%0 Generic %1 talor2018carmenes %A Tal-Or, L. %A Zechmeister, M. %A Reiners, A. %A Jeffers, S. V. %A Schöfer, P. %A Quirrenbach, A. %A Amado, P. J. %A Ribas, I. %A Caballero, J. A. %A Aceituno, J. %A Bauer, F. F. %A Béjar, V. J. S. %A Czesla, S. %A Dreizler, S. %A Fuhrmeister, B. %A Hatzes, A. P. %A Johnson, E. N. %A Kürster, M. %A Lafarga, M. %A Montes, D. %A Morales, J. C. %A Reffert, S. %A Sadegi, S. %A Seifert, W. %A Shulyak, D. %D 2018 %K mdwarf multiplicity %T The CARMENES search for exoplanets around M dwarfs: Radial-velocity variations of active stars in visual-channel spectra %U http://arxiv.org/abs/1803.02338 %X Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from $\sim1$ cm/s to $\sim1$ km/s, depending on various stellar and activity parameters. 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$$\mu$m), which were taken within the CARMENES RV planet survey during its first $20$ months of operation. During this time, $287$ of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric H$\alpha$ emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Despite having a median number of only $11$ measurements per star, we show that the RV variations of the stars with RV scatter of $>10$ m/s and a projected rotation velocity $v i>2$ km/s are caused mainly by activity. We name these stars `active RV-loud stars' and find their occurrence to increase with spectral type: from $\sim3\%$ for early-type M dwarfs (M$0.0$$-$$2.5$V) through $\sim30\%$ for mid-type M dwarfs (M$3.0$$-$$5.5$V) to $>50\%$ for late-type M dwarfs (M$6.0$$-$$9.0$V). Their RV-scatter amplitude is found to be correlated mainly with $v i$. 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$\alpha$ emission. 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.

@misc{talor2018carmenes, abstract = {Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from $\sim1$ cm/s to $\sim1$ km/s, depending on various stellar and activity parameters. 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$$\mu$m), which were taken within the CARMENES RV planet survey during its first $20$ months of operation. During this time, $287$ of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric H$\alpha$ emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Despite having a median number of only $11$ measurements per star, we show that the RV variations of the stars with RV scatter of $>10$ m/s and a projected rotation velocity $v \sin{i}>2$ km/s are caused mainly by activity. We name these stars `active RV-loud stars' and find their occurrence to increase with spectral type: from $\sim3\%$ for early-type M dwarfs (M$0.0$$-$$2.5$V) through $\sim30\%$ for mid-type M dwarfs (M$3.0$$-$$5.5$V) to $>50\%$ for late-type M dwarfs (M$6.0$$-$$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 H$\alpha$ emission. 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.}, added-at = {2018-03-08T15:09:52.000+0100}, author = {Tal-Or, L. and Zechmeister, M. and Reiners, A. and Jeffers, S. V. and Schöfer, P. and Quirrenbach, A. and Amado, P. J. and Ribas, I. and Caballero, J. A. and Aceituno, J. and Bauer, F. F. and Béjar, V. J. S. and Czesla, S. and Dreizler, S. and Fuhrmeister, B. and Hatzes, A. P. and Johnson, E. N. and Kürster, M. and Lafarga, M. and Montes, D. and Morales, J. C. and Reffert, S. and Sadegi, S. and Seifert, W. and Shulyak, D.}, biburl = {https://www.bibsonomy.org/bibtex/2058d100ae85084091934c5dce033009d/superjenwinters}, description = {The CARMENES search for exoplanets around M dwarfs: Radial-velocity variations of active stars in visual-channel spectra}, interhash = {44f49c19325260aa151022a568af7291}, intrahash = {058d100ae85084091934c5dce033009d}, keywords = {mdwarf multiplicity}, note = {cite arxiv:1803.02338Comment: A&A accepted}, timestamp = {2018-03-08T15:09:52.000+0100}, title = {The CARMENES search for exoplanets around M dwarfs: Radial-velocity variations of active stars in visual-channel spectra}, url = {http://arxiv.org/abs/1803.02338}, year = 2018 }