ROSAT-HRI detection of the Class I protostar YLW16A in the ρ Ophiuchi dark cloud
Abstract
I analyze unpublished or partially published archival ROSAT data of the rho Ophiuchi dark cloud. This set of seven overlapping ROSAT HRI pointings, composed of eight ~ one-hour exposures, detects mainly the X-ray brightest T Tauri stars of this star-forming region. Only two HRI sources are new X-ray sources, and their optical counterparts are proposed as new Weak T Tauri star candidates. Meanwhile the ROSAT HRI caught during just one exposure a weak X-ray source ({cal L}=10; SNR=4.1 sigma for Gaussian statistics) among a group of three embedded young stellar objects including two Class I protostars. Previous ROSAT PSPC, ASCA GIS observations, and as I argue here one Einstein IPC observation, have already detected an X-ray source in this area, but this higher angular resolution data show clearly that X-rays are emitted by the Class I protostar YLW16A. This is the second Class I protostar detected by the ROSAT HRI in this dark cloud. The determination of the intrinsic X-ray luminosity of this event, L_X[0.1{-2.4 keV]}=(9.4-450) 1030 erg s-1, critically depends on the source absorption estimate. Improvements will be obtained only by the direct determination of this parameter from fitting of Chandra and XMM-Newton spectra.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- April 2001
- DOI:
- 10.1051/0004-6361:20010325
- arXiv:
- arXiv:astro-ph/0103013
- Bibcode:
- 2001A&A...370L..22G
- Keywords:
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- OPEN CLUSTERS AND ASSOCIATION: RHO OPH;
- STARS: PRE-MAIN SEQUENCE;
- X-RAYS: STARS;
- INFRARED: STARS;
- Astrophysics
- E-Print:
- 4 pages, 2 figures, 2 tables. Accepted for publication in A&