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  • Astrophysics  (2)
  • Astronomy  (1)
  • 1
    Publication Date: 2018-06-11
    Description: The Two Micron All Sky Survey (2MASS) photometric calibration observations cover approximately 6 square degrees on the sky in 35 'calibration fields,' each sampled in nominal photometric conditions between 562 and 3692 times during the 4 years of the 2MASS mission. We compile a catalog of variables from the calibration observations to search for M dwarfs transited by extrasolar planets. We present our methods for measuring periodic and nonperiodic flux variability. From 7554 sources with apparent K(sub s) magnitudes between 5.6 and 16.1, we identify 247 variables, including extragalactic variables and 23 periodic variables. We have discovered three M dwarf eclipsing systems, including two candidates for transiting extrasolar planets.
    Keywords: Astronomy
    Type: The Astrophysical Journal Supplement Series; Volume 175; 191-228
    Format: text
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  • 2
    Publication Date: 2019-08-17
    Description: We have obtained 1 1.7 and 17.9 micron images at the Keck I telescope of the circumstellar dust emission from L(sub 2) Pup, which is one of the nearest ( D = 61 pc) mass-losing, pulsating red giants that has a substantial infra-red excess. We propose that the star is losing mass at a rate of approx.3 x 10(exp -7) Solar Mass/yr. Given its relatively low luminosity (approx. 1500 Solar Luminosity), relatively high effective temperature (near 3400 K), relatively short period (approx. 140 days), and inferred gas outflow speed of 3.5 km/s, standard models for dust-driven mass loss do not apply. Instead, the wind may be driven by the stellar pulsations, with radiation pressure on dust being relatively unimportant. as described in some recent calculations. L(sub 2) Pup may serve as the prototype of this phase of stellar evolution, in which a star could lose approx. 15% of its initial main-sequence mass. Subject headings: circumstellar matter - stars: individual (L2 Puppis) - stars: mass loss
    Keywords: Astrophysics
    Type: The Astrophysical Journal (ISSN 0004-637X); 569; 2, Pt. 1; 964-974
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  • 3
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    In:  Other Sources
    Publication Date: 2019-08-17
    Description: Using the Keck I telescope, we have obtained 11.7 and 18.7 microns images of the circumstellar dust emission from AB Aur, a Herbig Ae star. We find that AB Aur is probably resolved at 18.7 microns with an angular diameter of 1.2 in. at a surface brightness of 3.5 Jy arc/sq sec. Most of the dust mass detected at millimeter wavelengths does not contribute to the 18.7 microns emission, which is plausibly explained if the system possesses a relatively cold massive disk. We find that models with an optically thick, geometrically thin disk surrounded by an optically thin spherical envelope fit the data somewhat better than flared disk models.
    Keywords: Astrophysics
    Type: ISSN 0004-637X , The Astrophyical Journal; 591; 1 Part 1; 267-274
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