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Search for Variables in the Galactic Globular Clusters NGC 6544 and NGC 6642

Published online by Cambridge University Press:  15 February 2018

Martha L. Hazen
Martha L. Hazen*
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA

Extract

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A search for variable stars in the globular cluster NGC 6544 has revealed only one possible short period variable within the tidal radius of the cluster. A search in NGC 6642 yielded 16 new RR Lyrae stars within the tidal radius and 5 new field RRs. The previously discovered (Hoffleit 1972) V1 is a slow variable, and V2 is an RR Lyrae star. Photometry of the variables within the tidal radius gives a mean B for the horizontal branch of < B > = 17.0 mag. With E(B – V) = 0.37 mag and (B – V) = 0.35 mag for RR Lyraes, a value for V(HB) = 16.3 mag is derived. This is about one mag fainter than previous estimates (Webbink 1985), and places NGC 6642 at a distance of approximately 7.9 kpc.

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 337
Copyright
Copyright © Cambridge University Press 1993

References

Hoffieit, D., 1972, IBVS No. 660.Google Scholar
Webbink, R.F., 1985, in: Dynamics of Star Clusters, eds. Goodman, J. and Hut, P., Reidel, Dordrecht, p 541.Google Scholar