RT Journal Article T1 Empirical calibration of the near-infrared CaII triplet - III. Fitting functions A1 Cenarro, A. J. A1 Gorgas García, Francisco Javier A1 Cardiel López, Nicolás A1 Vazdekis, A. A1 Peletier, R. F. AB Using a near-infrared stellar library of 706 stars with a wide coverage of atmospheric parameters, we study the behaviour of the Call triplet strength in terms of effective temperature, surface gravity and metallicity. Empirical fitting functions for recently defined line-strength indices, namely CaT*, CaT and PaT, are provided. These functions can be easily implemented into stellar population models to provide accurate predictions for integrated Ca II strengths. We also present a thorough study of the various error sources and their relation to the residuals of the derived fitting functions. Finally, the derived functional forms and the behaviour of the predicted Ca II are compared with those of previous works in the field. PB Wiley SN 0035-8711 YR 2002 FD 2002-02-01 LK https://hdl.handle.net/20.500.14352/59506 UL https://hdl.handle.net/20.500.14352/59506 LA eng NO This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2002 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. The authors are indebted to the referee G. Da Costa for useful comments and suggestions. JC acknowledges the Comunidad de Madrid for a Formación de Personal Investigador fellowship. AV acknowledges the support of the PPARC rolling grant ‘Extragalactic Astronomy and Cosmology in Durham 1998-2002’. This research has made use of the NASA’s Astrophysics Data System Article Service. This work was supported by the Spanish Programa Sectorial de Promoción del Conocimiento (PB96-610) and Programa Nacional de Astronomía y Astrofísica (AYA2000-977) and, in part, by a British Council grant within the British/Spanish Joint Research Programme (Acciones Integradas). NO PPARC rolling grant Extragalactic Astronomy and Cosmology NO Spanish Programa Sectorial de Promoción del Conocimiento NO Programa Nacional de Astronomía y Astrofísica NO British Council NO British/Spanish Joint Research Programme (Acciones Integradas) DS Docta Complutense RD 9 abr 2025