ASCA Observations of the T Tauri Star SU Aurigae and the Surrounding L1517 Dark Cloud
Abstract
We present the results of a ~40 ks pointed ASCA observation of the L1517 star-forming region, centered on the X-ray-bright T Tauri star SU Aurigae. This star has the highest X-ray luminosity of any classical T Tauri star in the Taurus-Auriga region, and its optical spectra show evidence for both mass inflow and outflow.
Strong X-ray emission was detected from SU Aur (Lx = 1030.9 ergs s-1) as well as weaker emission from five other pre-main-sequence stars. Although no large-amplitude flares were detected, the X-ray emission of SU Aur showed clear variability in the form of a slow decline in count rate during the 1.3 day observation. We provide the first direct comparison of the coronal differential emission measure (DEM) distribution of a classical T Tauri star with that of a young main-sequence star of similar spectral type. The DEM distributions of SU Aur (G2; age 3 Myr) and the young solar-like star EK Draconis (G0 V; age 70 Myr) are qualitatively similar, with both showing a bimodal temperature distribution characterized by a cool plasma component peaking at ~8-9 MK and a hot component peaking at ~20-21 MK. However, there is a striking difference in the relative proportion of plasma at high temperatures in the two stars, with hot plasma (>=20 MK) accounting for ~80% of the volume emission measure of SU Aur, compared to only ~40% in EK Dra. These results provide new insight into the changes that will occur in the corona of a T Tauri star as it descends onto the main sequence. A sharp decline in the fraction of coronal plasma at flarelike temperatures will occur during the late-T Tauri and post-T Tauri phases, and other recent X-ray studies have shown that this decline will continue after the young solar-like star reaches the main sequence.- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1998
- DOI:
- 10.1086/306532
- Bibcode:
- 1998ApJ...509..761S
- Keywords:
-
- ISM: INDIVIDUAL (L1517);
- STARS: CORONAE;
- STARS: INDIVIDUAL (HD 282624 );
- STARS: INDIVIDUAL ( SU AUR);
- STARS: PRE-MAIN-SEQUENCE;
- X-RAYS: STARS;
- ISM: individual (L1517);
- Stars: Coronae;
- stars: individual (HD 282624 );
- stars: individual ( SU Aur);
- Stars: Pre-Main-Sequence;
- X-Rays: Stars