ASCA X-ray spectra of the active single stars β Ceti and π¹ Ursae Majoris

Abstract

We present X-ray spectra obtained by ASCA of two single, active stars, the G dwarf π¹ UMa, and the G9/K0 giant βCet. The spectra of both stars require the presence of at least two plasma components with different temperatures, 0.3-0.4 keV and ~0.7 keV, in order for acceptable fits to be obtained. The spectral resolving power and signal-to-noise ratio of the solid state imaging spectrometer (SIS) spectra allow us to formally constrain the coronal abundances of a number of elements. In β Cet, we find Mg to be overabundant, while other elements such as O, Ne, and N are underabundant, relative to the solar photospheric values. From the lower signal-to-noise ratio SIS spectrum of π¹ UMa, we find evidence for underabundances of O, Ne, and Fe. These results are discussed in the context of the present understanding of elemental abundances in solar and stellar coronae.