Four ‘Peculiar’ RRd stars observed by <i>K2</i>

Nemec, J. M.; Moskalik, P.

doi:10.1093/mnras/stab1929

Cited by 6 publications

(3 citation statements)

References 83 publications

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“…The FNPEAKS code is open-source software with excellent performance. It produces results consistent with other approaches (e.g., Period04, SigSpec, AOV software, and Lomb-Scargle periodogram) (Pietrukowicz et al 2019;Nemec & Moskalik 2021;Podlewska-Gaca et al 2021;Wrona et al 2022b;Iwanek et al 2022). To confirm the correctness of the analytic procedure, we perform a TEO analysis on KIC 5034333 as an example and compare the results with previous works.…”

Section: Reliability Of the Analytic Resultssupporting

confidence: 59%

Detection of Tidally Excited Oscillations in Kepler Heartbeat Stars

Li,

Qian,

Zhu

et al. 2024

ApJ

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Heartbeat stars (HBSs) with tidally excited oscillations (TEOs) are ideal laboratories for studying the effect of equilibrium and dynamical tides. However, studies of TEOs in Kepler HBSs are rare due to the need for better modeling of the equilibrium tide in light curves. We revisit the HBSs in our previous work and study the TEOs in these HBSs based on the derived orbital parameters that could express the equilibrium tide. We also compile a set of analytic procedures to examine the harmonic and anharmonic TEOs in their Fourier spectra. The TEOs of 21 HBSs have been newly analyzed and presented. Twelve of these HBSs show prominent TEOs (signal-to-noise ratio of the harmonics S/N ≥ 10). The relation between the orbital eccentricities and the harmonic number of the TEOs shows a positive correlation. The relation between the orbital periods and the harmonic number also shows a positive correlation. Furthermore, the distribution of HBSs with TEOs in the Hertzsprung–Russell diagram shows that TEOs are more visible in hot stars with surface effective temperatures T ≳ 6500 K. These samples may also be valuable targets for future studies of the effect of tidal action in eccentric orbits.

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Section: Reliability Of the Analytic Resultssupporting

confidence: 59%

Detection of Tidally Excited Oscillations in Kepler Heartbeat Stars

Li,

Qian,

Zhu

et al. 2024

ApJ

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“…There are also anomalous and peculiar RRd stars. The anomalous or peculiar RRd stars are located above or below the sequence of classical RRd stars on the Petersen diagram (Nemec & Moskalik 2021). The dominant mode of the anomalous or peculiar RRd stars is the fundamental mode, while the dominant mode of classical RRd stars is the first-overtone mode.…”

Section: Introductionmentioning

confidence: 98%

Double-mode RR Lyrae star — robust distance and metallicity indicators

Wang,

Chen,

Zhang

et al. 2022

Proc. IAU

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RR Lyrae (RR Lyr) stars are a well-known and useful distance indicator for old stellar populations such as globular clusters and dwarf galaxies. Fundamental-mode RR Lyr (RRab) stars are commonly used to measure distances, and the accuracy of the determined distance is strongly constrained by metallicity. Here, we investigate the metallicity dependence in the period–luminosity (PL) relation of double-mode RR Lyr (RRd) stars. We find and establish a linear relation between metallicity and period or period ratio for RRd stars. This relation can predict the metallicity as accurately as the low-resolution spectra. Based on this relation, we establish a metallicity-independent PL relation for RRd stars. Combining the distance of the Large Magellanic Cloud and Gaia parallaxes, we calibrate the zero point of the derived PL relation to an error of 0.022 mag. Using RRd stars, we measure the distances of globular clusters and dwarf galaxies with an accuracy of 2-3% and 1-2%, respectively. In the future, RRd stars could anchor galaxy distances to an accuracy of 1.0% and become an independent distance ladder in the Local Group.

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“…1.2个星等。此外，RRc和RRab的周期存在0.4 d的分界线。综合利用这两项判据能使RRab和RRc 之间达到99%的分类正确率 [2] 。但如果考虑食双星和自转变星的混入，RRc的分类正确率通常在 90%左右。需要注意的是，各类天琴座RR型变星的变幅都会随着观测波长的增加逐渐下降，例如在红外W1波段(波长3.4 μm)，变幅只有光学V波段的0.1(RRab)~0.3倍(RRc) [6] 。这意味着利用红外设备(例如詹姆斯韦布望远镜)得到的光变曲线进行分类，正确率会显著下降。这就座RR型变星还存在非径向的脉动模式，它们的变幅通常为毫星等或更小，需要利用Kepler或TESS 望远镜探测 [7] 。在赫罗图或者星团、星系的颜色星等图上，RRab比RRc温度低约500 K，也就是 RRab的脉动不稳定带在RRc的红端(图1)。RRd同时存在两种周期，因此它存在于RRab和RRc 脉动不稳定带的重叠区域，即水平分支上RRab和RRc颜色分布区间的重叠部分。…”

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Distance measurement based on RR Lyrae variable stars

Chen,

Zhang,

Wang

et al. 2024

Chin. Sci. Bull.

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This paper summarizes the applications of RR Lyrae variable stars for distance measurements in the last 20 years. RR Lyrae stars are low-mass, metal-poor stars located in the overlap region of the pulsation instability strip and the horizontal branch. Due to the presence of radial pulsations, there are periodic brightness variations in RR Lyrae stars. RR Lyrae stars can be easily identified because of their sawtooth-shaped light curves. Based on the shape of the light curve, RR Lyrae stars can be mainly classified into fundamental mode (RRab), first-overtone mode (RRc) and double-mode (RRd) sub-types. With the development of large-scale time-domain telescopes, the current sample of RR Lyrae stars based on 1-meter-class telescopes is almost complete, with a number of about 300000 stars. RR Lyrae stars are good standard candles due to the tight relationship between luminosity and period and metallicity. The distance measurements based on RR Lyrae stars have also been optimized, gradually shifting from relying on visible metallicity-luminosity relations to infrared period-metallicity-luminosity relations. The zero points of the period-metallicity-luminosity relations for the RR Lyrae stars have been significantly optimized thanks to the improvement of the geometric distance of the Large Magellanic Cloud and the Gaia parallax. RRab stars and RRc stars were used to measure distances with an accuracy of about 5% for a single object and up to 2% for multiple objects. RRab stars have been the best distance tracer of old population for the last decades. On the basis of a large sample of RRab stars, the structure of the Galactic halo, bulge, and the Magellanic Clouds is refined, and the distances to globular clusters and dwarf galaxies are more accurately measured. In 2023, based on LAMOST and SDSS low resolution spectra, RRd stars were found to have period-luminosity relations that do not depend on metallicities. It is the only valuable object in standard candles that is independent of metallicities, and can break the bottleneck of the lack of metallicity in photometry-based distance measurements. RRd stars open the way to bulk measurements of high-precision distances to galaxies. Based on multiple RRd stars, the distance accuracy can be up to 1% which is better than distance accuracy based on RRab stars or tip of red giant branch stars. At the same time, RRd stars can also provide the metallicity of the objects to help optimize the accuracy of RRab star-based distances. With the future Chinese Space Station Telescope and other instruments, the number of RRd stars will increase to tens of thousands. RRd stars will be used to determine high-precision distances to hundreds of galaxies or dwarf galaxies with an error of about 1%, increasing that sample by a factor of 20, and will then be able to optimize the Hubble constant from multiple distance ladders.

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Four ‘Peculiar’ RRd stars observed by K2

Cited by 6 publications

References 83 publications

Detection of Tidally Excited Oscillations in Kepler Heartbeat Stars

Detection of Tidally Excited Oscillations in Kepler Heartbeat Stars

Double-mode RR Lyrae star — robust distance and metallicity indicators

Distance measurement based on RR Lyrae variable stars

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