Coronae of Young Fast Rotators
Abstract
AB Dor, Speedy Mic, and Rst 137B are in their early post-T Tauri evolutionary phase (<100 Myr), at the age of fastest rotation in the life of late-type stars. They straddle the coronal saturation-supersaturation boundary first defined by young stars in open clusters. High-resolution Chandra X-ray spectra have been analyzed to study their coronal properties as a function of coronal activity parameters Rossby number, LX/Lbol, and a coronal temperature index. Differences between stars suggest that as supersaturation is reached the DEM slope below the temperature of peak DEM becomes shallower, while the DEM drop-off above this temperature becomes more pronounced. A larger sample comprising our three targets and 22 active stars studied in the recent literature reveals a general increase of plasma at T gtrsim 107 K toward the saturated-supersaturated boundary but a decline beyond this among supersaturated stars. The coronal Fe abundances of the stellar sample are inversely correlated with LX/Lbol, declining slowly with rising LX/Lbol, but with a much more sharp decline at LX/Lbol gtrsim 3 × 10-4. For dwarfs the Fe abundance is also well correlated with Rossby number. The coronal O/Fe ratios for dwarfs show a clear increase with decreasing Rossby number, apparently reaching saturation at [O/Fe] = 0.5 at the coronal supersaturation boundary.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2008
- DOI:
- 10.1086/587611
- arXiv:
- arXiv:0802.0326
- Bibcode:
- 2008ApJ...679.1509G
- Keywords:
-
- stars: abundances;
- stars: activity;
- stars: coronae;
- Sun: corona;
- X-rays: stars;
- Astrophysics
- E-Print:
- 22 pages, 8 figures, 6 tables. Accepted by ApJ