Document 
| Abstract | PDF (1.07 MB) | PS (765 KB) | References | HTML | Online Material | Tables at CDS | Simbad Objects | NASA ADS Abstract Service |
Free access article
A&A 426, 819-826 (2004)
DOI: 10.1051/0004-6361:20041332
New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach
L. Balaguer-Núñez1, 2, 3, C. Jordi1, 4, D. Galadí-Enríquez5 and J. L. Zhao21 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona, Spain
e-mail: Lola.Balaguer@am.ub.es
2 Shanghai Astronomical Observatory, CAS Shanghai 200030, PR China
3 Institute of Astronomy, Madingley Road, CB3 OHA Cambridge, UK
4 CER for Astrophysics, Particle Physics and Cosmology, associated with Instituto de Ciencias del Espacio-CSIC
5 Centro de Astrobiología (CSIC-INTA), Carretera de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
(Received 21 May 2004 / Accepted 5 July 2004 )
Abstract
We have calculated proper motions and re-evaluated the membership
probabilities of 810 stars in the area of two NGC objects,
NGC 1817 and NGC 1807. We have obtained
absolute proper motions from 25 plates in the reference system of
the Tycho-2 Catalogue.
The plates
have a maximum epoch difference of 81 years; and they were taken
with the double astrograph at Zô-Sè station of Shanghai
Observatory, which has an aperture of 40 cm
and a plate scale of 30´´ mm
-1. The average proper motion
precision is 1.55 mas yr
-1. These proper motions are used to
determine the membership probabilities of stars in the region,
based on there being only
one very extended physical cluster: NGC 1817.
With that aim, we have applied and compared parametric and
non-parametric approaches to cluster/field segregation.
We have obtained a list of 169 probable member stars.
Key words: Galaxy: open clusters and associations: individual: NGC 1817 -- Galaxy: open clusters and associations: individual: NGC 1807 -- astrometry -- methods: data analysis
SIMBAD Objects
Tables at the CDS
© ESO 2004