Observations and detectability of young Suns’ flaring and CME activity in optica
Insights
The history of the Sun continues to be an area of keen interest in modern astrophysics. At present, there remains a dearth of observationally constrained data on CME rates from young solar analogues, necessitating dedicated monitoring efforts. A comprehensive three-year study involving medium-resolution optical spectroscopic monitoring of a select group of bright solar analogues was carried out using the 0.5m telescope at the Lustbühel Graz Observatory (OLG) of the University of Graz, Austria. Our primary objective was the identification of flares and CMEs within the obtained spectra. Over a monitoring period spanning more than 1700 hours, we succeeded in detecting four flares and one filament eruption on the star EK Dra, thereby extending the previously reported data. However, no discernible activity signatures were observed in the remaining stars. For these instances, we were able to establish upper limits on the occurrence rates of significantly massive CMEs, detectable within our observational setup, ranging from 0.1 to 2.2 events per day. Notably, we also evaluated the detectability of flares/CMEs in OLG spectra by leveraging solar 2D Hα spectra from the MEES solar observatory. Our findings indicate the inobservability of solar-sized events within our dataset. In a hypothetical scenario, we demonstrated the detectability of solar events at an equivalent fractional active region area of 18% in residual spectra and 72% in equivalent width time series on the star HN Peg.
Abstract
Introduction
Conclusion
References
The Sun’s history is still a subject of interest to modern astrophysics. Observationally constrained CME rates of young solar analogues are still lacking, as those require dedicated monitoring. We present medium resolution optical spectroscopic monitoring of a small sample of bright and prominent solar analogues over a period of three years using the 0.5m telescope at observatory Lustbühel Graz (OLG) of the University of Graz, Austria. The aim is the detection of flares and CMEs from those spectra. In more than 1700 hours of spectroscopic monitoring we found signatures of four flares and one filament eruption on EK Dra which has been reported in previous literature, but we complementarily extended the data to cover the latter phase. The other stars did not reveal detectable signatures of activity. For these non-detections we derive upper limits of occurrence rates of very massive CMEs, which are detectable with our observational setup, ranging from 0.1 to 2.2 day−1 , but these may be even smaller than the given rates considering observational biases. Furthermore, we investigate the detectability of flares/CMEs in OLG spectra by utilizing solar 2D Hα spectra from MEES solar observatory. We find that solar-sized events are not detectable within our observations. By scaling up the size of the solar event, we show that with a fractional active region area of 18% in residual spectra and 72% in equivalent width time series derived from the same residuals that solar events are detectable if they had hypothetically occurred on HN Peg.