observations of two halo M subdwarfs which have Hα emission lines. We show that in both cases close companions are the likely cause of the chromospheric activity in these old, metal-poor stars. We argue that Gl 781 A’s unseen companion is most likely a cool helium white dwarf. Gl 455 is a near-equal-mass M subdwarf (sdM) system. Gl 781 A is rapidly rotating with v sin i...
متن کاملFaint Blue Objects in the Hubble Deep Field–South Revealed: White Dwarfs, Subdwarfs, and Quasars
We explore the nature of the faint blue objects in the Hubble Deep Field South. We have derived proper motions for the point sources in the Hubble Deep Field South using a 3-year baseline. Combining our proper motion measurements with spectral energy distribution fitting enabled us to identify 4 quasars and 42 stars, including 3 white dwarf candidates. Two of these white dwarf candidates, HDFS ...
متن کاملM-Subdwarfs: Spectroscopic Classification and the Metallicity Scale
We present a spectroscopic classification system for M-dwarfs and M-subdwarfs based on quantitative measures of TiO and CaH features in the region λλ6200−7400Å. Our sample of cool stars covers the range from solar metallicity stars to the most extreme subdwarfs known. Using synthetic spectra computed by Allard and Hauschildt (1995), we derive metallicities for the stars. Stars are classified as...
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ژورنال
عنوان ژورنال: Publications of the Astronomical Society of the Pacific
سال: 2000
ISSN: 0004-6280,1538-3873
DOI: 10.1086/316558