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H- and K-Band Spectra of Brown Dwarf Candidates in the Core of the ? Ophiuchi Molecular Cloud Complex
We present low-resolution H- and K-band spectra of 14 brown dwarfcandidates located in the core of the ? Ophiuchi molecular cloudcomplex. Half of the spectra exhibit broad water absorption bandscharacteristic of M stars, while half of the spectra are featureless. Wederive spectral types and effective temperatures for the sevencandidates whose spectra exhibit water absorption bands by comparing thestrength of these bands with those of standard M dwarf stars. Weestimate their masses by first combining the spectral types withpublished near-infrared photometry to estimate bolometric luminositiesand then by comparing their positions in a Hertzsprung-Russell diagramwith theoretical evolutionary tracks and isochrones. The masses of fourof the candidates lie below the substellar limit when the errors intheir effective temperatures and bolometric luminosities are considered,while the remaining three candidates have masses on thestellar-substellar border. We find our mass estimates to be consistentwith those determined using near-infrared photometry alone. The derivedages of three candidates are considerably older than the previouslydetermined age of the embedded cluster. If these objects are members ofthe cluster, then they may belong to an older and previouslyunrecognized population of the ? Ophiuchi molecular cloud complex.
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| 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
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Akrep |
| Sað Açýklýk: | 15h50m02.10s |
| Yükselim: | -25°24'35.5" |
| Görünürdeki Parlaklýk: | 8.741 |
| Uzaklýk: | 262.467 parsek |
| özdevim Sað Açýklýk: | -11.8 |
| özdevim Yükselim: | -20.5 |
| B-T magnitude: | 8.963 |
| V-T magnitude: | 8.76 |
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