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Infrared Spectroscopy of the Ultra-Low-Mass Binary Oph 162225-240515
Binary properties are an important diagnostic of the star and browndwarf formation processes. While wide binaries appear to be rare in thesubstellar regime, recent observations have revealed Ophiuchus162225-240515 (2MASS J16222521-2405139) as a likely young ultra-low-massbinary with an apparent separation of ~240 AU. Here we presentlow-resolution near-infrared spectra of the pair from NTT/SOFI (R~600)and VLT/ISAAC (R~1400), covering the 1.0-2.5 ?m spectral region. Bycomparing them to model atmospheres from Chabrier & Baraffe andBurrows et al., we confirm the surface temperatures to beTA=2350+/-150 K and TB=2100+/-100 K for the twocomponents of the binary, consistent with earlier estimates from opticalspectra. Using gravity-sensitive K I features, we find the surfacegravity to be significantly lower than field dwarfs of the same spectraltype, providing the best evidence so far that these objects are indeedyoung. However, we find that models are not sufficiently reliable toinfer accurate ages/masses from surface gravity. Instead, we derivemasses of MA=13+8-4MJ andMB=10+5-4MJ for the twoobjects using the well-constrained temperatures and assuming an age of1-10 Myr, consistent with the full range of ages reported for the Ophregion.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Far-Ultraviolet Stellar Photometry: Fields Centered on rho Ophiuchi and the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..104..101S&db_key=AST
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Radial velocities for early type stars in six galactic regions
Coudespectroscopy has been carried out for 353 stars of spectral typesB0-A0 and V magnitudes between 6.5 and 10.8 m, selected in six regions(three northern and three southern) close to the galactic plane at thegalactic longitudes 135, 175, 315 and 350 deg. The radial velocitieswere obtained by cross-correlating each spectrogram with a referencespectrogram giving an internal error of 1.4 km/s.
| Four-colour and H-beta photometry for early type stars in three southern galactic regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41...85L&db_key=AST
| Investigations of a Milky Way field in Scorpius. VI. Radial velocities of bright O and B stars
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