The CARMENES search for exoplanets around M dwarfs - Radial-velocity variations of active stars in visual-channel spectra
<i>Context.<i/> Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from ~1 cm s<sup>−1<sup/> to ~1 km s<sup>−1<sup/>, depending on various stellar and activity parameters.<i>Aims.<i/> We investigate...
Gespeichert in:
| Hauptverfasser: | , , , , |
|---|---|
| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
25 June 2018
|
| In: |
Astronomy and astrophysics
Year: 2018, Jahrgang: 614 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201732362 |
| Online-Zugang: | Verlag, Volltext: https://doi.org/10.1051/0004-6361/201732362 Verlag, Volltext: https://www.aanda.org/articles/aa/abs/2018/06/aa32362-17/aa32362-17.html 
|
| Verfasserangaben: | L. Tal-Or, M. Zechmeister, A. Reiners, S.V. Jeffers, P. Schöfer, A. Quirrenbach, P.J. Amado, I. Ribas, J.A. Caballero, J. Aceituno, F.F. Bauer, V.J.S. Béjar, S. Czesla, S. Dreizler, B. Fuhrmeister, A.P. Hatzes, E.N. Johnson, M. Kürster, M. Lafarga, D. Montes, J.C. Morales, S. Reffert, S. Sadegi, W. Seifert, D. Shulyak |
| Zusammenfassung: | <i>Context.<i/> Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from ~1 cm s<sup>−1<sup/> to ~1 km s<sup>−1<sup/>, depending on various stellar and activity parameters.<i>Aims.<i/> We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1<i>μ<i/>m), which were taken within the CARMENES RV planet survey during its first 20 months of operation.<i>Methods.<i/> During this time, 287 of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric H<i>α<i/> emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence.<i>Results.<i/> Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10 m s<sup>−1<sup/> and a projected rotation velocity <i>v<i/> sin <i>i<i/> > 2 km s<sup>−1<sup/> are caused mainly by activity. We name these stars “active RV-loud stars” and find their occurrence to increase with spectral type: from ~3% for early-type M dwarfs (M0.0-2.5 V) through ~30% for mid-type M dwarfs (M3.0-5.5 V) to >50% for late-type M dwarfs (M6.0-9.0 V). Their RV-scatter amplitude is found to be correlated mainly with <i>v<i/> sin <i>i<i/>. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and H<i>α<i/> emission.<i>Conclusions.<i/> Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate. |
|---|---|
| Beschreibung: | Gesehen am 07.05.2019 |
| Beschreibung: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201732362 |