A Caltech Library Service

What is the second parameter - The anomalous globular cluster NGC 7006

Cohen, Judith G. and Frogel, Jay A. (1982) What is the second parameter - The anomalous globular cluster NGC 7006. Astrophysical Journal, 255 . L39-L43. ISSN 0004-637X. doi:10.1086/183765.

[img] PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


An infrared color-magnitude diagram for NGC 7006 and moderate dispersion digital optical spectra of eight of its members indicate a metal abundance of -1.5 dex with respect to the sun. However, the ratio of red to blue horizontal-branch stars is quite large and is what would be expected for a cluster of much higher metallicity. Molecular band strengths are determined for CO in four stars, and CH and CN in five stars, and it is found that none of these molecular bands are anomalously strong compared to the same molecular features in other globulars of similar metallicity but varying horizontal-branch type. This is contrary to the behavior predicted if the C, N, and O abundances are the 'second parameter' needed to explain anomalous horizontal-branch morphologies.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cohen, Judith G.0000-0002-8039-4673
Additional Information:© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1981 October 19; accepted 1981 December 9. Cerro Tololo Inter-American Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under National Science Foundation contract AST 78-27879. We thank Jay Elias for assistance in obtaining some of these data and Ann Rosenthal for assistance in reducing the SIT frames. J. G. C. is grateful for time allocated on the du Pont telescope of the Mount Wilson and Las Campanas Observatory.
Funding AgencyGrant Number
NSFAST 78-27879
Subject Keywords:clusters: globular — galaxies: Milky Way
Record Number:CaltechAUTHORS:20190531-091632044
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95982
Deposited By: George Porter
Deposited On:03 Jun 2019 14:46
Last Modified:16 Nov 2021 17:17

Repository Staff Only: item control page