bol}$ and surface X-ray flux. The most active solar-type stars in NGC 2547 have coronal temperatures intermediate between those in the ONC and the most active older ZAMS stars. We show that simple scaling arguments predict higher coronal temperature in coronally saturated stars with lower gravities. A number of candidate flares were identified among the low-mass members and a flaring rate (for total flare energies \[0.3–3keV\] $>10^{34}$ erg) of 1 every $350^{+350}_{-120}$ks was found for solar-type stars, which is similar to rates found in the ONC and Pleiades. Comparison with [*ROSAT*]{} HRI data taken 7 years previously reveals that only 10–15 percent of solar-type stars or stars with $L_{\rm x}>3\times10^{29}$ ergs$^{-1}$ exhibit X-ray variability by more than a factor of two. This is comparable with clusters of similar age but less than in both older and younger clusters. The similar median levels of X-ray activity and rate of occurrence for large flares in NGC 2547 and the ONC demonstrate that the X-ray radiation environment around young solar-type stars remains relatively constant over their first 30Myr.
bibliography:
- 'iau\_journals.bib'
- 'master.bib'
date: Submitted October 2005
nocite:
- '[@gilliland86]'
- '[@queloz98]'
- '[@cutri03]'
- '[@jeffries04]'
- '[@naylor02]'
- '[@jeffries98n2547]'
- '[@jeffries00]'
- 