Ruprecht 1: a Small, Moderately Young Open Cluster in the Third Galactic Quadrant

PIATTI, A. E.; CLARIÁ, J. J.; PARISI, M. C.; AHUMADA, A. V.

Baltic Astronomy

Institute of Theoretical Physics and Astronomy

Lugar: Vilnius, Lithuania; Año: 2008 vol. 17 p. 67 - 77

1392-0049

We present CCD observations in the Washington system C and T1 passbands down to T1 ˜ 18.5 in the field of Ruprecht 1, a poorly studied open cluster located in the third Galactic quadrant. We measured T1 magnitudes and C-T1 colors for a total of 862 stars distributed throughout an area of 13.6 × 13.6 arcmin. The cluster turned out to be very small; its linear radius being 2.6 ± 0.2 pc, as estimated from star counts in appropriate-sized boxes distributed throughout the entire field observed. By fitting the zero-age main sequence to the T1 vs. C-T1 color-magnitude diagram, we derive EB-V = 0.25 ± 0.05, independently from the cluster´s metallicity. Our analysis suggests that Ruprecht 1 is moderately young. In fact, adopting the theoretical metal contents Z = 0.02 and 0.008, which provide the best global fits, we derive heliocentric distances of d = 1.9 ± 0.4 kpc and 1.5 ± 0.3 kpc and ages of 200 ± 47 Myr and 251 ± 58 Myr in each case.