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Far-Ultraviolet Observations of the Ophiuchus Region with SPEAR
We present the first far-ultraviolet (FUV; 1370-1670 Å) image ofthe Ophiuchus molecular cloud region, observed with the SPEAR imagingspectrograph. The flux levels of the diffuse FUV continuum are inreasonable agreement with those of the Voyager observations in theshorter FUV wavelengths (912-1216 Å), provided that the diffuseFUV emission is dominated by the spectra from late O- and early B-typestars. The observed region of the present study was divided into fivesubregions according to their FUV intensities, and the spectrum wasobtained for each subregion with prominent H2 fluorescentemission lines. A synthetic model of the H2 fluorescentemission indicates that the molecular cloud has more or less uniformphysical parameters over the Ophiuchus region, with a hydrogen densitynH of 500 cm-3 and a H2 column densityN(H2) of 2×1020 cm-2. It isnotable that the observed diffuse FUV continuum is well reproduced by asingle-scattering model with scattered starlight from the dust cloudlocated at ~120-130 pc, except at a couple of regions with high opticaldepth. The model also gives reasonable properties of the dust grains ofthe cloud with an albedo a of 0.36+/-0.20 and a phase function asymmetryfactor g of 0.52+/-0.22.
| 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.
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Osservazione e dati astrometrici
| Costellazione: | Ofiuco |
| Ascensione retta: | 16h28m45.53s |
| Declinazione: | -17°59'06.0" |
| Magnitudine apparente: | 7.178 |
| Distanza: | 156.006 parsec |
| Moto proprio RA: | 18.7 |
| Moto proprio Dec: | -7.1 |
| B-T magnitude: | 7.482 |
| V-T magnitude: | 7.204 |
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