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  • 1
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    A new investigation of photometric changes in RW Persei (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: New photoelectric observations of RW Per were obtained, and photometric solutions were carried out for these data, for earlier photoelectric observations, and for archival photographic observations. It is concluded that no third light exists in this binary, and that the original nodal variation explanation for historical changes in the depth of primary eclipse is therefore incorrect. A revised nodal variation hypothesis is suggested. It is also noted that these changes could have been produced by a gradual increase in the polar radius of the hot star, perhaps related to a change in that star's rotational velocity.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 103; 256-262
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  • 2
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    On the origin of the 1 keV diffuse X-ray background (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Soft X-ray sky survey data for high galactic latitudes are used to constrain simple geometric models for the source of the diffuse X-ray background at 1 keV. The intensity maps show two extended and enhanced features, in Eridanus and in the direction of the galactic center, with a relatively uniform sky away from these features and an observed degree of isotropy consistent with a model in which the 0.5-1.2 keV background consists of an isotropic extragalactic component and a thick disk galactic component. A temperature of 2-3 million K and an emission pressure of 0.004 per cm to the 6th pc are derived for the galactic component from an assumed spectrum of 11E to the -1.4 power photons/sq cm s sr keV. While consistent with the data, a local, isotropically distributed source model is shown to pose physical difficulties.
    Keywords: ASTROPHYSICS
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  • 3
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    The soft X-ray diffuse background and the structure of the local interstellar medium (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Data from five rocket flights of the Wisconsin soft X-ray sky survey, covering the southern galactic hemisphere with 6.5 deg spatial resolution between 0.1 and 2.0 keV, are presented as intensity maps. Analysis of the data in two energy bands below 0.3 keV is presented here. These low-energy X-rays appear to be emitted from a plasma of about one-million K, the bulk of which is closer to the sun than even the nearest 5 x 10 to the 19th/sq cm of neutral gas. No evidence is found for the presence of nearby small (radius of about 0.6 pc) clouds of cool neutral gas, as has been proposed by McKee and Ostriker (1977). The X-ray measurements are consistent with the small amounts of local neutral material inferred from Lyman-alpha absorption measurements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 4
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    Chromospherically active stars. 12: ADS 11060 C: A double lined K dwarf binary in a quintuple system (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: ADS 11060 C is a double lined spectroscopic binary with a period of 25.7631 days and an eccentricity of 0.565. Spectral types of the two stars are estimated as K7 V and MO V with a magnitude difference of about 0.55 mag in V. The stars appear to be somewhat metal rich with respect to the Sun. Despite the relatively large masses of 0.53 and 0.51 solar mass, our photometric observations find no evidence for eclipses and we estimate an inclination of 77 deg plus or minus 11 deg. ADS 11060 C is, however, photometrically variable with a period of 9 plus or minus 1 day and an amplitude of 0.05 mag in V. Thus, it is a newly identified BY Draconis variable. The center-of-mass velocity of ADS 11060 C and an estimated parallax of 0.030 sec support its physical association with ADS 11060 AB, making this a quintuple system. The projected separation of the AB-C system is nearly 1200 AU. Although the log lithium abundances of the two components of ADS 11060 C are only upper limits, less than or equal to -0.14, lithium abundances of the AB-C components appear to be consistent with those of similar stars in the alpha Persei and Pleiades clusters, suggesting an age of about 70 Myr for ADS 11060 AB-C. The system is a possible member of the Pleiades moving group. Listed as an optical counterpart to a source in the ROSAT Wide Field Camera extreme-ultraviolet bright source catalog, both ADS 11060 AB and C may contribute to the observed flux.
    Keywords: ASTROPHYSICS
    Type: The Astronomical Journal (ISSN 0004-6256); 108; 2; p. 694-700
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  • 5
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    The two variables in the triple system HR 6469 = V819 Her: One eclipsing, one spotted (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A complete BV light curve, from 14 nights of good data obtained with the Vanderbilt University-Tennessee State University (VU-TSU) automatic telescope, are presented and solved with the Wilson-Devinney program. Third light is evaluated, with the companion star brighter by 0.58(sup m) in V and 0.11(sup m) in B. The eclipses are partial. Inferred color indices yield F2 V and F8 V for the eclipsing pair and G8 IV-III for the distant companion star. After removing the variability due to eclipses, we study the residual variability of the G8 IV-III star over the ten years 1982 to 1992. Each yearly light curve is fit with a two-spot model. Three relatively long-lived spots are identified, with rotation periods of 85.9(sup d), 85.9(sup d), and 86.1(sup d). The weak and intermittent variability is understood because the G8 IV-III star has a Rossby number at the threshold for the onset of heavy spottedness.
    Keywords: ASTROPHYSICS
    Type: The Astronomical Journal (ISSN 0004-6256); 107; 4; p. 1521-1528
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  • 6
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    The complete sample of 1 Jansky BL Lacertae objects. I - Summary properties (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The first well-defined, homogeneous radio sample of 34 BL Lac objects selected from a large-area survey of sources brighter than 1 Jy at 5 GHz is presented. Extensive optical spectroscopy reveals weak emission lines in roughly 3/4 of the 34 BL Lac objects in the sample. Optical imaging reveals that the nearby BL Lac objects are not stellar, and that the surface brightness distribution of the surrounding fuzz is consistent with the host galaxies being bright ellipticals. The results suggest that gravitational lensing may affect three of the 17 high-redshift BL Lac objects in the sample. The observations do not support a microlensing scenario for the low-redshift objects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 374; 431-439
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