Multi-Mode Oscillations in Classical Cepheids and RR Lyrae-Type Stars
Paweł Moskalik
我回顾了不同类型的多模脉动中观察到的经典造父变星和天琴座RR型星。介绍集中在最新的结果，特别强调最近检测到的非径向振荡。
I review different types of multi-mode pulsations observed in classical Cepheids and in RR Lyrae-type star. The presentation concentrates on the newest results, with special emphasis on recently detected nonradial oscillations.
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We present new large samples of Galactic Cepheids and RR Lyrae stars from the OGLE Galaxy Variability Survey.
RR Lyraes and Type II Cepheids in the Magellanic Clouds: Distance Scales and Population Gradients
本文讨论了目前在天琴座RR型变星光度定标中的不确定度。利用从天琴座RR型星和经典造父变星得到的SMC和LMC之间距离模的差异，估算了金属丰度对造父变星PL（VI）关系的影响为0.29 ± 0.11 mag/dex。有证据表明，RR型天琴座变星和II型造父变星有着共同的K-log（P）关系。金属丰度和年龄梯度的LMC讨论的RR天琴座变星和AGB星的数据。
Distance determination from the Cepheids and RR Lyrae period-luminosity relations
造父变星和天琴座RR型星是距离标度工作中重要的脉动变星，因为它们是标准烛光。造父变星遵循定义明确的周期光度（PL）关系，定义为从光学到中红外（MIR）的波段。另一方面，RR型天琴座星在近红外和中红外波段也表现出光致发光关系。在这篇文章中，我们回顾了造父变星和RR型天琴座星的PL关系的一些最新进展和校准。对于造父变星，我们讨论了通过银河系和大麦云云路线的PL关系的校准。对于RR型天琴座星，我们总结了最近在发展MIR PL关系方面的一些工作。
Multi-Periodic Oscillations in Cepheids and RR Lyrae-Type Stars
经典的造父变星和天琴座RR型星通常被认为是纯径向、严格周期的变星。然而，并非所有的变量都符合这一简单的图景。在这篇综述中，我讨论了在造父变星和天琴座RR星中观察到的不同形式的多周期性，包括Blazhko效应和各种类型的径向和非径向多模振荡。
X-ray properties of RR Lyrae and Cepheid variables from eROSITA
研究利用eROSITA数据发现RR型天琴座和造父变星的X射线对应物，指出RR型天琴座可能首次观测到此类恒星的X射线发射，并揭示了造父变星X射线光度与脉动周期的关系。
Classical variables like RR Lyrae, classical and Type-II Cepheids and Mira variables all follow period-luminosity relations that make them interesting as distance indicators. Especially the RR Lyrae and delta Cepheids are crucial in establishing the distance scale in the Universe, and all classes of variables can be used as tracers of galactic structure. I will present an overview of recent period-luminosity relations and review the work that has been done using the Gaia DR1 data so far, and discuss possibilities for the future
Classical Cepheid and RR Lyrae variables are fundamental tracers of cosmic distances and stellar evolution and pulsation. Light curve analysis and pulsation properties of these radially pulsating stars provide stringent tests for theoretical evolution and pulsation models. I discuss a detailed light curve analysis of classical Cepheid variables in the Galaxy and the Magellanic Clouds at multiple wavelengths. The variation of light curve parameters as a function of period, wavelength and metallicity is quantified to constrain the theoretical parameters, such as, the mass-luminosity relations ob…
Analysis of the possible Blazhko-effect Cepheid V473 Lyrae
天琴座V473是一颗特殊的造父变星，具有强烈的振幅调制，类似于在天琴座RR型恒星中观察到的布拉日科效应。我们收集了几个调制周期的数据，并开始了详细的分析。第一个结果表明，该恒星显示出振幅和相位调制的平均周期为1204天，但无论是周期长度和调制的强度受到相当大的变化。一个可能的五重组分的傅立叶光谱和额外的周期变化也被检测到。
Cepheids and RR Lyrae stars in the K2 fields
随着K2任务的逐步凝视方法，开普勒将能够观察到大量的造父变星和天琴座RR星。在本文中，我们描述了目标选择的努力，并根据K2两轮工程测试数据的第一印象。我们还总结了开普勒可以实现的科学目标，包括对各种附加模式和Blazhko效应的理解，人口研究以及在选定活动中观察河外恒星的可能性。
Period Changes of Mira Variables, RR Lyrae Stars, and Type II Cepheids
Mira变星、天琴座RR变星和II型造父变星都代表了低质量恒星的演化状态，长期的观测表明，每一类变星的脉动周期都会发生变化。大多数米拉变星的周期变化很小或没有变化，但也有少数变星的周期变化很大，这可能与渐近红巨星分支上的热脉冲有关。个别的天琴座RR型星的周期变化与恒星演化理论的预测不一致。这对于表现出Blazhko效应的天琴座RR型恒星来说尤其如此。然而，球状星团内所有天琴座RR型变星的平均周期变化证明了进化理论预测的更好但仍不完美的匹配。观测到的短周期II型造父变星（BL Her星）和长周期II型造父变星（W Vir星）的周期变化与它们通过不稳定带的演化运动预期的周期变化率大致一致。
Empirical Period-Color and Amplitude-Color Relations for Classical Cepheids and RR Lyrae Variables
我们分析了银河系，大麦云和小麦哲伦云造父变星和RR天琴座变量的周期颜色（PC）和振幅颜色（AC）图在最大和最小光的阶段。我们从文献中汇编了银河系造父变星$V$和$I$波段的数据。我们利用OGLE-III巡天观测的麦哲伦云造父变星和天琴座RR变星的光学波段光变曲线数据。我们应用$F$ -统计检验来检查造父变星PC和AC关系斜率的任何变化的显著性。周期大于7天的造父变星在最大光照下的PC关系较浅，相应的AC关系在整个周期范围内都是平坦的。对于基本模式造父变星在麦哲伦云，我们发现显着的休息PC和AC的关系在最大和最小的光周期约10天。麦哲伦云在最大光照下的PC关系对于周期大于10天的造父变星来说是平坦的。第一次泛音造父变星的周期小于2.5天有一个浅的PC关系在最低光。对于基本模式RR天琴座，我们确认早期的工作支持一个平面PC关系在最小的光和振幅和颜色之间的显着关系在最大的光。我们发现，不存在这样的关系的第一泛音RR天琴座星。这些发现与恒星光球/氢电离前沿相互作用的考虑是一致的。这些非线性可以为恒星脉动和演化的模型提供强有力的约束。
Square root two period ratios in Cepheid and RR Lyrae variable stars
我们记录了一些造父变星和天琴座RR型变星的存在，这些变星具有以前未被认识的特征。这些恒星表现出主脉动除以次脉动的周期比P1/P2非常接近sqrt（2）的性质。这些类型的其他恒星的周期比没有显示出与一个密切的协会和一个单一的显着的非调和数集群。仔细检查发现，这些恒星的偏差为几倍~0.06%。这种偏离似乎以约0.000390（4）的离散阶跃存在，表明在这种振荡中可能存在一种精细结构。
Gaia Data Release 1 contains parallaxes for more than 700 Galactic Cepheids and RR Lyrae stars, computed as part of the Tycho-Gaia Astrometric Solution (TGAS). We have used TGAS parallaxes, along with literature ($V, I, J, {K_\mathrm{s}}, W_1$) photometry and spectroscopy, to calibrate the zero point of the Period-Luminosity and Period-Wesenheit relations of classical and type II Cepheids, and the near-infrared Period-Luminosity, Period-Luminosity-Metallicity and optical Luminosity-Metallicity relations of RR Lyrae stars. In this contribution we briefly summarise results obtained by fitting th…
V473 Lyrae, a unique second-overtone Cepheid with two modulation cycles
V473天琴座是唯一一颗被确认具有周期性振幅和相位变化的造父变星，类似于在天琴座RR型恒星中观察到的Blazhko效应。我们收集了所有可用的光度数据和一些径向速度测量，以调查调制的性质。光度和径向速度振幅的比较证实了恒星在第二泛音中脉动。广泛的数据集，跨越40多年，使我们能够检测到一个次级调制周期约为5300天或14.5年。也可以在初级调制的周期中检测次级变化。在现象学上，光的变化类似于Blazhko效应。为了找到物理联系，我们计算了线性流体动力学模型来搜索可以驱动调制的潜在模式共振，并在第二泛音和其他模式之间发现了两个可行的半整数（n：2）和三个n：4共振。如果这些共振中的任何一个将被非线性模型证实，它可能会证实模式共振模型，这是一种共同的机制，可以驱动天琴座RR和造父变星的调制。
The Gaia second Data Release (DR2) presents a first mapping of full-sky RR Lyrae stars and Cepheids observed by the spacecraft during the initial 22 months of science operations. The Specific Object Study (SOS) pipeline, developed to validate and fully characterise Cepheids and RR Lyrae stars (SOS Cep&RRL) observed by Gaia, has been presented in the documentation and papers accompanying the Gaia first Data Release. Here we describe how the SOS pipeline was modified to allow for processing the Gaia multiband (G, G_BP and G_RP) time series photometry of all-sky candidate variables and produce sp…
Continuous, high-precision photometry from space revolutionized many fields of stellar astrophysics, and that extends to the well-studied families of RR Lyrae and Cepheid variable stars as well. After the pioneering work of MOST, the CoRoT and Kepler missions released an avalanche of discoveries. We found signals that needed exquisite precision, such as an abundance of additional modes and granulation. Other discoveries, like period doubling, simply needed us to break away from the day-night cycle of the Earth. And the future holds more possibilities, with the BRITE, K2, and Gaia missions at f…
We present results from a comparative study of light curves of Cepheid and RR Lyrae stars in the Galaxy and the Magellanic Clouds with their theoretical models generated from the stellar pulsation codes. Fourier decomposition method is used to analyse the theoretical and the observed light curves at multiple wavelengths. In case of RR Lyrae stars, the amplitude and Fourier parameters from the models are consistent with observations in most period bins except for low metal-abundances ($Z<0.004$). In case of Cepheid variables, we observe a greater offset between models and observations for both …
We discuss time-series analyses of classical Cepheid and RR Lyrae variables in the Galaxy and the Magellanic Clouds at multiple wavelengths. We adopt the Fourier decomposition method to quantify the structural changes in the light curves of Cepheid and RR Lyrae variables. A quantitative comparison of Cepheid Fourier parameters suggests that the canonical mass-luminosity models that lie towards the red-edge of the instability strip show a greater offset with respect to observations for short-period Cepheids. RR Lyrae models are consistent with observations in most period bins. We use ensemble l…
The second data release of the Gaia mission includes an advance catalog of variable stars. The classification of these stars are based on sparse photometry from the first 22 months of the mission. We set out to investigate the purity and completeness of the all-sky Gaia classification results with the help of the continuous light curves of the observed targets from the Kepler and K2 missions, focusing specifically on RR Lyrae and Cepheid pulsators, outside the Galactic Bulge region. We crossmatched the Gaia identifications with the observations collected by the Kepler space telescope. We inspe…
Blazhko effect in Cepheids and RR Lyrae stars
Blazhko效应是20世纪初发现的对天琴座RR型恒星脉动的显著幅度和相位调制。由于空间测光任务提供了长时间、不间断、超精确的时间序列数据，这种神秘调制的研究领域最近得到了扩展。在本文中，我简要概述了与Blazhko效应有关的新观测结果，如极端调制，不规则调制周期和附加周期。我认为，这些发现加上专门的地面工作，现在为我们提供了一个相当完整的图片和一个很好的起点，理论研究。事实上，在Blazhko RR型天琴座恒星中已经发现了新的、无法预测的动力学现象，如倍周期、高阶共振、三模脉动和低维混沌。这导致了对这个百年之谜的新解释，即径向模式之间的高阶共振。沿着这些思路，我提出了最新的努力和进展，从理论的角度来看。最后讨论了造父变星的振幅变化。
Period-colour and amplitude-colour (PCAC) relations can be used to probe both the hydrodynamics of outer envelope structure and evolutionary status of Cepheids and RR Lyraes. In this work, we incorporate the PCAC relations for RR Lyraes, BL Her, W Vir and classical Cepheids in a single unifying theory that involves the interaction of the hydrogen ionization front (HIF) and stellar photosphere and the theory of stellar evolution. PC relations for RR Lyraes and classical Cepheids using OGLE-IV data are found to be consistent with this theory: RR Lyraes have shallow/sloped relations at minimum/ma…
We present a machine learning method to estimate the physical parameters of classical pulsating stars such as RR Lyrae and Cepheid variables based on an automated comparison of their theoretical and observed light curve parameters at multiple wavelengths. We train artificial neural networks (ANNs) on theoretical pulsation models to predict the fundamental parameters (mass, radius, luminosity, and effective temperature) of Cepheid and RR Lyrae stars based on their period and light curve parameters. The fundamental parameters of these stars can be estimated up to 60 percent more accurately when …
The separation between RR Lyrae (RRLs) and Type II Cepheid (T2Cs) variables based on their period is debated. Both types of variable stars are distance indicators and we aim to promote the use of T2Cs as distance indicators in synergy with RRLs. We adopted new and existing optical and Near-Infrared (NIR) photometry of \wcen~to investigate several diagnostics (colour-magnitude diagram, Bailey diagram, Fourier decomposition of the light curve, amplitude ratios) for their empirical separation. We found that the classical period threshold at 1 day is not universal and does not dictate the evolutio…
We present the final release of the OGLE collection of classical pulsators (Cepheids and RR Lyr stars) in the Large and Small Magellanic Clouds. The sky coverage has been increased from 670 to 765 square degrees compared to the previous edition of the collection. We also add some Cepheids and RR Lyr stars found by the Gaia team and reclassify three Cepheids. Ultimately, our collection consists of 9650 classical Cepheids, 343 type II Cepheids, 278 anomalous Cepheids, and 47828 RR Lyr stars inside and toward the Magellanic System.
Globular clusters are both primary fossils of galactic evolution and formation and are ideal laboratories for constraining the evolution of low-mass and metal-poor stars. RR Lyrae and type II Cepheid variables are low-mass, radially pulsating stars that trace old-age stellar populations. These stellar standard candles in globular clusters are crucial for measuring their precise distances and, in turn, absolute ages, and for the calibration of the extragalactic distance scale. Herein, the evolutionary stages of RR Lyrae and type II Cepheids are discussed, and their pulsation properties, includi…
Three dimensional maps of the Magellanic Clouds using RR Lyrae Stars and Cepheids II. The Small Magellanic Cloud
我们使用光学引力透镜实验（OGLE III）调查的变星数据来确定小麦哲伦云（SMC）的三维结构。推导出个人的距离RR天琴座恒星和造父变星，我们调查这些示踪剂的老和年轻的人口在SMC的分布。光度估计的金属丰度被用来确定1494 RR天琴座恒星的距离，这些恒星的典型年龄大于9 Gyr。对于2522颗造父变星，年龄在几十到几百万年之间，距离是用它们的周期光度关系计算的。从每个恒星的固有颜色的个人红化估计用于获得高精度的三维地图。天琴座RR型星和造父变星的距离非常吻合。天琴座RR型恒星的平均距离为61.5 +/- 3.4 kpc。造父变星的平均距离为63.1 +/- 3.0 kpc。这两个星群都显示出扩展的星盘高度，其中天琴座RR星为2.0 +/- 0.4 kpc，造父变星为2.7 +/- 0.3 kpc。这证实了许多早期研究所提出的SMC深度很大。年轻人的取向与老恒星大不相同。我们发现天琴座RR型星的倾角为7° +/- 15°，位置角为83° +/- 21°，而造父变星的倾角为74° +/- 9°，位置角为66° +/- 15°。天琴座RR型星的分布相当均匀，而造父变星的分布则大致遵循天琴座的分布，它们的东北部比天琴座的西南部更靠近我们。SMC，LMC和银河系之间的相互作用可能是SMC年轻人口的倾斜，细长结构的原因。
Three dimensional maps of the Magellanic Clouds using RR~Lyrae stars and Cepheids - I. The Large Magellanic Cloud
光学引力透镜实验（OGLE-III）巡天的造父变星和天琴座RR型星的新数据使我们能够研究由这些变星追踪的大麦云（LMC）年轻（几千万年到几亿年）和年老（通常超过9 Gyr）恒星群的三维分布。我们估计的距离16949 RR天琴座恒星使用光度估计的金属丰度。此外，1849年造父变星的周期被用来确定它们的距离。通过使用来自这些恒星的固有颜色的个人红化估计得到的三维地图。由此产生的中位距离的RR天琴座恒星和造父变星似乎解决了长和短距离尺度的问题，为我们的样本。猎户座RR型恒星的距离中值为53.1 \pm 3.2 kpc，造父变星的距离中值为53.9 \pm 1.8 kpc，这两个距离指标与许多早期的研究相比非常吻合。个别红化的估计，使我们能够解决的距离差异经常观察到，而比较造父变星和RR天琴座恒星。对于这两个恒星星族，我们发现大麦哲伦星云的倾角为32° \pm 4°，平均位置角为115° \pm 15°。位置角随银河中心半径的增加而增加，表明有轻微的扭转。在OGLE III覆盖的LMC最里面的7度内，位置角的变化超过10度。造父变星的深度为1.7 \pm 0.2千秒差距。无论是在天琴座RR型恒星还是造父变星中，这条线都是密度过高的。在天琴座RR型恒星中，可以追踪到在盘主体前方有一个突出的超密度条，其视线深度约为5千秒差距。
Single star evolution does not allow extremely low-mass stars to cross the classical instability strip (IS) during the Hubble time. However, within binary evolution framework low-mass stars can appear inside the IS once the mass transfer (MT) is taken into account. Triggered by a discovery of low-mass 0.26 Msun RR Lyrae-like variable in a binary system, OGLE-BLG-RRLYR-02792, we investigate the occurrence of similar binary components in the IS, which set up a new class of low-mass pulsators. They are referred to as Binary Evolution Pulsators (BEPs) to underline the interaction between component…
Context. The multiplicity of classical Cepheids (CCs) and RR Lyrae stars (RRLs) is still imperfectly known, particularly for RRLs. Aims. In order to complement the close-in short orbital period systems presented in Paper I, our aim is to detect the wide, spatially resolved companions of the targets of our reference samples of Galactic CCs and RRLs. Methods. Angularly resolved common proper motion pairs were detected using a simple progressive selection algorithm to separate the most probable candidate companions from the unrelated field stars. Results. We found 27 resolved, high probability gr…
RR Lyrae Stars In The GCVS Observed By The Qatar Exoplanet Survey
我们使用卡塔尔系外行星巡天（QES）的光变曲线档案来研究变星总表（GCVS）中列出的天琴座RR型变星。在研究的588个变星中，我们将14个重新分类为食双星，一个是RS Canum Venaticorum型变星，一个是不规则变星，四个是经典造父变星，一个是II型造父变星，同时还改进了它们的周期。我们还报告了65个变量的新的RR Lyrics子类型分类，并改进了135个RR Lyrics变量的GCVS周期估计。有七个双模RR天琴座星的样本中，我们测量了他们的基本和第一泛音周期。最后，我们首次在38颗天琴座RR型恒星中探测到了Blazhko效应，并成功地测量了其中26颗恒星的Blazhko周期。
Messier 15 (NGC 7078) is an old and metal-poor post core-collapse globular cluster which hosts a rich population of variable stars. We report new optical ($gi$) and near-infrared (NIR, $JK_s$) multi-epoch observations for 129 RR Lyrae, 4 Population II Cepheids (3 BL Herculis, 1 W Virginis), and 1 anomalous Cepheid variable candidate in M15 obtained using the MegaCam and the WIRCam instruments on the 3.6-m Canada-France-Hawaii Telescope. Multi-band data are used to improve the periods and classification of variable stars, and determine accurate mean magnitudes and pulsational amplitudes from th…
Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, to date only one RRL has convincingly been demonstrated to be a binary, TU UMa, out of tens of thousands of known RRLs. Our aim is to detect the binary and multiple stars present in a sample of Milky Way CCs and RRLs. In the present article, we combine the Hipparcos and Gaia DR2 positions to determine the mean proper motion of the targets, and we search …
We present an overview of the Specific Objects Study (SOS) pipeline developed within the Coordination Unit 7 (CU7) of the Gaia Data Processing and Analysis Consortium (DPAC), the coordination unit charged with the processing and analysis of variable sources observed by Gaia, to validate and fully characterise Cepheids and RR Lyrae stars observed by the spacecraft. We describe how the SOS for Cepheids and RR Lyrae stars (SOS Cep&RRL) was specifically tailored to analyse Gaia's G-band photometric time-series with a South Ecliptic Pole (SEP) footprint, which covers an external region of the Large…
Stellar Pulsation and Evolution: a Combined Theoretical Renewal and Updated Models (SPECTRUM) -- I: Updating radiative opacities for pulsation models of Classical Cepheid and RR-Lyrae
本研究作为SPECTRUM项目首篇成果，更新Stellingwerf脉动代码的辐射不透明度表，发现该更新对经典造父变星与天琴座RR型变星的脉动性质及距离标尺定标影响极小，为构建自洽的恒星演化与脉动框架迈出重要一步。
The additional signals observed in the frequency spectra of the first-overtone RR Lyrae stars, that form a period ratio around 0.61 with the period of the first overtone, are a common phenomenon for RRc and RRd stars, as well as for first-overtone classical Cepheids. The recently proposed model explains these signals as harmonics of non-radial modes of degrees 8 or 9 in the case of RR Lyrae stars and 7, 8, or 9 in the case of classical Cepheids. We selected at least triple-mode RR Lyrae stars pulsating in radial and non-radial modes for asteroseismic modeling. We assume the identification of t…
Preliminary results for RR Lyrae stars and Classical Cepheids from the Vista Magellanic Cloud (VMC) Survey
Vista麦哲伦云（VMC，PI M.R. Cioni）调查正在收集由两个麦哲伦云（MC）和连接它们的“桥梁”形成的系统的$K_S$波段时间序列测光。这些数据被用来建立MC RR型天琴座恒星和经典造父变星的$K_S$波段光变曲线，并利用$K_S$波段周期光度（$PLK_S$）、周期-光度-颜色（$PLC$）和适用于这些类型变星的Wesenhiet关系确定整个系统的绝对距离和三维几何。作为调查潜力的一个例子，我们提出的结果，从VMC观测的两个领域分别集中在南极和30剑鱼座恒星形成区的大麦云。在这两个区域中，天琴座RR型星的VMC $K_S$波段光变曲线具有非常好的光度质量，单个数据点的典型误差在$\sim$ 0.02 ~ 0.05等之间。造父变星具有极好的光变曲线（典型误差为$\sim$ 0.01等）。这两种类型的变量的平均$K_S$幅度推导出的$PLK_S$关系，在一般良好的协议与文献数据的误差内，并显示比以前的研究更小的分散。
We present a comparison of the Gaia DR1 samples of pulsating variable stars - Cepheids and RR Lyrae type - with the OGLE Collection of Variable Stars aiming at the characterization of the Gaia mission performance in the stellar variability domain. Out of 575 Cepheids and 2322 RR Lyrae candidates from the Gaia DR1 samples located in the OGLE footprint in the sky, 559 Cepheids and 2302 RR Lyrae stars are genuine pulsators of these types. The number of misclassified stars is low indicating reliable performance of the Gaia data pipeline. The completeness of the Gaia DR1 samples of Cepheids and RR …
RR Lyrae Studies with Kepler
NASA的{ \it Kepler}任务提供的壮观数据不仅推动了围绕其他恒星运行的行星的发现，而且还打开了一扇了解恒星内部运作的窗户。对于天琴座RR型恒星的研究，开普勒带来了突破。到目前为止，在开普勒领域中已知的RR型天琴座恒星超过50颗。开普勒天文地震科学联合会（Kepler Asteroseismic Science Consortium，KASC）的天琴座/造父变星RR工作组对它们进行了研究。本文重点介绍了一些最有趣的结果RR天琴座星通过开普勒到目前为止。
The pulsating variable star population in DDO210
我们探测了孤立的本星系群矮星系DDO 210（宝瓶座）的脉动变星的内容，使用档案高级相机的调查/ $Hubble$ $Space$ $Telescope$成像在F475 W和F814 W通带。我们发现总共有32颗天琴座RR型星（24颗ab型，8颗c型）和75颗造父变星。计算出b型和c型天琴座RR型星的平均周期分别为$\langle$ P $_{\mathrm{ab}}\rangle = 0.609\pm0.011$和$\langle$ P $_{\mathrm{c}}\rangle = 0.359\pm0.025$日。基模天琴座RR型恒星的光变曲线特性给出了这个古老星群的平均金属丰度为$\langle$ [Fe/H] $\rangle$ = -1.63 $\pm$ 0.11 dex，这与最近的合成色星等图分析结果一致。我们发现这个星系是奥斯特霍夫中间，缺乏高振幅，短周期的ab型RR天琴座，与最近观察到的许多矮球状体和超微弱的矮星在本地集团的行为一致。我们发现距离模数$μ= 25.07\pm 0.12$确定的RR天琴座恒星，稍大，但同意最近的距离估计从红巨星分支尖端。我们还发现了一个相当大的人口造父变星在这个星系。我们提供的证据支持大多数，如果不是所有的这些恒星是短周期经典造父变星。假设所有这些恒星都是经典的造父变星，我们发现这些造父变星中的大多数都有3亿年的历史，最年轻的造父变星与…
A joint 1% calibration of the RR Lyrae & type-II Cepheid Leavitt laws yields homogeneous distances to 93 Galactic globular clusters
本研究通过联合校准RR星团和II型脉动变星的Leavitt定律，实现了93个银河球状星团的高精度均质距离测量。
Variable Stars in Large Magellanic Cloud Globular Clusters II: NGC 1786
这是研究大麦云球状星团中变星的系列论文中的第二篇。本系列的主要目标是研究在奥斯特霍夫中间系统中的RR型天琴座星与奥斯特霍夫I/II系统中的对应星的比较。在本文中，我们提出了我们的新的时间序列BV光度学研究的球状星团NGC 1786的结果。在我们的视野中总共识别出65颗变星。这些变星包括53颗天琴座RR型变星（27颗RRab，18颗RRc和8颗RRd），3颗经典造父变星，1颗II型造父变星，1颗反常造父变星，2颗食双星，3颗盾牌座Delta/凤凰座SX变星，以及2颗未确定类型的变星。这些变量的光度参数。我们目前的一些RR天琴座恒星的物理性质，来自傅立叶分析他们的光变曲线。我们讨论了Oosterhoff型的几个不同的指标，这些指标表明NGC 1786的Oosterhoff分类并不像大多数球状星团那样清晰。
The period of pulsation and the structure of the light curve for Cepheid and RR Lyrae variables depend on the fundamental parameters of the star: mass, radius, luminosity, and effective temperature. Here we train artificial neural networks on theoretical pulsation models to predict the fundamental parameters of these stars based on their period and light curve structure. We find significant improvements to estimates of these parameters made using light curve structure and period over estimates made using only the period. Given that the models are able to reproduce most observables, we find tha…
Stellar Variability and Distance Indicators in the Near-infrared in Nearby Galaxies. I. RR Lyrae and Anomalous Cepheids in Draco dwarf spheroidal
本文利用近红外多历元测光首次推导天龙座矮球状星系中天琴座RR型星和异常造父变星的周期-光度关系，并据此获得该星系迄今最精确的距离81.55 kpc。
We present a chemo-dynamical study of the Orphan stellar stream using a catalog of RR~Lyrae pulsating variable stars for which photometric, astrometric, and spectroscopic data are available. Employing low-resolution spectra from the Sloan Digital Sky Survey (SDSS), we determined line-of-sight velocities for individual exposures and derived the systemic velocities of the RR~Lyrae stars. In combination with the stars' spectroscopic metallicities and \textit{Gaia} EDR3 astrometry, we investigated the northern part of the Orphan stream. In our probabilistic approach, we found 20 single mode RR~Lyr…
We discuss the impact that Gaia, a European Space Agency (ESA) cornerstone mission that has been in scientific operations since July 2014, is expected to have on the definition of the cosmic distance ladder and the study of resolved stellar populations in and beyond the Milky Way, specifically focusing on results based on Cepheids and RR Lyrae stars. Gaia is observing about 1.7 billion sources, measuring their position, trigonometric parallax, proper motions and time-series photometry in 3 pass-bands down to a faint magnitude limit of G $\sim$21 mag. Among them are thousands of Cepheids and hu…
Gaia DR3: Specific processing and validation of all-sky RR Lyrae and Cepheid stars -- The Cepheid sample
本文介绍盖亚DR3中通过SOS Cep&RRL管线处理的全天15,006颗各类造父变星星表，包含多波段测光与表征，并发现474颗新造父变星。
A large extension of the Sextans dwarf spheroidal galaxy, 7 sq degrees, has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope in Cerro Tololo Inter-American Observatory, Chile. We report 7 Anomalous Cepheids, 199 RR Lyrae stars and 16 dwarf Cepheids in the field. This is only the fifth extra-galactic systems in which dwarf Cepheids have been systematically searched. Henceforth, the new stars increase the census of stars coming from different environments that can be used to asses the advantages and limitations of using dwarf Cepheids as standard candles in p…
We report the discovery of high velocity candidates among RR~Lyrae stars found in the Milky Way halo. We identified 9 RR~Lyrae stars with Galactocentric velocities exceeding the local escape velocity based on the assumed Galaxy potential. Based on close examination of their orbits', we ruled out their ejection location in the Milky Way disk and bulge. The spatial distribution revealed that seven out of 9 pulsators overlap with the position of the Sagittarius stellar stream. Two out of these seven RR~Lyrae stars can be tentatively linked to the Sagittarius dwarf spheroidal galaxy on the basis o…
Recent photometric observations of first-overtone classical Cepheids and RR Lyrae stars have led to the discovery of additional frequencies showing a characteristic period ratio of 0.60-0.65 with the main pulsation mode. In a promising model proposed by Dziembowski (2016), these signals are suggested to be due to the excitation of non-radial modes with degrees 7, 8 and 9 (Cepheids) or 8 and 9 (RR Lyrae). Such modes usually have low amplitudes in photometric data. Spectroscopic time series offer an unexplored and promising way forward. We simulated time series of synthetic line profiles for a r…
Space-based photometric measurements first revealed low-amplitude irregularities in the pulsations of Cepheid stars, but their origins and how commonly they occur remain uncertain. To investigate this phenomenon, we present MOST space telescope photometry of two Cepheids. V473 Lyrae is a second-overtone, strongly modulated Cepheid, while U Trianguli Australis is a Cepheid pulsating simultaneously in the fundamental mode and first overtone. The nearly continuous, high-precision photometry reveals alternations in the amplitudes of cycles in V473 Lyr, the first case of period doubling detected in…
We present measurements of the periods, amplitudes, and types of 74 RR Lyrae stars in the globular cluster M15 derived from Nickel 1 m telescope observations conducted at LickObservatory in 2019 and 2020. Of these RR Lyrae stars, two were previously reported but without a determination of the period. In addition, we identify five Type II Cepheid variable stars for which we report three novel period determinations, and a further 34 stars with uncertain classifications and periods. We discuss the development and subsequent application to our data of a new Python package, Period-determination and…
Double-mode radial-non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge
非径向模式激发在经典的双折射，无论是在造父变星和RR天琴座星。有力的证据来自第一泛音调制器，其中检测到特征周期比在0.60和0.65之间的附加较短周期模式。在第一泛音造父变星的情况下，在彼得森图（周期比与较长周期的图）中形成了三个独立的序列，其中有近200颗恒星。在第一泛音天琴座RR型星（RRc型星）的情况不太清楚。已知有十几颗这样的恒星，它们在彼得森图中形成一个没有任何明显结构的团块。有趣的是，所有的第一泛音RR天琴座星，精确的星载测光可显示额外的模式，这表明它的激发是常见的。受这些结果的启发，我们寻找非径向模式的OGLE-III测光的RRc恒星从银河系球。我们报告发现了147颗恒星，它们是一组新的双模、径向-非径向模式辐射子的成员。它们在彼得森图中形成了一个清晰而紧密的序列，周期比聚集在0.613左右，可能是周期比更高（0.631）的第二个序列。已知恒星的周期比的分散被解释为是由于人口效应。从空间观测的结果来看，这种仍然神秘的脉动形式在RRc恒星中一定很常见，而我们对OGLE数据的分析只是触及冰山一角。
Distance Scale Zero-Points from Galactic RR Lyrae Star Parallaxes
我们提出了7颗Pop II变星的新的绝对三角视差和自行：5颗RR Lyr变星; RZ Cep，XZ Cyg，SU Dra，RR Lyr，UV Oct;和2颗2型造父变星; VY Pyx和κ Pav。这些结果是用哈勃空间望远镜的白光干涉仪和精制导敏感器的天体测量数据得到的。我们发现绝对弛豫在毫秒弧：RZ Cep，2.12 \pm 0.16 mas; XZ Cyg，1.67 \pm 0.17 mas; SU Dra，1.42 \pm 0.16 mas; RR Lyr，3.77 \pm 0.13 mas; UV Oct，1.71 \pm 0.10 mas; VY Pyx，6.44 \pm 0.23 mas;和κ Pav，5.57 \pm 0.28 mas;平均σπ/π = 5.4%。有了这些振幅，我们计算的V和K带通星际消光和Lutz-Kelker-Hanson偏置校正的绝对幅度。使用这些RRL绝对量值，然后我们导出MV -[Fe/H]和MK -[Fe/H]-Log P关系的零点。简化的松弛技术证实了这些结果。利用我们的新结果确定了几个银河系球状星团的距离和年龄以及大麦哲伦星系的距离。后者接近于以前从经典造父变星中得到的未校正的金属丰度效应，表明任何这种效应都很小。我们还讨论了我们的两个2型造父变星得到的有点令人困惑的结果。
On the period distribution of cluster RR Lyrae stars to constrain their helium content: the case of omega Centauri
我们提出了一套新的非线性，时间依赖的对流流体动力学模型的RR天琴座恒星假设两个金属（Z=0.0005，Z=0.001）和三个氦丰度（Y=0.24，0.30，0.38）。对于每种化学成分，我们构建了一个网格的基本（FU）和第一泛音（FO）模型，涵盖了广泛的恒星质量和光度。为了限制氦含量对RR Lyonian性质的影响，我们采用了两个观测值-周期分布，光度振幅-这是独立的距离和红化。目前的预测证实，氦含量的脉动性能有一个边际效应。导致正则观测量和氦增强观测量之间差异的关键参数是光度。我们比较了目前的预测与样本的189 RR天琴座恒星在欧米茄Cen，我们发现，周期范围的He增强模型是系统地比观察到的更长。这些发现适用于金属贫和金属中间氦增强模型。为了进一步限制He增强结构对周期分布的影响，我们还计算了一系列合成HB模型，我们发现预测的周期分布，基于质量的高斯采样，与观测结果吻合得很好。这不仅适用于天琴座RR型恒星的最小基本周期（0.39对0.34天），也适用于II型造父变星的比例（2%对3%）。我们还计算了一系列的合成HB模型，假设混合HB人口，其中80%是由典型的HB结构，而20%是由氦增强（Y=0.30）HB结构。我们发现，这些模型预测的II型造父变星的比例几乎是观察到的两倍（5%对3%）。这表明ω Cen中的He增强结构的分数不能大于20%。
NGC 6441 is a bulge globular cluster with an unusual horizontal branch morphology and a rich population of RR Lyrae (RRL) and Type II Cepheid (T2C) variables that is unexpected for its relatively high metallicity. We present near-infrared (NIR, $JHK_s$) time-series observations of 42 RRL, 8 T2Cs, and 10 eclipsing binary candidate variables in NGC 6441. The multi-epoch observations were obtained using the FLAMINGOS-2 instrument on the 8-m Gemini South telescope. Multi-band data are used to investigate pulsation properties of RRL and T2C variables including their light curves, instability strip,…
The Swift/UVOT Stars Survey. II. RR Lyrae Stars in M 3 and M 15
本文介绍了雨燕伽马射线暴任务中紫外光学望远镜（UVOT）对天琴座RR型恒星进行近紫外（NUV）观测的第一批结果。众所周知，天琴座RR在远紫外和近紫外波段都有很大的振幅。我们利用UVOT独特的宽视场NUV成像能力，对银河系球状星团M3和M15中的变星进行了首次系统的NUV调查。我们确定了280颗变星，其中包括275颗天琴座RR型变星，两颗异常造父变星，一颗经典造父变星，一颗凤凰座SX型变星和一颗可能的长周期或不规则变星。其中只有两个是新发现。我们比较我们的结果与以前的调查，并发现在NUV的振幅显着较大的时期非常一致。首次绘制了球状星团的NUV Bailey图，给出了基模RRab和第一泛音RRc振子的常见轨迹。我们展示了NUV测光对RR型天琴座星的温度和表面重力的独特敏感性。最后，我们展示了NUV周期-金属丰度-光度关系的证据。未来的研究将进一步研究NUV脉动参数对金属丰度和Oosterhoff分类的依赖性。
Gaia DR3: Specific processing and validation of all-sky RR Lyrae and Cepheid stars -- The RR Lyrae sample
Gaia DR3发布经SOS流水线确认的270905颗全天RR天琴座恒星星表，包含脉动参数、金属丰度等丰富信息，较DR2规模近翻倍，为迄今最大最均匀的RRLs样本。
Method: In an accompanying paper (arXiv: 1705.00886) we determined luminosity and effective temperature for the 335 T2Cs and ACs in the LMC and SMC discovered in the OGLE-III survey, by constructing the spectral energy distribution (SED) and fitting this with model atmospheres and a dust radiative transfer model (in the case of dust excess). Building on these results we study the PL and PR relations. Using existing pulsation models for RR Lyrae and classical Cepheids we derive the period-luminosity-mass-temperature-metallicity relations, and then estimate the pulsation mass. Results: The PL re…
Double-Mode Radial Pulsations among RR Lyrae Stars
双模态天琴座RR型星是研究水平分支星性质的重要对象。特别是，两个周期加上光谱特性给出了一个质量估计，是独立的进化模型。在这里，我们提出了59个新的银河系双模RR天琴座星发现的线性调查数据的基本径向模式和第一泛退出（RRd星）。这些恒星可能有助于约束场水平分支恒星的质量-金属丰度关系。此外，还验证了EROS-II在大麦哲伦星云中发现的新的RRd星。我们给出了更新的Petersen图和基模周期的分布。还介绍了从LINEAR和LMC EROS-II巡天中选出的变星的评论，包括非常罕见的天体：第三个已知的模式转换RR Lyr和造父变星同时以三种径向模式脉动。
Photometry of Variable Stars from THU-NAOC Transient Survey I: The First 2 Years
本文报道了清华大学-中国天文台瞬变巡天（TNTS）在1300平方度天区的首次两年观测中对恒星光变的探测结果。总共探测到1237颗亮度为0.1等的变星（包括299颗新变星）< 18.0 mag and magnitude variation >，时间尺度从几小时到几百天不等。在这些观测中，我们初步鉴定了661颗天琴座RR星，431颗双星，72颗半规则变星，29颗米拉星，11颗慢不规则变星，11颗RS犬座星，7颗剑鱼座Gamma星，5颗长周期变星，3颗室女座W星，3颗盾牌座Delta星，2颗异常造父变星，1颗造父变星，根据它们的时间序列变率指数Js和它们的相位图，确定了1颗类新星。此外，我们还发现14颗天琴座RR型星表现出Blazhko效应，67颗接触食双星表现出O 'Connell效应。由于天琴座RR型变星的光变周期和振幅取决于它们的化学成分，它们的光度观测可以用来研究金属丰度沿垂直于银盘方向的分布。我们发现，RR型天琴座恒星的金属丰度在靠近银河系平面的区域表现出较大的分散性（例如，-3.0 < [Fe/H] < 0），但在较大的银河系纬度趋于收敛于[Fe/H]~ -1.7。这种变化可能与星系晕中的RRAB天琴座星来自不同金属丰度和垂直距离的球状星团，即OoI和OoII星群有关，有利于双晕模型。
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