Simultaneous eROSITA and TESS observations of the ultra-active star AB~Doradus

Abstract

We present simultaneous multiwavelength observations of the ultra-active star AB~Doradus obtained in the X-ray range with the eROSITA instrument on board the Russian--German Spectrum-Roentgen-Gamma mission (SRG), and in the optical range obtained with the Transiting Exoplanet Survey Satellite (TESS). Thanks to its fortuitous location in the vicinity of the southern ecliptic pole, AB~Dor was observed by these missions simultaneously for almost 20 days. With the hitherto obtained data we study the long-term evolution of the X-ray flux from AB~Dor and the relation between this observable and the photospheric activity of its spots. Over the 1.5 years of eROSITA survey observations, the "quiescent" X-ray flux of AB~Dor has not changed, and furthermore it appears unrelated to the photospheric modulations observed by TESS. During the simultaneous eROSITA and TESS coverage, an extremely large flare event with a total energy release of at least 4 $\times$ 10${}^{36}$ erg in the optical was observed, the largest ever seen on AB~Dor. We show that the total X-ray output of this flare was far smaller than this, and discuss whether this maybe a general feature of flares on late-type stars.

arXiv commentTo appear on A&A, Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission

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Cited by in corpus (4)

• The eROSITA Final Equatorial-Depth Survey (eFEDS): The variability catalogue and multi-epoch comparison
• Simultaneous X-ray and optical variability of M dwarfs observed with eROSITA and TESS
• Large-scale structures in the stellar wind of fast-rotating stars spawned by the presence of Earth-like planets
• Nearby Young Stars and Young Moving Groups