RADIAL VELOCITIES IN THE REGION OF CR 135

Abstract

ABSTRACT Continuing our work on radial velocities in some open cluster fields in the Southern hemisphere, we give mean radial velocities of 63 stars belonging to a 2 degree x 2 degree field centered on Cr 135 in Puppis, where only a few radial velocities of bright stars are at present known. The plates have been taken with the 40-cm Objective prism of ESO at La Silla, in Chile, and measured at the Observatoire de Haute-Porvence, in France, with a cross-correlation method. The dispersion of the instrument is 110 A mm-1. We obtained relative radial velocities which have been fitted to the IAU standard system of radial velocities by means of some stars with already known radial velocities. We present the histogram of the errors and a general radial velocity diagram, as well as a discussion about the possible variable stars and the cluster membership. The histogram of the errors E =sqrt[(sum(epsilon2))/(N(N-1))] shows a maximum between E=2.0 and E=3.0 km s-1 for an average of 6 plates per star. The general radial velocity diagram has a peak at about 20 km s-1 representing principally the field stars. The radial velocities of the five brightest stars and those of stars previously selected as probable cluster members lie in this peak. On the basis of photometric data, the physical reality of Cr 135 has been contested. Our results show that if, nevertheless, the cluster exists, its radial velocity is very close to that of field stars. Cr 135 could also belong to an old association or to a stellar group.