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Further identification of ROSAT all-sky survey sources in Orion
We report on the identification of 22 ROSAT All-Sky Survey (RASS) X-raysources distributed in the general direction of the Orion star-formingregion. The X-ray sample contains sources from the ROSAT bright sourcecatalogue and from previous detections. The optical identifications arebased on intermediate-resolution spectroscopy and UBV Johnson photometryusing a 1m-class telescope. The strengths of the Hα , Na I D_2 andlithium lines for the stellar counterparts are evaluated applying thespectral subtraction technique, using templates of the same spectraltype. Radial velocities of the optical counterparts are also reported.Thirteen of the optical counterparts show the lithium absorption line intheir spectra and have radial velocities consistent with the Orion starforming region. Four of these objects can be classified as new bona-fideT Tauri stars.Based on observations collected at Catania Astrophysical Observatory,Italy.
| Far-ultraviolet stellar photometry: A field in Orion
Far-ultraviolet photometry for 625 objects in Orion is presented. Thesedata were extracted from electrographic camera images obtained duringsounding rocket flights in 1975 and 1982. The 1975 images were centeredclose to the belt of Orion while the 1982 images were centeredapproximately 9 deg further north. One hundred and fifty stars fell inthe overlapping region and were observed with both cameras. Sixty-eightpercent of the objects were tentatively identified with known starsusing the SIMBAD database while another 24% are blends of objects tooclose together to separate with our resolution. As in previous studies,the majority of the identified ultraviolet sources are early-type stars.However, there are a significant number for which no such identificationwas possible, and we suggest that these are interesting objects whichshould be further investigated. Seven stars were found which were brightin the ultraviolet but faint in the visible. We suggest that some ofthese are nearby white dwarfs.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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