Searching for variable stars in the cores of five metal-rich globular clusters using EMCCD observations

Globular clusters: individual; Instrumentation: high angular resolution; Stars: variables: general; Stars: variables: RR lyrae; Giant stars; Time series analysis; Difference images; Globular clusters; Hubble space telescopes; Instrumentation:high angular resolution; Red giant branches; Stars

Abstract :

[en] Aims. In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal-rich ([Fe/H] > -1) globular clusters: NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652. The data have been used to perform a census of the variable stars in the central parts of these clusters. Methods. The observations were made with the electron-multiplying charge-couple device (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile, and they were analysed using difference image analysis to obtain high-precision light curves of the variable stars. Results. It was possible to identify and classify all of the previously known or suspected variable stars in the central regions of the five clusters. Furthermore, we were able to identify and, in most cases, classify 48, 49, 7, 8, and 2 previously unknown variables in NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652, respectively. Especially interesting is the case of NGC 6441, for which the variable star population of about 150 stars has been thoroughly examined by previous studies, including a Hubble Space Telescope study. In this paper we are able to present 49 new variable stars for this cluster, of which one (possibly two) are RR Lyrae stars, two are W Virginis stars, and the rest are long-period semi-regular or irregular variables on the red giant branch. We have also detected the first double-mode RR Lyrae in the cluster. © ESO 2015.

Disciplines :

Space science, astronomy & astrophysics

Author, co-author :

Skottfelt, J.; Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, København Ø, Denmark, Centre for Star and Planet Formation, Natural History Museum, University of Copenhagen, Østervoldgade 5-7, København K, Denmark

Bramich, D. M.; Qatar Environment and Energy Research Institute, Qatar Foundation, Tornado Tower, Floor 19, PO Box 5825, Doha, Qatar

Figuera Jaimes, R.; European Southern Observatory, Karl-Schwarzschild-Straße 2, Garching bei München, Germany, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St Andrews, United Kingdom

Jørgensen, U. G.; Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, København Ø, Denmark, Centre for Star and Planet Formation, Natural History Museum, University of Copenhagen, Østervoldgade 5-7, København K, Denmark

Kains, N.; European Southern Observatory, Karl-Schwarzschild-Straße 2, Garching bei München, Germany, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, United States

Arellano Ferro, A.; Instituto de Astronomía, Universidad Nacional Autónomade Mexico, Mexico, Mexico

Alsubai, K. A.; Qatar Environment and Energy Research Institute, Qatar Foundation, Tornado Tower, Floor 19, PO Box 5825, Doha, Qatar

Bozza, V.; Dipartimento di Fisica E. R. Caianiello, Università di Salerno, via Giovanni Paolo II 132, Fisciano (SA), Italy, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Napoli, Italy

Calchi Novati, S.; Dipartimento di Fisica E. R. Caianiello, Università di Salerno, via Giovanni Paolo II 132, Fisciano (SA), Italy, NASA Exoplanet Science Institute, MS 100-22, California Institute of Technology, Pasadena, CA, United States, Istituto Internazionale Per Gli Alti Studi Scientifici (IIASS), Vietri Sul Mare (SA), Italy

Ciceri, S.; Max Planck Institute for Astronomy, Königstuhl 17, Heidelberg, Germany

More authors (24 more)

Language :

English

Title :

Searching for variable stars in the cores of five metal-rich globular clusters using EMCCD observations

Publication date :

2015

Journal title :

Astronomy and Astrophysics

ISSN :

0004-6361

eISSN :

1432-0746

Publisher :

EDP Sciences

Volume :

573

Peer reviewed :

Peer Reviewed verified by ORBi

Funders :

DNRF - Danish National Research Foundation
NASA - National Aeronautics and Space Administration
NSCF - National Natural Science Foundation of China

Available on ORBi :

since 15 January 2018

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