Browsing by Subject "astrometric orbits"

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    New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. IX. HD 54371, HR 2692, And 16 Ursa Majoris
    (2015-02) Fekel, Francis C.; Williamson, Michael H.; Muterspaugh, Matthew W.; Pourbaix, Dimitri; Willmarth, Daryl; Tomkin, Jocelyn; Tomkin, Jocelyn
    With extensive sets of new radial velocities we have determined orbital elements for three previously known spectroscopic binaries, HD 54371, HR 2692, and 16 UMa. All three systems have had the lines of their secondaries detected for the first time. The orbital periods range from 16.24 to 113.23 days, and the three binaries have modestly or moderately eccentric orbits. The secondary to primary mass ratios range from 0.50 to 0.64. The orbital dimensions (a(1) sin i and a(2) sin i) and minimum masses (m(1) sin(3) i and m(2) sin(3) i) of the binary components all have accuracies of <= 1%. With our spectroscopic results and the Hipparcos data, we also have determined astrometric orbits for two of the three systems, HR 2692 and 16 UMa. The primaries of HD 54371 and 16 UMa are solar-type stars, and their secondaries are likely K or M dwarfs. The primary of HR 2692 is a late-type subgiant and its secondary is a G or K dwarf. The primaries of both HR 2692 and 16 UMa may be pseudosynchronously rotating, while that of HD 54371 is rotating faster than its pseudosynchronous velocity.
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    A Probable Close Brown Dwarf Companion To GJ 1046 (M 2.5V)
    (2008-06) Kurster, M.; Endl, M.; Reffert, S.; Endl, M.
    Context. Brown dwarf companions to stars at separations of a few AU or less are rare objects, and none have been found so far around early-type M dwarfs (M 0V-M5V). With GJ 1046 (M 2.5V), a strong candidate for such a system with a separation of 0.42 AU is presented. Aims. We aim at constraining the mass of the companion in order to decide whether it is a brown dwarf or a low-mass star. Methods. We employed precision RV measurements to determine the orbital parameters and the minimum companion mass. We then derived an upper limit to the companion mass from the lack of disturbances of the RV measurements by a secondary spectrum. An even tighter upper limit is subsequently established by combining the RV-derived orbital parameters with the recent new version of the Hipparcos Intermediate Astrometric Data. Results. For the mass of the companion, we derive m >= 26.9 M-Jup from the RV data. Based on the RV data alone, the probability that the companion exceeds the stellar mass threshold is just 6.2%. The absence of effects from the secondary spectrum lets us constrain the companion mass to m <= 229 M-Jup. The combination of RV and Hipparcos data yields a 3 sigma upper mass limit to the companion mass of 112 M-Jup with a formal optimum value at m = 47.2 M-Jup. From the combination of RV and astrometric data, the chance probability that the companion is a star is 2.9%. Conclusions. We have found a low-mass, close companion to an early-type M dwarf. While the most likely interpretation of this object is that it is a brown dwarf, a low-mass stellar companion is not fully excluded.