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Ultraviolet-selected Field and Pre-main-sequence Stars Toward Taurus and Upper Scorpius
We have carried out a Galaxy Evolution Explorer (GALEX) Cycle 1 guestinvestigator program covering 56 deg2 near the Taurus Tassociation and 12 deg2 along the northern edge of the UpperScorpius OB association. We combined photometry in the GALEXfar-ultraviolet and near-ultraviolet bands with data from the Two MicronAll Sky Survey to identify candidate young (lsim100 Myr old) stars asthose with an ultraviolet excess relative to older main-sequence stars.Follow-up spectroscopy of a partial sample of these candidates suggestsfive new members of Taurus, with 8-20 expected from additionalobservations, and five new members of Upper Scorpius, with three to sixexpected from additional observations. These candidate new membersappear to represent a distributed, non-clustered population in eitherregion, although our sample statistics are as of yet too poor toconstrain the nature or extent of this population. Rather, our studydemonstrates the ability of GALEX observations to identify young stellarpopulations distributed over a wide area of the sky. We also highlightthe necessity of a better understanding of the Galactic ultravioletsource population to support similar investigations. In particular, wereport a large population of stars with an ultraviolet excess but nooptical indicators of stellar activity or accretion, and briefly argueagainst several interpretations of these sources.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| 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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