Journal Article

A proper motion study of the globular cluster M55

K. Zloczewski, J. Kaluzny and I. B. Thompson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 3711-3718
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI:
A proper motion study of the globular cluster M55

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We have derived the absolute proper motion (PM) of the globular cluster M55 using a large set of CCD images collected with the du Pont telescope between 1997 and 2008. We find (μα cos δ, μδ) = (−3.31 ± 0.10, −9.14 ± 0.15) mas yr−1 relative to background galaxies. Membership status was determined for 16 945 stars with 14 < V < 21 from the central part of the cluster. The PM catalogue includes 52 variables, of which 43 are probable members of M55. This sample not only is dominated by pulsating blue straggler stars, but also includes five eclipsing binaries, three of which are main-sequence objects. The survey also identified several candidate blue, yellow and red straggler stars belonging to the cluster. We detected 15 likely members of the Sgr dSph galaxy located behind M55. The average PM for these stars was measured to be (μα cos δ, μδ) = (−2.23 ± 0.14, −1.83 ± 0.24) mas yr−1.

Keywords: astrometry; binaries: eclipsing; blue stragglers; globular clusters: individual: NGC 6809 (M55); galaxies: individual: Sagitarrius dSph

Journal Article.  4346 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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