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  • 1
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    A cooling flow cluster at redshift z = 0.2 (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The cluster of galaxies 1E0839.9 + 2938, discovered in X-ray observations by Nesci et al. (1988), is characterized on the basis of VLA 6-cm radio observations, Whipple Observatory CCD photometry, and spectroscopic observations obtained with the Multiple Mirror Telescope and the 88-inch University of Hawaii Telescope at Mauna Kea. The data are presented in tables, maps, and sample images and spectra and briefly characterized. The bright X-ray object is identified with a cluster at redshift z = 0.195; its central galaxy has radio emission of 1.1 x 10 exp 24 W/Hz as well as strong optical line emission which is not restricted to its nucleus. It is concluded that 1E0839.9 + 2938 is a cooling-flow cluster similar to 3C295 (found at z = 0.461 by Henry et al., 1986). The need for space observations (by Rosat or the AXAF) to determine the object's X-ray luminosity distribution is indicated.
    Keywords: ASTROPHYSICS
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  • 2
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    The extended medium sensitivity survey distant cluster sample - X-ray data and interpretation of the luminosity evolution (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The X-ray properties of a cluster of galaxies subsample of the Einstein Extended Medium Sensitivity Survey is described. A summary of this sample and its implication has been presented previously; this paper gives the full details. The cluster subsample is 98.4 percent identified and contains 93 X-ray-selected clusters to a redshift of 0.58. The cluster X-ray luminosity function at three cosmic epochs is derived. While the present luminosity function agrees with previous determinations at the lowest redshifts, it is found that the volume density of high-luminosity clusters is greater now than it was in the past. The normalization, shape, and time dependence of the luminosity function can be described by a simple hierarchical formation model with parameters which also describe the temperature function of an independent sample of low-redshift clusters. In this model the comoving hot gas density remains constant with time at least to redshifts of order 0.35.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 386; 408-419
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  • 3
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    X-ray selected high redshift clusters of galaxies (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Studies of the evolution of X-ray emission from clusters of galaxies have so far used distant clusters discovered optically and then observed at X-ray wavelengths (Henry et al., 1982; Henry and Lavery, 1984). A different approach to the study of cluster evolution is to use clusters selected directly by their X-ray emission, since X-ray selection is extremely successful at discovering high-redshift clusters (up to z = 0.5). The Extension of the Medium Sensitivity Survey, a study of serendipitous X-ray sources discovered with the Einstein Imaging Proportional Counter, has so far provided a sample of more than 60 clusters with relatively high redshifts. Upon completion of the identification programs the sample will include over 100 clusters. Here the data currently available are presented, and the basic properties of this new sample of clusters of galaxies are discussed. A preliminary number-counts distribution is also derived.
    Keywords: ASTROPHYSICS
    Type: High redshift and primeval galaxies; Jun 29, 1987 - Jul 03, 1987; Paris; France
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  • 4
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    Hubble Space Telescope spectra of the phase-modulated wind in the SMC O+WR binary R31 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present HST/GHRS profiles of C IV 1500 A at conjunction phases 0.21, 0.26, and 0.72 of the 6.5 day O6+WN3 binary R31 in the SMC. We also use IUE archival data covering other orbital phases, There are strong changes in the line profile, depending on the line of view through an ionization bubble near the WR star. We fit a model for the stellar wind and discuss the unique probe of mass loss found in this system. We also discuss the strong interstellar components of the line arising in the Galactic foreground and in the SMC.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 410; 2; p. 803-807.
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  • 5
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    The Extended Medium Sensitivity Survey distant cluster sample - X-ray cosmological evolution (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The X-ray luminosity function of clusters of galaxies is determined at different cosmic epochs using data from the Einstein Observatory Extended Medium Sensitivity Survey. The sample consists of 67 X-ray-selected clusters that have been grouped in three redshift shells. Evolution is detected in the X-ray properties of clusters. The present volume density of high-luminosity clusters is found to be greater than it was in the past. Given the still limited data set, this result should be regarded as preliminary. It can be interpreted as the consequence of either luminosity evolution or modest density evolution.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 356; L35-L38
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  • 6
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    Hubble Space Telescope spectroscopy of OB stars in M31 (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: We have obtained UV spectra of two luminous hot stars in M31 with the Hubble Space Telescope. The stars are of late O and WN spectral type and lie on opposite sides of M31. We derive UV extinction curves for M31 which differ from both the Galaxy and the LMC. We find differences between the IS absorbers in both lines of sight in M31 and in the Galactic halo. The stellar wind-driven mass loss of the stars is found to be 10 times lower than in similar Galactic stars. One star appears to be an eclipsing W-R binary.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 400; 1; p. L35-L38.
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  • 7
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    The number count distribution for X-ray-selected BL Lacertae objects and constraints on the luminosity function (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 369; 314-319
    Format: text
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