Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry
Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry
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DOI：
10.1051/0004-6361/201321819
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发表时间：
2013-05
影响因子：
6.5
通讯作者：
N. Kains;D. Bramich;A. Ferro;R. F. Jaimes;R. Jaimes;U. Jørgensen;U. Jørgensen;S. Giridhar;
中科院分区：
文献类型：
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作者：
N. Kains;D. Bramich;A. Ferro;R. F. Jaimes;R. Jaimes;U. Jørgensen;U. Jørgensen;S. Giridhar;
目标。我们给出了球状星团M30(NGC7099)从2011年到2012年的26个夜晚的V和I时间序列观测的分析。我们使用我们的数据来搜索这个星系团中的变星，并精炼已知变量的周期；然后我们使用我们的可变星光曲线来推导出该星系团的参数值。方法：研究方法。我们利用差分图像分析方法对数据进行了归约，得到了高精度的变星光线曲线。然后，我们通过对天琴座RR恒星的光曲线进行傅里叶分解来估计星团参数，这可能是一个好的周期估计。我们还通过将理论等时线与我们的颜色-星等图(CMD)进行拟合，得出了该星系团的年龄估计。结果。在之前被编入变星目录的13颗恒星中，我们发现只有4颗是真正的变星。我们发现了两个新的天琴座RR变星，并从文献中确认了另外两个候选的天琴座RR变星。我们还探测到了其他四个新的变星，包括一个日食蓝散星系统和一颗SX土卫二恒星。我们对天琴座RR星的光曲线进行傅里叶分解，利用经验关系得到星团参数。我们发现团簇金属丰度[Fe/H](ZW)=-2.01+/-0.04，或[Fe/H](UVES)=-2.11+/-0.06，距离为8.32+/-0.20kpc(使用RR0变量)、8.10kpc(使用一个RR1变量)和8.35+/-0.42kpc(使用我们在M30中的SX Phoenicis星探测)。将等时线与CMD进行拟合，我们估计M30的年龄为13.0+/-1.0Gyr。
Aims. We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive values for the cluster's parameters. Methods. We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. We also derive an estimate for the age of the cluster by fitting theoretical isochrones to our colour-magnitude diagram (CMD). Results. Out of 13 stars previously catalogued as variables, we find that only 4 are bona fide variables. We detect two new RR Lyrae variables, and confirm two additional RR Lyrae candidates from the literature. We also detect four other new variables, including an eclipsing blue straggler system, and an SX Phoenicis star. This amounts to a total number of confirmed variable stars in M 30 of 12. We perform Fourier decomposition of the light curves of the RR Lyrae stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H](ZW) = -2.01 +/- 0.04, or [Fe/H](UVES) = -2.11 +/- 0.06, and a distance of 8.32 +/- 0.20 kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35 +/- 0.42 kpc (using our SX Phoenicis star detection in M 30). Fitting isochrones to the CMD, we estimate an age of 13.0 +/- 1.0 Gyr for M 30.