Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...447..342p&link_type=abstract
Astrophysical Journal v.447, p.342
Astronomy and Astrophysics
Astronomy
3
Stars: Emission-Line, Be, Stars: Flare, Stars: Pre-Main-Sequence, X-Rays: Stars
Scientific paper
We use low-resolution, broadband optical spectroscopy and high-resolution X-ray imaging to continue the study of X-ray sources in the Orion star formation region about 1° south of the Trapezium. We identify 10 new M and K pre-main-sequence (PM S) stars as X-ray sources. At least eight and perhaps all have emission lines. Two stars, V942 and V988 Ori, show evidence for Hα equivalent-width variability. Emission-line PMS (ePMS) stars including both classical (CTTS) and weak-lined T Tauri stars (WTTS) obey the relation between X-ray luminosity and stellar luminosity, Lx (ergs s-1) = 2.2 × 108L0.67*. The X-ray emission thus tracks the total stellar emission, probably through the dependence of both on stellar surface area, as has been suggested before. Higher mass PMS stars show a similar but flatter dependence of Lx on L* . For TTS the average value of Lx/L* = 1.78 × 10-3. We also detect the integrated X-ray emission from an ensemble of optically fainter stars that may be located deeper in the cluster. The X-ray observations continue to show that the inventory of X-ray sources at a given detection limit stays almost constant over a period of ≥ 10 yr. The probability that a star in this sample flares in X-rays with greater than a factor of ˜2 increase in average intensity for any ˜5000 s observation is constrained to be <10%.
Angelini Lorella
Pravdo Steven Howard
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