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Cluster AgeS Experiment. CCD photometry of SX Phoenicis variables in the globular cluster M 55

Wojtek Pych·Janusz Kaluzny·Wojtek Krzeminski·A. Schwarzenberg-Czerny·Ian B. Thompson
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Abstract

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 (m-M)_V=13.86 +- 0.25 mag.

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Wojtek Pych, Janusz Kaluzny, Wojtek Krzeminski, A. Schwarzenberg-Czerny, Ian B. Thompson. 2001-01-09. Cluster AgeS Experiment. CCD photometry of SX Phoenicis variables in the globular cluster M 55. https://doi.org/10.1051/0004-6361%3A20000349

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