2009ApJ...707..942H -
Astrophys. J., 707, 942-953 (2009/December-3)
X-ray emission and corona of the young intermediate-mass binary θ1 Ori E.
HUENEMOERDER D.P., SCHULZ N.S., TESTA P., KESICH A. and CANIZARES C.R.
Abstract (from CDS):
θ1 Ori E is a young, moderate mass binary system, a rarely observed case of spectral-type G-giants of about 3 solar masses, which are still collapsing toward the main sequence, where they presumably become X-ray faint. We have obtained high-resolution X-ray spectra with Chandra and find that the system is very active and similar to coronal sources, having emission typical of magnetically confined plasma. It has a broad temperature distribution with a hot component and significant high energy continuum; narrow emission lines from H- and He-like ions, as well as a range of Fe ions, and relative luminosity, Lx/Lbol= 10–3, at the saturation limit. Density, while poorly constrained, is consistent with the low density limits, our upper limits being ne< 1013/cm3 for Mg XI and ne< 1012/cm3 for Ne IX. Coronal elemental abundances are sub-solar, with Ne being the highest at about 0.4 times solar. We find a possible trend in Trapezium hot plasmas toward low relative abundances of Fe, O, and Ne, which is hard to explain in terms of the dust depletion scenarios of low-mass young stars. Variability was unusually low during our observations relative to other coronally active stars. Qualitatively, the emission is similar to post-main-sequence G-stars. Coronal structures could be compact or comparable to the dimensions of the stellar radii. From comparison to X-ray emission from similar mass stars at various evolutionary epochs, we conclude that the X-rays in θ1 Ori E are generated by a convective dynamo, present during contraction, but which will vanish during the main-sequence epoch possibly to be resurrected during post-main-sequence evolution.
Abstract Copyright:
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Journal keyword(s):
stars: coronae - stars: individual: tet01 Ori E - stars: pre-main sequence - X-rays: stars
Simbad objects:
15
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