2002ApJ...572..300I -
Astrophys. J., 572, 300-309 (2002/June-2)
Chandra and ASCA observations of the X-ray-brightest T Tauri stars in the ρ Ophiuchi cloud.
IMANISHI K., TSUJIMOTO M. and KOYAMA K.
Abstract (from CDS):
We present the Chandra Advanced CCD Imaging Spectrometer and ASCA Gas Imaging Spectrometer results for a series of four long-term observations on DoAr 21, ROXs 21, and ROXs 31, the X-ray-brightest T Tauri stars in the ρ Ophiuchi cloud. In the four observations with a net exposure of ∼600 ks, we found six, three, and two flares from DoAr 21, ROXs 21, and ROXs 31, respectively; hence, the flare rate is fairly high. The spectra of DoAr 21 are well fitted with a single-temperature plasma model, while those of ROXs 21 and ROXs 31 need an additional soft plasma component. Since DoAr 21 is younger (∼105 yr) than ROXs 21 and ROXs 31 (∼106 yr), these results may indicate that the soft component gradually increases as T Tauri stars age. The abundances are generally subsolar and vary from element to element. Both high first ionization potential (FIP) and low-FIP elements show enhancement over the mean abundances. An unusual giant flare is detected from ROXs 31. The peak luminosity and temperature are ∼1033 ergs.s–1 and ∼10 keV, respectively. The temperature reaches its peak value before the flux maximum and is nearly constant (4-5 keV) during the decay phase, indicating successive energy release during the flare. The abundances and absorption show dramatic variability from the quiescent to flare phase.
Abstract Copyright:
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Journal keyword(s):
Stars: Abundances - Stars: Coronae - Stars: Individual: Alphanumeric: DoAr 21 - Stars: Individual: Alphanumeric: ROX 21 - Stars: Individual: Alphanumeric: ROX 31 - Stars: Pre-Main-Sequence - X-Rays: Stars
Simbad objects:
13
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