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Search for young stars among ROSAT All-Sky Survey X-ray sources in and around the R CrA dark cloud
We present the ROSAT All-Sky Survey data in a 126 deg2 areain and around the CrA star forming region. With low-resolutionspectroscopy of unidentified ROSAT sources we could find 19 new pre-mainsequence stars, two of which are classical T Tauri stars, the othersbeing weak-lined. The spectral types of these new T Tauri stars rangefrom F7 to M6. The two new classical T Tauri stars are located towardstwo small cloud-lets outside of the main CrA cloud. They appear to be ~10 Myrs old, by comparing their location in the H-R diagram withisochrones for an assumed distance of 130 pc, the distance of the mainCrA dark cloud. The new off-cloud weak-line T Tauri stars may haveformed in similar cloudlets, which have dispersed recently.High-resolution spectra of our new T Tauri stars show that they havesignificantly more lithium absorption than zero-age main-sequence starsof the same spectral type, so that they are indeed young. From thosespectra we also obtained rotational and radial velocities. For somestars we found the proper motion in published catalogs. The directionand velocity of the 3D space motion - south relative to the galaticplane - of the CrA T Tauri stars is consistent with the dark cloud beingformed originally by a high-velocity cloud impact onto the galacticplane, which triggered the star formation in CrA. We also present VRIJHKphotometry for most of the new T Tauri stars to derive theirluminosities, ages, and masses. Partly based on observations collectedat the 1.52 m and 3.5 m telescopes of the European Southern Observatory,Chile, in programs 55.E-0549, 57.E-0646, and 63.L-0023, and onobservations collected at the 0.9 m, 1.5 m, and 4.0 m CTIO telescope.
| UVBY observations of A, F, G and K field stars
Photoelectric data in the uvby system have been obtained for about 800southern stars of the Hipparcos Input Catalog (Grenon, 1982, 1985). Mostof the stars are F and G main sequence and fall in the magnitude range V= 8-11.
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