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Radial-velocity (RV) jitter caused by stellar magnetic activity is animportant factor in state-of-the-art exoplanet discovery surveys such asCARMENES. Stellar rotation, along with heterogeneities in the photosphere andchromosphere caused by activity, can result in false-positive planetdetections. Hence, it is necessary to determine the stellar rotation period andcompare it to any putative planetary RV signature. Long-term measurements ofactivity indicators such as the chromospheric emission in the Ca II H&K linesenable the identification of magnetic activity cycles. In order to determinestellar rotation periods and study the long-term behavior of magnetic activityof the CARMENES guaranteed time observations (GTO) sample, it is advantageousto extract Ca II H&K time series from archival data, since the CARMENESspectrograph does not cover the blue range of the stellar spectrum containingthe Ca II H&K lines. We have assembled a catalog of 11634 archival spectra of186 M dwarfs acquired by seven different instruments covering the Ca II H&Kregime: ESPADONS, FEROS, HARPS, HIRES, NARVAL, TIGRE, and UVES. The relativechromospheric flux in these lines was directly extracted from the spectra byrectification with PHOENIX synthetic spectra via narrow passbands around the Caii H&K line cores. The combination of archival spectra from various instrumentsresults in time series for 186 stars from the CARMENES GTO sample. As anexample of the use of the catalog, we report the tentative discovery of threepreviously unknown activity cycles of M dwarfs. We conclude that the method ofextracting Ca II H&K fluxes with the use of model spectra yields consistentresults for different instruments and that the compilation of this catalog willenable the analysis of long-term activity time series for a large number of Mdwarfs.

CARMENES input catalog of M dwarfs VI. A time-resolved Ca II H&K catalog from archival data