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Journal Article

The CARMENES search for exoplanets around M dwarfs. Radial-velocity variations of active stars in visual-channel spectra

MPS-Authors

Tal-Or,  L.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Zechmeister,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Reiners,  A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Jeffers,  S. V.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Schöfer,  P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Quirrenbach,  A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Amado,  P. J.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Ribas,  I.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Caballero,  J. A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Aceituno,  J.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Bauer,  F. F.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Béjar,  V. J. S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Czesla,  S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Dreizler,  S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Fuhrmeister,  B.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Hatzes,  A. P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Johnson,  E. N.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Kürster,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Lafarga,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Montes,  D.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Morales,  J. C.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Reffert,  S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Sadegi,  S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Seifert,  W.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Shulyak,  D.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

External Resource

https://ui.adsabs.harvard.edu/abs/2018A&A...614A.122T
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Citation

Tal-Or, L., Zechmeister, M., Reiners, A., Jeffers, S. V., Schöfer, P., Quirrenbach, A., et al. (2018). The CARMENES search for exoplanets around M dwarfs. Radial-velocity variations of active stars in visual-channel spectra. Astronomy and Astrophysics, 614.


Cite as: https://hdl.handle.net/21.11116/0000-0005-CAC4-A
Abstract
Context. Previous simulations predicted the activity-induced radial- velocity (RV) variations of M dwarfs to range from 1 cm s-1 to 1 km s-1, depending on various stellar and activity parameters.
Aims: We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1μm), which were taken within the CARMENES RV planet survey during its first 20 months of operation.
Methods: 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 Hα emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence.
Results: 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-1 and a projected rotation velocity v sin i > 2 km s-1 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 v sin 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 Hα emission.
Conclusions: 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. The data presented in Figs. 5 and A.1 are only available in electronic form at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/614/A122">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/614/A122</A>