Browsing by Subject "wide orbits"
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Item An Alma Constraint on the GSC 6214-210 B Circum-Substellar Accretion Disk Mass(2015-06) Bowler, Brendan P.; Andrews, Sean M.; Kraus, Adam L.; Ireland, Michael J.; Herczeg, Gregory; Ricci, Luca; Carpenter, John; Brown, Michael E.; Kraus, Adam L.We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of GSC 6214-210 A and B, a solar-mass member of the 5-10 Myr Upper Scorpius association with a 15 +/- 2 M-Jup companion orbiting at approximate to 330 AU (2 ''.2). Previous photometry and spectroscopy spanning 0.3-5 mu m revealed optical and thermal excess as well as strong H alpha and Pa beta emission originating from a circum-substellar accretion disk around GSC 6214-210 B, making it the lowest-mass companion with unambiguous evidence of a subdisk. Despite ALMA's unprecedented sensitivity and angular resolution, neither component was detected in our 880 mu m (341 GHz) continuum observations down to a 3 sigma limit of 0.22 mJy/beam. The corresponding constraints on the dust mass and total mass are <0.15M(circle plus) and <0.05 M-Jup, respectively, or <0.003% and <0.3% of the mass of GSC 6214-210 B itself assuming a 100:1 gas-to-dust ratio and characteristic dust temperature of 10-20 K. If the host star possesses a putative circum-stellar disk then at most it is a meager 0.0015% of the primary mass, implying that giant planet Formation has certainly ceased in this system. Considering these limits and its current accretion rate, GSC 6214210 B appears to be at the end stages of assembly and is not expected to gain any appreciable mass over the next few megayears.Item An Alma Disk Mass for the Candidate Protoplanetary Companion to FW Tau(2015-01) Kraus, Adam L.; Andrews, Sean M.; Bowler, Brendan P.; Herczeg, Gregory; Ireland, Michael J.; Liu, Michael C.; Metchev, Stanimir; Cruz, Kelle L.; Kraus, Adam L.We present ALMA observations of the FW Tau system, a close binary pair of M5 stars with a wide-orbit (300 AU projected separation) substellar companion. The companion is extremely faint and red in the optical and near-infrared, but boasts a weak far-infrared excess and optical/near-infrared emission lines indicative of a primordial accretion disk of gas and dust. The component-resolved 1.3mm continuum emission is found to be associated only with the companion, with a flux (1.78 +/- 0.03 mJy) that indicates a dust mass of 1-2M(circle plus). While this mass reservoir is insufficient to form a giant planet, it is more than sufficient to produce an analog of the Kepler-42 exoplanetary system or the Galilean satellites. The mass and geometry of the disk-bearing FW Tau companion remains unclear. Near-infrared spectroscopy shows deep water bands that indicate a spectral type later than M5, but substantial veiling prevents a more accurate determination of the effective temperature (and hence mass). Both a disk-bearing "planetary-mass" companion seen in direct light or a brown dwarf tertiary viewed in light scattered by an edge-on disk or envelope remain possibilities.Item Detection Of Low-Mass-Ratio Stellar Binary Systems(2013-01) Gullikson, Kevin; Dodson-Robinson, Sarah; Gullikson, Kevin; Dodson-Robinson, SarahO- and B-type stars are often found in binary systems, but the low binary mass-ratio regime is relatively unexplored due to observational difficulties. Binary systems with low mass ratios may have formed through fragmentation of the circumstellar disk rather than molecular cloud core fragmentation. We describe a new technique sensitive to G-and K-type companions to early B stars, a mass ratio of roughly 0.1, using high-resolution, high signal-to-noise spectra. We apply this technique to a sample of archived VLT/CRIRES observations of nearby B stars in the CO bandhead near 2300 nm. While there are no unambiguous binary detections in our sample, we identify HIP 92855 and HIP 26713 as binary candidates warranting follow-up observations. We use our non-detections to determine upper limits to the frequency of FGK stars orbiting early B-type primaries.