Complete X-ray census of M dwarfs in the solar neighborhood
- Autor(en)
- M. Caramazza, B. Stelzer, E. Magaudda, St Raetz, M. Güdel, S. Orlando, K. Poppenhäger
- Abstrakt
Context. X-ray emission is the most sensitive diagnostic of magnetic activity in M dwarfs and, hence, of the dynamo in low-mass stars. Moreover it is crucial for quantifying the influence of the stellar irradiation on the evolution of planet atmospheres. Aims. We have embarked in a systematic study of the X-ray emission in a volume-limited sample of M dwarf stars to explore the full range of activity levels present in their coronae. We look to obtain a better understanding of the conditions in their outer atmospheres and their possible impact on the circumstellar environment. Methods. Based on a recent catalog of Gaia objects within 10 pc from the Sun, we identified all its stars with spectral types between M0 and M4 and we carried out a systematic search for X-ray measurements of this sample. To this end, we used both archival data from ROSAT, XMM-Newton, and the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission, as well as our own dedicated XMM-Newton observations. To make inferences on the properties of the M dwarf corona, we compared the range of their observed X-ray emission levels to the flux radiated by the Sun from different types of magnetic structures: coronal holes, background corona, active regions, and cores of active regions. In this work, we focus on the properties of stars with the faintest X-ray emission. Results. At the current state of our project, with more than 90% of the 10 pc M dwarf sample observed in the X-ray, there is only one star that has had no detections: GJ 745 A. With an upper limit luminosity of log Lx (erg s-1) < 25.4 and an X-ray surface flux of log FX,SURF (erg cm-2 s-1) < 3.6, GJ 745 A defines the lower boundary of the X-ray emission level for M dwarfs. Together with its proper motion companion (GJ 745 B), it is the only star in this volume-complete sample located in the range of X-ray surface flux that corresponds to the faintest solar coronal structures, namely: coronal holes. The fact that the ultra-low X-ray emission level of GJ 745 B (log Lx (erg s-1) = 25.6 and log FX,SURF (erg cm-2 s-1) = 3.8) is entirely attributed to flaring activity indicates that while its corona is dominated by holes, at least one magnetically active structure is present. This structure determines the total X-ray brightness and the coronal temperature of the star.
- Organisation(en)
- Institut für Astrophysik
- Externe Organisation(en)
- Eberhard Karls Universität Tübingen, INAF-Osservatorio Astrofisico di Torino, Leibniz-Institut für Astrophysik Potsdam, Universität Potsdam
- Journal
- Astronomy and Astrophysics
- Band
- 676
- Anzahl der Seiten
- 11
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361/202346470
- Publikationsdatum
- 08-2023
- Peer-reviewed
- Ja
- ÖFOS 2012
- 103003 Astronomie, 103004 Astrophysik
- Schlagwörter
- ASJC Scopus Sachgebiete
- Astronomy and Astrophysics, Space and Planetary Science
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/fdc11e26-4e73-4d8e-8bee-33d8718bc6af