Coronal and chromospheric emission from cool stars in near-simultaneous ROSAT all-sky survey and Mount Wilson data ?

Mt. WilsonCa II HK a similar trend, but with substantially larger scatter, is also present for evolved stars. A comparison between values from different passbands of the Mt. Wilson HK spectrophotometer shows that relatively hot stars((B V ) 0:50)appeartohaveaCa IIlinecoreemission peak about a factor 2 to 3 wider than cooler stars.