Fundamental properties of the open cluster NGC 2355

NGC 2355 is an old open cluster in the outer part of the galactic disk (l=203fdg4 , b=+11fdg8 ) which has been little studied until now. This paper presents the first astrometric and spectroscopic investigation of this cluster. We have measured precise absolute proper motions from old Carte du Ciel plates, POSS-I plates and recent CCD observations obtained with the Bordeaux meridian circle. The proper motion data reveal 38 highly probable cluster members down to B_lim = 15 mag within 7' of the cluster center. We have also obtained ELODIE high resolution spectra for 24 stars. Seventeen of them are confirmed to be members of the cluster on the basis of radial velocity. Eight of them are fast rotating turnoff stars for which the projected rotational velocity has been determined. The spectroscopic observations have also provided estimates of the physical parameters T_eff, log g, {[Fe/H]}, M_V of the 24 target stars. Two stragglers have been identified in the cluster. Combining our astrometric and spectroscopic results with previous UBV photometry and recent JHK_s photometry from the 2MASS survey we have derived the fundamental properties of the cluster: metallicity, age, distance, size, spatial velocity and orbit. Based on observations made on the 193cm telescope at the Haute-Provence Observatory, France, and on plate digitisation at the Centre d'Analyse des Images, Paris. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation.