2005/02/16 by P. Gondoin · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Stellar, planetary, and galactic studies #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.1051/0004-6361:20041991
openalex publication_date 2005/02/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
δ CrB is a single G giant whose distinctive characteristics include an X-ray luminosity exceptionally high for a slowly rotating star. δ CrB was observed in March 2003 by the observatory. The X-ray spectra of δ CrB are described by a MEKAL plasma model with two components at K and 107 K. Series of lines of highly ionized Fe and several lines of the Ly series are visible in RGS spectra, most notably from O and Ne. The oxygen abundance is similar to the average abundance of the other elements but the Ne/O ratio found for δ CrB seems higher than in the solar photosphere, reminiscent of a similar anomaly observed in a subset of solar flares and in active stellar coronae. The spectral fitting of the EPIC and RGS spectra of δ CrB suggests a corona configuration with little contribution from quiet regions similar to the Sun. On the contrary the temperature K of the “cool” plasma component is reminiscent of solar type active regions, while the hot ( K) component may be caused by disruptions of magnetic fields associated with a permanent flaring activity. The analysis results of the observation of δ CrB were compared with those of other single G giants with similar spectral type, mass and evolutionary status but with higher rotation rates. The comparison suggests that rapid rotation ( days) could increase the surface coverage with active regions and the flaring rate on G giants as expected from classical, helicity related, dynamo-driven activity. We argue that the X-ray emission of δ CrB and slowly rotating giants could be related to the existence of magnetic fields induced by turbulent motion.