Astronomy and Astrophysics, volume 353, 1044-1054 (2000/1-3)
ROSAT PSPC observations of T Tauri stars in MBM 12.
HEARTY T., NEUHAEUSER R., STELZER B., FERNANDEZ M., ALCALA J.M., COVINO E. and HAMBARYAN V.
Abstract (from CDS):
We present the ROSAT PSPC pointed and ROSAT All-Sky Survey (RASS) observations and the results of our low and high spectral resolution optical follow-up observations of the T Tauri stars (TTS) and X-ray selected T Tauri star candidates in the region of the high galactic latitude dark cloud MBM 12 (L1453-L1454, L1457, L1458). Previous observations have revealed 3 ``classical'' T Tauri stars and 1 ``weak-line'' T Tauri star along the line of sight to the cloud. Because of the proximity of the cloud to the sun, all of the previously known TTS along this line of sight were detected in the 25ks ROSAT PSPC pointed observation of the cloud. We conducted follow-up optical spectroscopy at the 2.2-meter telescope at Calar Alto to look for signatures of youth in additional X-ray selected T Tauri star candidates. These observations allowed us to confirm the existence of 4 additional TTS associated with the cloud and at least 2 young main sequence stars that are not associated with the cloud and place an upper limit on the age of the TTS in MBM 12∼10Myr. The distance to MBM 12 has been revised from the previous estimate of 65±5pc to 65±35pc based on results of the Hipparcos satellite. At this distance MBM 12 is the nearest known molecular cloud to the sun with recent star formation. We estimate a star-formation efficiency for the cloud of 2-24%. We have also identified a reddened G9 star behind the cloud with Av∼8.4-8.9mag. Therefore, there are at least two lines of sight through the cloud that show larger extinctions (Av>5mag) than previously thought for this cloud. This higher extinction explains why MBM 12 is capable of star-formation while most other high-latitude clouds are not.
stars: formation - ISM: clouds
VizieR on-line data:
<Available at CDS (J/A+A/353/1044): table4.dat table4.ps table4.tex>
Table 4: [HNS2000] NN (Nos 1-77), [HNS2000] NNa (Nos 49a-49b, 51a-51b).
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