Open clusters or their remnants: and photometry of NGC 1901 and NGC 1252
Universidade Federal do Rio Grande do Sul, IF, CP 15051, Porto Alegre 91501-970, RS, Brazil
2 Observatorio Astronómico de Córdoba, Laprida 854, 5000, Córdoba, Argentina
Corresponding author: D. B. Pavani, firstname.lastname@example.org
Accepted: 21 May 2001
Photometry in the B and V bands is presented for the southern stellar groups NGC 1901 and NGC 1252. NGC 1901 is often described as an open cluster while NGC 1252 consists of a concentration of about 20 stars centered ≈20′ north of the original New General Catalogue coordinates, and at the southwest edge of the large region previously assigned to this object in the literature. NGC 1901 has a clear main sequence and shares similarities with the Hyades. We derive a reddening value , a distance from the Sun kpc ( kpc) and an age 0.6 ± 0.1 Gyr. NGC 1901 is conclusively a physical system, dynamically comparable to or more evolved than the Hyades. The colour-magnitude diagram of NGC 1252 suggests a turnoff and main sequence, and a total of 12 probable members. We simulated the Galactic field colour-magnitude diagram in the same direction and found it to be a poor match to NGC 1252, suggesting that NGC 1252 is not a field fluctuation. Isochrone fitting to the probable members is consistent with , kpc ( kpc) and an age 3 ± 1 Gyr. NGC 1252 cannot be ruled out as a physical group with the available data. If so, evidence is found that it is not a classical open cluster, but rather an open cluster remnant.
Key words: galaxy: open clusters and stellar associations / galaxies: individual: NGC 1901, NGC 1252
© ESO, 2001