Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter



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Martínez Arnáiz, R. and Maldonado, J. and Montes Gutiérrez, David and Eiroa, C. and Montesinos, B. (2010) Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter. Astronomy & Astrophysics, 520 . ISSN 0004-6361

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Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star.
Aims. We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca II H & K lines, to others that hold noteworthy advantages.
Methods. We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF ECHELLE package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R’_HK index.
Results. We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to estimate the expected RV jitter for the active stars in the sample.

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© ESO, 2010.
Based on observations made with the 2.2 m telescope at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto (Spain) and the Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Istituto Nazionale de Astrofisica Italiano (INAF), in the Spanish Observatorio del Roque de los Muchachos. This research has been supported by the Programa de Acceso a Infraestructuras Científicas y Tecnológicas Singulares (ICTS).
R. Martínez-Arnáiz acknowledges support from the Spanish Ministerio de Educación y Ciencia (currently the Ministerio de Ciencia e Innovación), under the grant FPI20061465-00592 (Programa Nacional Formación Personal Investigador) and projects AYA2008-00695 (Programa Nacional de Astronomía y Astrofísica), AYA2008-01727 (Programa Nacional de Astronomía y Astrofísica), AstroMadrid S2009/ESP-1496. This research has made use of the SIMBAD database and VizieR catalogue access tool, operated at CDS, Strasbourg, France. We also thank the anonymous referee for his/her valuable suggestions on how to improve the manuscript.

Uncontrolled Keywords:CA-II-H; Multiwavelength optical observations; Sun-like stars; Main-sequence stars; Low-mass stars; Magnetic activity; Stellar-activity; Binary-systems; Cool stars; Echelle spectrograph
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:37826
Deposited On:24 May 2016 15:36
Last Modified:10 Dec 2018 15:05

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