We report the observations of X-ray oscillations during the flare in a cool active star ξ Boo for the first time. ξ Boo was observed by EPIC/MOS of XMM-Newton satellite. The X-ray light curve is investigated with wavelet and periodogram analyses. Both analyses clearly show oscillations of the period of ∼ 1019 s. We interpret these oscillations as a fundamental fast-kink mode of magnetoacoustic ...

Direct comparison of high-resolution X-ray spectra of the active dMe star AD Leo, observed three times with Chandra, shows variability of key density-sensitive lines, possibly due to flaring activity. In particular, a significant long-duration enhancement of the coronal density is indicated by the Ne IX and Si XIII He-like triplets, and possibly also by density-sensitive Fe XXI line ratios. Sub...