A census of variability in globular cluster M 68 (NGC 4590)

	A census of variability in globular cluster M 68 (NGC 4590)
	Kains, N ; Ferro, AA ; Jaimes, RF ; Bramich, DM ; Skottfelt, J ; Jorgensen, UG ; Tsapras, Y ; Street, RA ; Browne, P ; Dominik, M
刊名	ASTRONOMY & ASTROPHYSICS
	2015-06
卷号	578
关键词	stars: variables: RR Lyrae stars: variables: general globular clusters: individual: M 68
ISSN号	0004-6361
通讯作者	Kains, N (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA.
产权排序	第十七完成单位
英文摘要	Aims. We analyse 20 nights of CCD observations in the V and I bands of the globular cluster M 68 (NGC 4590) and use them to detect variable objects. We also obtained electron-multiplying CCD (EMCCD) observations for this cluster in order to explore its core with unprecedented spatial resolution from the ground. Methods. We reduced our data using difference image analysis to achieve the best possible photometry in the crowded field of the cluster. In doing so, we show that when dealing with identical networked telescopes, a reference image from any telescope may be used to reduce data from any other telescope, which facilitates the analysis significantly. We then used our light curves to estimate the properties of the RR Lyrae (RRL) stars in M 68 through Fourier decomposition and empirical relations. The variable star properties then allowed us to derive the cluster's metallicity and distance. Results. M68 had 45 previously confirmed variables, including 42 RRL and 2 SX Phoenicis (SX Phe) stars. In this paper we determine new periods and search for new variables, especially in the core of the cluster where our method performs particularly well. We detect 4 additional SX Phe stars and confirm the variability of another star, bringing the total number of confirmed variable stars in this cluster to 50. We also used archival data stretching back to 1951 to derive period changes for some of the single-mode RRL stars, and analyse the significant number of double-mode RRL stars in M68. Furthermore, we find evidence for double-mode pulsation in one of the SX Phe stars in this cluster. Using the different classes of variables, we derived values for the metallicity of the cluster of [Fe/H] = -2.07 +/- 0.06 on the ZW scale, or -2.20 +/- 0.10 on the UVES scale, and found true distance moduli mu(0) = 15.00 +/- 0.11 mag (using RR0 stars), 15.00 +/- 0.05 mag (using RR1 stars), 14.97 +/- 0.11 mag (using SX Phe stars), and 15.00 +/- 0.07 mag (using the M-V-[Fe/H] relation for RRL stars), corresponding to physical distances of 10.00 +/- 0.49, 9.99 +/- 0.21, 9.84 +/- 0.50, and 10.00 +/- 0.30 kpc, respectively. Thanks to the first use of difference image analysis on time-series observations of M 68, we are now confident that we have a complete census of the RRL stars in this cluster.
学科主题	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	Astronomy & Astrophysics
关键词[WOS]	RR-LYRAE STARS ; LARGE-MAGELLANIC-CLOUD ; SX-PHOENICIS STARS ; HORIZONTAL-BRANCH STARS ; DIFFERENCE IMAGE-ANALYSIS ; TIME-SERIES PHOTOMETRY ; HUBBLE-SPACE-TELESCOPE ; VARIABLE-STARS ; METAL ABUNDANCES ; CCD PHOTOMETRY
收录类别	SCI ; EI
原文出处	http://www.aanda.org/articles/aa/abs/2015/06/aa24600-14/aa24600-14.html
语种	英语
WOS记录号	WOS:000357502600140
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/6808]
专题	云南天文台_系外行星研究组云南天文台_中国科学院天体结构与演化重点实验室
作者单位	1.Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 2.European Southern Observatory, Karl-Schwarzschild Straße 2, 85748 Garching bei München, Germany 3.Instituto de Astronomía, Universidad Nacional Autónoma de Mexico, 04310 Coyoácan, Mexico 4.SUPA School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK 5.Qatar Environment and Energy Research Institute, Qatar Foundation, Tornado Tower, Floor 19, PO Box 5825, Doha, Qatar 6.Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen, Denmark 7.Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5, 1350 Copenhagen, Denmark 8.Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA 9.School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK 10.Qatar Foundation, PO Box 5825, Doha, Qatar
推荐引用方式 GB/T 7714	Kains, N,Ferro, AA,Jaimes, RF,et al. A census of variability in globular cluster M 68 (NGC 4590)[J]. ASTRONOMY & ASTROPHYSICS,2015,578.
APA	Kains, N.,Ferro, AA.,Jaimes, RF.,Bramich, DM.,Skottfelt, J.,...&Wertz, O.(2015).A census of variability in globular cluster M 68 (NGC 4590).ASTRONOMY & ASTROPHYSICS,578.
MLA	Kains, N,et al."A census of variability in globular cluster M 68 (NGC 4590)".ASTRONOMY & ASTROPHYSICS 578(2015).