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Title:
The Open Cluster NGC 7789. I. Radial Velocities for Giant Stars
Authors:
Gim, Munhwan; Hesser, James E.; McClure, Robert D.; Stetson, Peter B.
Affiliation:
AA(University of Victoria, Department of Physics and Astronomy, Victoria, BC V8W 3P6, Canada; ), AB(National Research Council, Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada; , , ), AC(National Research Council, Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada; , , ), AD(National Research Council, Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada; , , )
Publication:
The Publications of the Astronomical Society of the Pacific, Volume 110, Issue 752, pp. 1172-1182. (PASP Homepage)
Publication Date:
10/1998
Origin:
PASP
PASP Keywords:
GALAXY: OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: NGC NUMBER: NGC 7789, STARS: BINARIES: SPECTROSCOPIC, TECHNIQUES: RADIAL VELOCITIES
DOI:
10.1086/316241
Bibliographic Code:
1998PASP..110.1172G

Abstract

A total of 597 radial velocity observations for 112 stars in the ~1.6 Gyr old open cluster NGC 7789 have been obtained since 1979 with the radial velocity spectrometer at the Dominion Astrophysical Observatory. The mean cluster radial velocity is -54.9+/-0.12 km s^-1 and the dispersion is 0.86 km s^-1, from 50 constant velocity stars selected as members from this radial velocity study and the 1981 proper motion study of McNamara & Solomon. Twenty-five stars (32%) among 78 members are possible radial velocity variable stars, but no orbits are determined because of the sparse sampling. Seventeen stars are radial velocity nonmembers, while the membership estimates of six stars are uncertain. There is a hint that the observed velocity dispersion falls off at large radius. This may due to the inclusion of long-period binaries preferentially in the central area of the cluster. The known radial velocity variables also seem to be more concentrated toward the center than members with constant velocity. Although this is significant at only the 85% level, when combined with the similar result of Raboud & Mermilliod for three other clusters, the data strongly support the conclusion that mass segregation is being detected.

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