Local RR Lyrae stars: native and alien

Zinn, R.; Chen, X; Layden, Andrew C.; Casetti-Dinescu, Dana I.

doi:10.1093/mnras/stz3580

Cited by 21 publications

(22 citation statements)

References 107 publications

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“…Note that we could not perform this step for the RAVE metallicities because we found only one match between the RAVE and the HR+∆S RRLs, therefore the RAVE metallicities were not converted. We also note that, the fits for the Zinn et al (2020), Dambis et al (2013), Duffau et al (2014) and Sesar et al (2013) samples are close to the bisector, meaning that their metallicities aretaking account of the uncertainties -already in a scale very similar to our own. Additionally, we found that the metallicity scales of Liu et al (2020) and SEGUE-SSPP are different to ours.…”

Section: The Rrl Spectroscopic Catalogsupporting

confidence: 73%

On the Use of Field RR Lyrae as Galactic Probes. I. The Oosterhoff Dichotomy Based on Fundamental Variables*

Fabrizio

Bono

Braga

et al. 2019

ApJ

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We collected a large data set of field RR Lyrae stars (RRLs) by using catalogues already available in the literature and Gaia DR2. We estimated the iron abundances for a sub-sample of 2,382 fundamental RRLs (∆S method: Ca II K, Hβ, Hγ and Hδ lines) for which are publicly available medium-resolution SDSS-SEGUE spectra. We also included similar estimates available in the literature ending up with the largest and most homogeneous spectroscopic data set ever collected for RRLs (2,903). The metallicity scale was validated by using iron abundances based on high resolution spectra for a fundamental field RRL (V Ind), for which we collected X-shooter spectra covering the entire pulsation cycle. The peak ([Fe/H]=-1.59±0.01) and the standard deviation (σ=0.43 dex) of the metallicity distribution agree quite well with similar estimates available in the literature. The current measurements disclose a well defined metal-rich tail approaching Solar iron abundance. The spectroscopic sample plotted in the Bailey diagram (period vs luminosity amplitude) shows a steady variation when moving from the metal-poor ([Fe/H]=-3.0/-2.5) to the metal-rich ([Fe/H]=-0.5/0.0) regime. The smooth transition in the peak of the period distribution as a function of the metallicity strongly indicates that the longstanding problem of the Oosterhoff dichotomy among Galactic globulars is the consequence of the lack of metal-intermediate clusters hosting RRLs. We also found that the luminosity amplitude, in contrast Corresponding author: Michele Fabrizio michele.fabrizio@ssdc.asi.it * Partially based on observations collected under ESO programmes 297.D-5047 (PI. G. Bono) and 083.B-0281 (PI. D. Romano). arXiv:1908.02064v2 [astro-ph.SR] 7 Aug 2019 M. Fabrizio et al.with period, does not show a solid correlation with metallicity. This suggests that period-amplitudemetallicity relations should be cautiously treated.

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Section: The Rrl Spectroscopic Catalogsupporting

confidence: 73%

On the Use of Field RR Lyrae as Galactic Probes. I. The Oosterhoff Dichotomy Based on Fundamental Variables*

Fabrizio

Bono

Braga

et al. 2019

ApJ

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“…The mean azimuthal velocity of the thin disc indicates that the motion of the Sun is around 232.5 km s −1 , which is consistent with the recent value derived from classical cepheids (Ablimit et al 2020). The faster azimuthal velocity and more metal-rich features of the thin disc compared to other components are consistent with previous studies (e.g., Preston 1959;Taam et al 1976;Layden 1995;Mateu & Vivas 2018;Marsakov et al 2019;Prudil et al 2020;Zinn et al 2020;Iorio & Belokurov 2021). There are relatively more thick disc stars in this work, and they do not rotate as fast as the thin disc stars.…”

Section: Properties Of Thin Disc Thick Disc and Halosupporting

confidence: 92%

“…The structure of the Milky Way thick disc have been characterized by RRLs as tracers (e.g., Layden 1995;Amrose & Mckay 2001). Zinn et al (2020) and Prudil et al (2020) combined RRL with available spectroscopy and Gaia DR2 astrometry to confirm the existence of metal-rich RRL stars with the orbital properties typical of the Galactic thin disc.…”

Section: Introductionmentioning

confidence: 99%

The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History

Ablimit,

Zhao,

Teklimakan

et al. 2021

Preprint

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In order to study the Milky Way, RR Lyrae (RRL) variable stars identified by Gaia, ASAS-SN and ZTF sky survey projects have been analyzed as tracers in this work. Photometric and spectroscopic information of 3417 RRLs including proper motions, radial velocity and metallcity are obtained from observational data of Gaia, LAMOST, GALAH, APOGEE and RAVE. Precise distances of RRLs with typical uncertainties less than 3% are derived by using a recent comprehensive period-luminosity-metallicity relation. Our results from kinematical and chemical analysis provide important clues for the assembly history of the Milky Way, especially for the Gaia-Sausage ancient merger. The kinematical and chemical trends found in this work are consistent with that of recent simulations which indicated that the Gaia-Sausage merger is the dual origin of the Galactic thick disc and halo. As recent similar works have found, the halo RRLs sample in this work contains a subset of radially biased orbits besides a more isotropic component. This higher orbital anisotropy component amounts to β 0.8, and it contributes between 42% and 83% of the halo RRLs at 4 < R(kpc) < 20.

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“…Hansen et al 2016) but they are also known to exist in the disc of the Galaxy (e.g. Layden 1995a; Liu et al 2013;Zinn et al 2020;Prudil et al 2020) and their formation mechanisms have long been source of puzzling (e.g. Taam et al 1976;Layden 1995b;Marsakov et al 2019).…”

Section: Formation Channels For Metal-rich Rr Lyrae Starsmentioning

confidence: 99%

The age of the Milky Way inner stellar spheroid from RR Lyrae population synthesis

Savino

Koch

Prudil

et al. 2020

A&A

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The central kiloparsecs of the Milky Way are known to host an old, spheroidal stellar population, whose spatial and kinematical properties set it apart from the boxy-peanut structure that constitutes most of the central stellar mass. The nature of this spheroidal population, whether it is a small classical bulge, the innermost stellar halo, or a population of disk stars with large initial velocity dispersion, remains unclear. This structure is also a promising candidate to play host to some of the oldest stars in the Galaxy. Here we address the topic of the inner stellar spheroid age, using spectroscopic and photometric metallicities for a sample of 935 RR Lyrae stars that are constituents of this component. By means of stellar population synthesis, we derive an age-metallicity relation for RR Lyrae populations. We infer, for the RR Lyrae stars in the bulge spheroid, an extremely ancient age of 13.41 ± 0.54 Gyr and conclude they were among the first stars to form in what is now the Milky Way galaxy. Our age estimate for the central spheroid shows a remarkable agreement with the age profile that has been inferred for the Milky Way stellar halo, suggesting a connection between the two structures. However, we find mild evidence for a transition in the halo properties at rGC ∼ 5 kpc. We also investigate formation scenarios for metal-rich RR Lyrae stars, such as binarity and helium variations, and consider whether they can provide alternative explanations for the properties of our sample. We conclude that within our framework, the only viable alternative is to have younger, slightly helium-rich, RR Lyrae stars. This is a hypothesis that would open intriguing questions for the formation of the inner stellar spheroid.

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Local RR Lyrae stars: native and alien

Cited by 21 publications

References 107 publications

On the Use of Field RR Lyrae as Galactic Probes. I. The Oosterhoff Dichotomy Based on Fundamental Variables*

On the Use of Field RR Lyrae as Galactic Probes. I. The Oosterhoff Dichotomy Based on Fundamental Variables*

The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History

The age of the Milky Way inner stellar spheroid from RR Lyrae population synthesis

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