SIMBAD references

We examine the coronal properties of the active F dwarf HR 1817. Photometric observations with EUVE show that the source is in a near-continuous state of flare-like activity. Using IUE and EUVE spectroscopic observations we construct the emission measure distribution in the 10⁴-10^7.2K temperature range. These observations reveal a hot corona and activity levels similar to those of RS CVn binaries. Based on FeXXI line ratios we derive an upper limit of 10^11.7cm^–3 for the coronal density of HR 1817 and a magnetic field strength of B≤ 160 Gauss. A comparison of the EUVE spectroscopic observations with synthetic spectra derived from ASCA and ROSAT fits, shows that optimal agreement is obtained for fits with sub-solar metal abundances. The reduced metal abundances increase the radiative losses significantly at temperatures above 10^6.5K where Fe is no longer the dominant radiative cooling agent.