X-ray Observations of the Peculiar Cepheid V473 Lyr Identify A Low-Mass Companion
Nancy Remage Evans, Ignazio Pillitteri, Laszlo Molnar, Laszlo Szabados, Emese Plachy, Robert Szabo, Scott Engle, Ed Guinan, Scott Wolk, H. Moritz Guenther, Hild… 展开作者
Nancy Remage Evans, Ignazio Pillitteri, Laszlo Molnar, Laszlo Szabados, Emese Plachy, Robert Szabo, Scott Engle, Ed Guinan, Scott Wolk, H. Moritz Guenther, Hilding Neilson, Massimo Marengo, Lynn D. Matthews, Sofia Moschou, Jeremy J. Drake, Vinay Kashyap, Pierre Kervella, Tamas Tordai, Peter Somogyi, Gilbert Burki
V473 Lyr is a classical Cepheid which is unique in having substantial amplitude variations with a period of approximately 3.3 years, thought to be similar to the Blazhko variations in RR Lyrae stars. We obtained an {\it XMM-Newton} observation of this star to followup a previous detection in X-rays. Rather than the X-ray burst and rapid decline near maximum radius seen in $δ$ Cephei itself, the X-ray flux in V473 Lyr remained constant for a third of the pulsation cycle covered by the observation. Thus the X-rays are most probably not produced by the changes around the pulsation cycle. The X-ray spectrum is soft (kT = 0.6 keV), with
X-ray properties which are consistent with a young low mass companion. Previously there was no evidence of a companion in radial velocities or in {\it Gaia} and {\it Hipparcos} proper motions. While this rules out companions which are very close or very distant, a binary companion at a separation between 30 and 300 AU is possible. This is an example of an X-ray observation revealing evidence of a low mass companion, which is important in completing the mass ratio statistics of binary Cepheids. Furthermore, the detection of a young X-ray bright companion is a further indication that the Cepheid (primary) is a Population I star, even though its pulsation behavior differs from other classical Cepheids.
Gaia's Cepheids and RR Lyrae Stars and Luminosity Calibrations Based on Tycho-Gaia Astrometric Solution
盖亚数据发布1包含超过700颗银河系造父变星和RR型天琴座恒星的星表,作为第谷-盖亚天体测量解决方案(TGAS)的一部分进行计算。我们利用TGAS光度计,结合文献($V, I, J, {K_\mathrm{s}}, W_1$)光度学和光谱学,标定了经典造父变星和II型造父变星的周期-光度和周期-韦森关系的零点,以及近红外周期-光度、周期-光度-金属丰度和光学光度-金属丰度关系。在这方面的贡献,我们简要地总结了通过拟合这些基本关系,采用不同的技术,无论是在视差或距离(绝对星等)空间。
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 …
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…
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
Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?
When a Period Is Not a Full Stop: Light Curve Structure Reveals Fundamental Parameters of Cepheid and RR Lyrae Stars
Aarhus University(奥胡斯大学);State University of New York(纽约州立大学);INAF-Osservatorio Astronomico di Capodimonte(意大利国家天体物理研究所-卡波迪蒙特天文台);Peking University(北京大学)
The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy
智利托洛洛山美洲天文台的布兰科望远镜用暗能量照相机对六分仪矮球状星系的一个7平方度的大扩展区进行了变星观测。我们报告了7颗异常造父变星、199颗天琴座RR星和16颗矮造父变星。这只是第五个星系外的矮造父变星已被系统地搜索。尽管如此,新的恒星增加了来自不同环境的恒星的普查,可以用来评估使用矮造父变星作为标准烛光的优势和局限性,因为这些恒星的金属丰度不一定是已知的。在六分仪座发现的矮造父变星的平均周期为0.066天,平均$g$振幅为0.87磁等。它们位于水平分支的下方,跨度为0.8等,介于$21.9 < g < 22.7$之间。与船底座等其他星系相比,六分仪座中的矮造父变星数量较少,而船底座星系拥有大量的中年人口。另一方面,天琴座RR型恒星与矮造父变星的数量和比例与玉夫座非常相似,玉夫座是一个像六分仪座一样被古老的恒星星族所控制的星系。在六分仪中发现的造父矮星遵循一个很好的周期-光度关系,在$g$波段的均方根=0.05等,这是通过锚定到由天琴座RR型恒星给出的距离模量而建立的。虽然六分仪座中的大多数变星都位于星系的中心,但我们在星系的外围发现了2颗天琴座RR星和1颗异常造父变星,它们可能是潮汐外恒星,表明该星系可能正在经历潮汐破坏。这些可能的潮外变星与六分仪座有着相同的自行,正如最近的盖亚测量所看到的。
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 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…
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,…