Volume 367, Number 1, February III 2001
|Page(s)||148 - 158|
|Section||Interstellar and circumstellar matter|
|Published online||15 February 2001|
Cluster AgeS Experiment. CCD photometry of SX Phoenicis variables in the globular cluster M 55
Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warszawa, Poland
2 Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA
3 Astronomical Observatory of Adam Mickiewicz University, ul. Sloneczna 36, 60-286 Poznan, Poland
Corresponding author: W. Pych,firstname.lastname@example.org
Accepted: 27 November 2000
We present CCD photometry of SX Phe variables in the field of the globular cluster M 55. We have discovered 27 variables, three of which are probable members of the Sagittarius dwarf galaxy. All of the SX Phe stars in M 55 lie in the blue straggler region of the cluster color-magnitude diagram. Using period ratio information we have identified the radial pulsation modes for one of the observed variables. Inspection of the period-luminosity distribution permits the probable identifications of the pulsation modes for most of the rest of the stars in the sample. We have determined the slope of the period-luminosity relation for SX Phe stars in M 55 pulsating in the fundamental mode. Using this relation and the HIPPARCOS data for SX Phe itself, we have estimated the apparent distance modulus to M 55 to be mag.
Key words: globular clusters: individual: M 55 / (stars): blue stragglers: stars: variables: δ Sct / stars: oscillations / stars: population II
© ESO, 2001
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