Digging in the coronal graveyard - A ROSAT observation of the red giant Arcturus

Abstract

view Abstract Citations (47) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Digging in the Coronal Graveyard: A ROSAT Observation of the Red Giant Arcturus Ayres, Thomas R. ; Fleming, Thomas A. ; Schmitt, Juergen H. M. M. Abstract A deep exposure of the bright star Arcturus (Alpha Bootis: K1 III) with the Roentgensatellit (Rosat) failed to detect soft X-ray emission from the archetype 'noncoronal' red giant. The 3-sigma upper limit in the energy band 0.1-2.4 keV corresponds to an X-ray luminosity of less than 3 x 10 to the 25th erg/s, equivalent to a coronal surface flux density of less than 0.0001 solar. The nondetection safely eliminates coronal irradiation as a possible mechanism to produce the highly variable He I 10830 feature and emphasizes the sharp decline in solarlike coronal activity that accompanies the evolution of low-mass single stars away from the main sequence. While the most conspicuous object in the Rosat field of view was not visible in X-rays, at least one fainter star is among the about 60 sources recorded: the Sigma Sct variable CN Boo, an A8 giant in the UMa Stream. Publication: The Astrophysical Journal Pub Date: August 1991 DOI: 10.1086/186099 Bibcode: 1991ApJ...376L..45A Keywords: Red Giant Stars; Stellar Coronas; X Ray Sources; Hertzsprung-Russell Diagram; Rosat Mission; Stellar Luminosity; Astrophysics; STARS: CORONAE; STARS: INDIVIDUAL CONSTELLATION NAME: ALPHA BOOTIS; STARS: INDIVIDUAL CONSTELLATION NAME: CN BOOTIS; STARS: X-RAYS full text sources ADS | data products SIMBAD (5) HEASARC (1)