IAFE   05512
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Revisiting the region of the open cluster NGC 5606
Autor/es:
ORSATTI, A.M.,FEINSTEIN, C.,VEGA E.I., VERGNE, M.M
Revista:
ASTRONOMY AND ASTROPHYSICS
Referencias:
Año: 2007 vol. 471 p. 165 - 172
ISSN:
0004-6361
Resumen:
We present polarimetric observations in the UBVRI bands corresponding to
54 stars located in the direction of NGC 5606. Our intention is to
analyze the dust characteristics between the Sun and the cluster, as
well as to confirm doubtful memberships using polarimetric tools. We
also want to determine if a group of 11 B and A stars identified in the
past by Vázquez & Feinstein (1991, A&AS, 87, 383) in
front of NGC 5606 has any physical entity. From polarimetric data we
have found at least two dust layers along the line of sight to the open
cluster. The observations show that both dust layers have their local
magnetic field with an orientation which is close to the direction of
the Galactic Plane (θ = 70.0 °), but the direction of the
polarimetric vector for the members of the cluster seems to be lower
than this value. NGC 5606 can be polarimetrically
characterized with P_max = 2.97% and θv = 63.5 °.
The internal dispersion of the polarization values for the members of
NGC 5606 seems to be compatible with intracluster dust. We were able to
add four possible new members to the list of stars in NGC 5606, and to
reject others accepted as members in past investigations; and we
identified 17 (out of the 54 observed stars) with intrinsic polarization
in their light. The group of late B- and A-type stars could be
physically related, with characteristics of an open cluster of
intermediate age (between 0.79 and 1. × 108 yr). For
this group we obtained representative values of P = 2.12% and
θv = 70.0 °. The new cluster, which we have
provisionally named Anon (La Plata 1), extends from NE to SW across the
face of NGC 5606 covering about 10'. The fitting procedure of
Schmidt-Kaler's ZAMS (1982, in Landolt/Bornstein, Neue Series VI/2b) was
used to derive the distance to the group, obtaining a distance modulus
of Vo - Mv = 9.90 (649 pc from the Sun). The mean
color excess associated with the small group is EB-V = 0.27
± 0.08 mag and the dust distribution shows great variability
across its face. We think that the small open cluster has gone
undetected due to the lack of bright member stars in it.