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| Paper: |
The Contribution of Flares to Transition Region Heating in Active G and K Dwarfs |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1560 |
| Authors: |
Saar, S. H.; Bookbinder, J. A. |
| Abstract: |
We present the preliminary results of an analysis of HST GHRS rapid readout spectra covering the region 1380 AA - 1670 AA for two active dwarfs of approximately Pleiades age: HD 129333 (G0V, P_rot ~2.8 days) and LQ Hya (K2V, P_rot ~1.6 days). Both were observed for >= 4 orbits at 1 second time resolution (total exposure time > 13,000 s each). The time series of the transition region (TR) fluxes (the sum of C iv + Si iv) shows many low-level flares in both stars, making the quiescent level somewhat difficult to identify. We assume that TR heating in the stars is a combination of a steady background (due to e.g., MHD wave heating) plus superimposed flares. The distribution of TR photons per unit time, N(n_TR), should thus have a component at the low counts which can be fit by a Poisson function. The best-fit Poisson to the low count end of N(n_T) then defines the the average background TR heating rate (from the Poisson mean), and an upper limit to the total steady heating unaffected by flares (from the Poisson amplitude). Our analysis suggests that at least 8% of TR flux of HD 129333 and 11% of TR flux of LQ Hya arose from flares during our observations. We also discuss the flare rates as a function of energy. This represents the first detailed information on flare heating rates for active G and K dwarfs. |
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