The CARMENES search for exoplanets around M dwarfs: Radial velocities and activity indicators from cross-correlation functions with weighted binary masks

Context. For years, the standard procedure to measure radial velocities (RVs) of spectral observations consisted in cross-correlating the spectra with a binary mask, that is, a simple stellar template that contains information on the position and strength of stellar absorption lines. The cross-corre...

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Bibliographic Details
Authors: Lafarga, M., Ribas, I., Lovis, C., Perger, M., Zechmeister, M., Bauer, F. F., Kürster, M., Cortés Contreras, M., Morales, J. C., Herrero, Enrique, Rosich, A., Baroch, D., Reiners, A., Caballero, J. A., Quirrenbach, A., Amado, P. J., Alacid, J. M., Béjar, V. J. S., Dreizler, S., Hatzes, Artie, Henning, T., Jeffers, S. V., Kaminski, A., Montes, D., Pedraz, S., Rodríguez López, C., Schmitt, H. M. M.
Format: article
Status:Published version
Publication Date:2020
Country:España
Institution:Instituto Nacional de Técnica Aeroespacial (INTA)
Repository:DIGITAL.INTA Repositorio Digital del Instituto Nacional de Técnica Aeroespacial
OAI Identifier:oai:digital.inta.es:20.500.12666/124
Online Access:https://www.aanda.org/articles/aa/full_html/2020/04/aa37222-19/aa37222-19.html
http://hdl.handle.net/20.500.12666/124
Access Level:Open access
Keyword:Methods: data analysis
Techniques: spectroscopic
Techniques: radial velocities
Stars: late-type
Stars: low-mass
Stars: activity
Description
Summary:Context. For years, the standard procedure to measure radial velocities (RVs) of spectral observations consisted in cross-correlating the spectra with a binary mask, that is, a simple stellar template that contains information on the position and strength of stellar absorption lines. The cross-correlation function (CCF) profiles also provide several indicators of stellar activity. Aims. We present a methodology to first build weighted binary masks and, second, to compute the CCF of spectral observations with these masks from which we derive radial velocities and activity indicators. These methods are implemented in a python code that is publicly available. Methods. To build the masks, we selected a large number of sharp absorption lines based on the profile of the minima present in high signal-to-noise ratio (S/N) spectrum templates built from observations of reference stars. We computed the CCFs of observed spectra and derived RVs and the following three standard activity indicators: full-width-at-half-maximum as well as contrast and bisector inverse slope. Results. We applied our methodology to CARMENES high-resolution spectra and obtain RV and activity indicator time series of more than 300 M dwarf stars observed for the main CARMENES survey. Compared with the standard CARMENES template matching pipeline, in general we obtain more precise RVs in the cases where the template used in the standard pipeline did not have enough S/N. We also show the behaviour of the three activity indicators for the active star YZ CMi and estimate the absolute RV of the M dwarfs analysed using the CCF RVs. © ESO 2020.

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