A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry
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We report CCD V and I time series photometry of the globular cluster NGC 6333 (M9). The technique of difference image analysis has been used, which enables photometric precision better than 0.05 mag for stars brighter than V ∼ 19.0 mag, even in the crowded central regions of the cluster. The high photometric precision has resulted in the discovery of two new RRc stars, three eclipsing binaries, seven long-term variables and one field RRab star behind the cluster. A detailed identification chart and equatorial coordinates are given for all the variable stars in the field of our images of the cluster. Our data together with the literature V-data obtained in 1994 and 1995 allowed us to refine considerably the periods for all RR Lyrae stars. The nature of the new variables is discussed. We argue that variable V12 is a cluster member and an Anomalous Cepheid. Secular period variations, double-mode pulsations and/or the Blazhko-like modulations in some RRc variables are addressed. Through the light-curve Fourier decomposition of 12 RR Lyrae stars we have calculated a mean metallicity of [Fe/H]ZW = −1.70 ± 0.01(statistical) ± 0.14(systematic) or [Fe/H]UVES = -1.67± 0.01(statistical) ± 0.19(systematic). Absolute magnitudes, radii and masses are also estimated for the RR Lyrae stars. A detailed search for SX Phe stars in the Blue Straggler region was conducted but none were discovered. If SX Phe exist in the cluster then their amplitudes must be smaller than the detection limit of our photometry. The colour–magnitude diagram has been corrected for heavy differential reddening using the detailed extinction map of the cluster of Alonso-García et al. This has allowed us to set the mean cluster distance from two independent estimates; from the RRab and RRc absolute magnitudes, we find 8.04 ± 0.19 and 7.88 ± 0.30 kpc, respectively.
Arellano Ferro , A , Bramich , D M , Figuera Jaimes , R J , Giridhar , S , Kains , N , Kuppuswamy , K , Jorgensen , U G , Alsubai , K A , Andersen , J M , Bozza , V , Browne , P , Calchi Novati , S , Damerdji , Y , Diehl , C , Dominik , M , Dreizler , S , Elyiv , A , Giannini , E , Harpsoe , K , Hessman , F V , Hinse , T C , Hundertmark , M P G , Juncher , D , Kerins , E , Korhonen , H , Liebig , C E , Mancini , L , Mathiasen , M , Penny , M T , Rabus , M , Rahvar , S , Ricci , D , Scarpetta , G , Skottfelt , J , Snodgrass , C , Southworth , J , Surdej , J , Tregloan-Reed , J , Vilela , C & Wertz , O 2013 , ' A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry ' Monthly Notices of the Royal Astronomical Society , vol 434 , no. 2 , pp. 1220-1238 . DOI: 10.1093/mnras/stt1080
Monthly Notices of the Royal Astronomical Society
© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
This project was supported by DGAPA-UNAM grant through project IN104612 and by the INDO-MEXICAN collaborative programme by DST-CONACyT. NK acknowledges an ESO Fellowship. The research leading to these results has received funding from the European Community's Seventh Framework Programme (/FP7/2007-2013/) under grant agreement No 229517. OW (aspirant FRS - FNRS), AE, YD, DR (FRIA PhD student), and J. Surdej acknowledge support from the Communauté française de Belgique – Actions de recherche concertées – Académie universitaire Wallonie-Europe. TCH gratefully acknowledges financial support from the Korea Research Council for Fundamental Science and Technology (KRCF) through the Young Research Scientist Fellowship Program. TCH acknowledges financial support from Korea Astronomy and Space Science Institute (KASI) grant number 2012-1-410-02. KA, DB, MD, MH and CL are supported by NPRP grant NPRP-09-476-1-78 from the Qatar National Research Fund (a member of Qatar Foundation). MR acknowledges support from FONDECYT post-doctoral fellowship N3120097. The Danish 1.54 m telescope is operated based on a grant from the Danish Natural Science Foundation (FNU). Funding for the Centre for Star and Planet Formation is provided by the Danish National Research Foundation. CS received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 268421. HK acknowledges support from a Marie-Curie Intra-European Fellowship.
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