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GEMINI near-infrared spectroscopic observations of young massive stars embedded in molecular clouds
K-band spectra of young stellar candidates in four Southern hemisphereclusters have been obtained with the Gemini Near-Infrared Spectrographin Gemini South. The clusters are associated with IRAS sources that havecolours characteristic of ultracompact HII regions. Spectral types wereobtained by comparison of the observed spectra with those of anear-infrared (NIR) library; the results include the spectralclassification of nine massive stars and seven objects confirmed asbackground late-type stars. Two of the studied sources have K-bandspectra compatible with those characteristic of very hot stars, asinferred from the presence of CIV, NIII and NV emission lines at 2.078,2.116 and 2.100 ?m, respectively. One of them, I16177_IRS1, has aK-band spectrum similar to that of Cyg OB2 7, an O3If* supergiant star.The nebular K-band spectrum of the associated Ultra-Compact (UC) HIIregion shows the s-process [KrIII] and [SeIV] high excitation emissionlines, previously identified only in planetary nebula. One young stellarobject was found in each cluster, associated with either the main IRASsource or a nearby resolved Midecourse Space eXperiment (MSX) component,confirming the results obtained from previous NIR photometric surveys.The distances to the stars were derived from their spectral types andpreviously determined JHK magnitudes; they agree well with the valuesobtained from the kinematic method, except in the case of IRAS15408-5356, for which the spectroscopic distance is about a factor of 2smaller than the kinematic value.
| 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
| Far-ultraviolet stellar photometry: Fields in Sagittarius and Scorpius
Far-ultraviolet photometry for 741 objects in a field in Sagittariuscentered near M8 and 541 objects in a field centered near sigma Scorpiiis presented. These data were extracted from electographic imagesobtained with two cameras during a shuttle flight in 1991 April/May. Thecameras provided band passes with lambdaeff = 1375 A andlambdaeff = 1781 A. Synthetic colors show that these bandsare sensitive to effective temperature for hot stars. Our measurementswere placed on a quantitative far-ultraviolet magnitude scale byconvolving the spectra of stars observed by IUE with our cameras'spectral response functions. Fifty-eight percent of the ultravioletobjects were identified with visible stars using the SIMBAD databasewhile another 40% of the objects are blends of early type stars tooclose together to separate with our resolution. Our photometry iscompared with that from the TD-1, OAO 2, and ANS satellites and the S201(Apollo 16) far-ultraviolet camera and found to agree at the level of afew tenths of a magnitude. Unlike previous studies, almost half of theidentified visual counterparts to the ultraviolet objects are early Bstars. A plot of distance modulus against ultraviolet color excessreveals a significant population of stars with strong ultravioletexcess.
| CCD photometry and astrometry of visual double stars
We present magnitude and color differences as well as separations andposition angles of the component of 30 visual double and multiplesystems with A-type primaries measured by means of a CCD detectorattached to the 61 cm telescope on Cerro Las Campanas. The angularseparation measured using the V filter rho(V) is systematically largerthan the angular separation measured using the B filter rho(B). At least20 percent of them have very similar astrophysical parameters, but thereal separation of their components is larger than 0.01 parsecs. Thatmeans that these stars are not gravitationally bound, but they have acommon origin.
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Datos observacionales y astrométricos
| Constelación: | Altar |
| Ascensión Recta: | 17h02m52.54s |
| Declinación: | -50°09'37.3" |
| Magnitud Aparente: | 7.273 |
| Distancia: | 4545.455 parsecs |
| Movimiento Propio en Ascensión Recta: | 21.1 |
| Movimiento Propio en Declinación: | 9.6 |
| B-T magnitude: | 7.526 |
| V-T magnitude: | 7.294 |
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