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Astron. Astrophys. 353, 1044-1054 (2000)

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ROSAT PSPC observations of T Tauri stars in MBM12 *

T. Hearty 1, R. Neuhäuser 1, B. Stelzer 1, M. Fernández 1, J.M. Alcalá 2, E. Covino 2 and V. Hambaryan 3

1 Max-Planck-Institut für Extraterrestrische Physik, 85740 Garching, Germany
2 Osservatorio Astronomico di Capodimonte, 80131 Napoli, Italy
3 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

Received 25 May 1999 / Accepted 22 October 1999

Abstract

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 MBM12 (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 25 ks 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 MBM12 [FORMULA] 10 Myr.

The distance to MBM12 has been revised from the previous estimate of [FORMULA] pc to [FORMULA] pc based on results of the Hipparcos satellite. At this distance MBM12 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 [FORMULA] [FORMULA] 8.4-8.9 mag. Therefore, there are at least two lines of sight through the cloud that show larger extinctions ([FORMULA] [FORMULA] 5 mag) than previously thought for this cloud. This higher extinction explains why MBM12 is capable of star-formation while most other high-latitude clouds are not.

Key words: stars: formation – ISM: clouds

* Table 4 is only available in electronic form at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/353/1044 (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgibin/qcat?J/A+A/353/1044 .

Send offprint requests to: T. Hearty (thearty@xray.mpe.mpg.de)

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© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000
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