Revisiting the region of the Open Cluster NGC 5606

ANA M. ORSATTI; CARLOS FEINSTEIN; E. IRENE VEGA; M. MARCELA VERGNE

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2007 vol. 471 p. 165 - 172

0004-6361

We present polarimetric observations in the UBVRI bands correspondingto 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 want also to analyze if a groupof 11 B and A stars identified in the pastby V´azquez & Feinstein (1991) in front of NGC 5606 has any physical entity.From polarimetric data we have found at least two dust layers along the line ofsight 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 ($ heta=70dg0$), but the direction of the polarimetric vector for the members of the cluster seems tobe lower than this value. object{NGC 5606} can be polarimetrically characterized with $ P_{max}$ = 2.97% and$ heta_{v}$ = 63$dg$5. The internal dispersion of the polarization values for the members of NGC 5606seems to be compatible with intracluster dust.We have been able to add four possible new members to the list of stars in NGC 5606, and to reject others accepted asmembers in past investigations; and we could identify 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 intermediateage (between 0.79 and $ 1. 10^8$ yr). We obtained for this group representative values of $P=$2.12% and $ heta_{v}$= 70$dg$9.The new cluster, which we have provisionally named Anon (La Plata 1), extends from NE to SW across the face of NGC 5606 covering about 10$´$.The fitting procedure of Schmidt-Kaler´s ZAMS (cite{SK82}) was used to derive the distance to the group, obtaining a distance modulus of $ V_{o} - M_{v}$ = 9.90 (649 pc from the Sun). The mean color excess associated to the small group is$ E_{B-V} = 0.27 pm $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.