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Astron. Astrophys. Suppl. Ser.
Volume 119, Number 1, October_I 1996
Page(s) 7 - 24
New weak-line T Tauri stars in Orion from the ROSAT all-sky survey DOI: 10.1051/aas:1996224

Astronomy and Astrophysics Supplement Series, Vol. 119, October 1996, 7-24

New weak-line T Tauri stars in Orion from the ROSAT all-sky survey gif

J.M. Alcalá, L. Terranegra, R. Wichmann, C. Chavarría-K., J. Krautter, J.H.M.M. Schmitt, M.A. Moreno-Corral, E. de Lara and R.M. Wagner

Send offprint requests to: J.M. Alcalá

Max-Planck-Institut für Extraterrestrische Physik, D-85740 Garching, Germany
Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy
Landessternwarte-Königstuhl, D-69117 Heidelberg, Germany
Max-Planck-Institut für Astronomie Königstuhl, D-69117 Heidelberg , Germany
Instituto de Astronomía, Ensenada B.C., México CP 22860
Lowell Observatory, 1400 West Mars Hill Road. Flagstaff, Az 86001, U.S.A.
Instituto Nacional de Astrofísica Optica y Electrónica, A.P. 51 y 216 C.P. 72000, Puebla, México

Received September 20, 1995; accepted January 26, 1996


We present results of the spectroscopic and photometric follow-up observations of the ROSAT all-sky survey in the direction of the Orion cloud complex. The main goal of these observations is the search for X-ray emitting pre-main sequence stars. 820 X-ray sources were detected with high confidence in about 450 square degrees. The mean density of X-ray sources in this region is a factor of about two higher than that of the whole RASS. 5% of the RASS sources in this region are identified with previously known and likely pre-main sequence stars. We have investigated spectroscopically 181 new RASS sources widely distributed over the entire cloud complex. On the basis of the presence of strong Li I 6707 absorption, spectral type later than F0 and chromospheric emission, 112 new weak-line T Tauri stars could be found. We present coordinates, X-ray count-rates and finding charts of the new PMS. Optical , near-infrared JHKLM and uvby- photometry for the new WTTS is also provided. In addition 24 dKe-dMe stars were also found on the basis of the RASS data.

Key words: X-rays: stars --- stars: pre-main-sequence --- ISM: Orion star forming region

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