Evidence for Galactic disc RR Lyrae stars in the solar neighbourhood

Prudil, Z.; Dékány, I.; Grebel, Eva K.; Kunder, Andrea

doi:10.1093/mnras/staa046

Cited by 35 publications

(43 citation statements)

References 117 publications

(199 reference statements)

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“…The steady decrease in α-enhancement is more clear in Ti and Ca for which the variation is of the order of ∼0.6 dex, but it is also present in Mg. Very metal-poor (Fe/H]≤-2.2) RRLs are strongly enhanced in α-elements ([α/Fe]∼0.4 to 0.5), while those approaching solar iron abundance are depleted in α-elements ([α/Fe]∼-0.2 to -0.3, see also Prudil et al 2020). iii) Similar dispersion for Ca and Ti -Both Ca and Ti display trends in tight agreement and can be considered the same within uncertainties.…”

Section: The Individual Speciesmentioning

confidence: 96%

On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances*

Crestani

Braga

Fabrizio

et al. 2021

ApJ

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Section: The Individual Speciesmentioning

confidence: 96%

On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances*

Crestani

Braga

Fabrizio

et al. 2021

ApJ

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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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“…This makes them ideal for studying the very early stages of the formation of the Milky Way, and for the identification of accretion events in the Galaxy (Iorio & Belokurov 2019). Recently, it has been noticed that many RR Lyrae stars appear to be on disc-like orbits (Marsakov et al 2019;Iorio & Belokurov 2020;Prudil et al 2020) indicating that the traditional viewpoint is incomplete and alternative channels for RR Lyrae star production, possibly through binary evolution, are possible. A variable star catalogue then allows the construction of samples of different stellar populations with precise distances and low contamination, tracing different evolutionary stages in the Galaxy.…”

Section: Introductionmentioning

confidence: 99%

Variable star classification across the Galactic bulge and disc with the VISTA Variables in the Vía Láctea survey

Molnar

Sanders

Smith

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present VIVACE, the VIrac VAriable Classification Ensemble, a catalogue of variable stars extracted from an automated classification pipeline for the Vista Variables in the Vía Láctea (VVV) infrared survey of the Galactic bar/bulge and southern disc. Our procedure utilises a two-stage hierarchical classifier to first isolate likely variable sources using simple variability summary statistics and training sets of non-variable sources from the Gaia early third data release, and then classify candidate variables using more detailed light curve statistics and training labels primarily from OGLE and VSX. The methodology is applied to point-spread-function photometry for ∼490 million light curves from the VIRAC v2 astrometric and photometric catalogue resulting in a catalogue of ∼1.4 million likely variable stars, of which ∼39, 000 are high-confidence (classification probability >0.9) RR Lyrae ab stars, ∼8000 RR Lyrae c/d stars, ∼187, 000 detached/semi-detached eclipsing binaries, ∼18, 000 contact eclipsing binaries, ∼1400 classical Cepheid variables and ∼2200 Type II Cepheid variables. Comparison with OGLE-4 suggests a completeness of around 90 per cent for RRab and ≲ 60 per cent for RRc/d, and a misclassification rate for known RR Lyrae stars of around 1 per cent for the high confidence sample. We close with two science demonstrations of our new VIVACE catalogue: first, a brief investigation of the spatial and kinematic properties of the RR Lyrae stars within the disc/bulge, demonstrating the spatial elongation of bar-bulge RR Lyrae stars is in the same sense as the more metal-rich red giant population whilst having a slower rotation rate of ∼40 km s−1kpc−1; and secondly, an investigation of the Gaia EDR3 parallax zeropoint using contact eclipsing binaries across the Galactic disc plane and bulge.

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Evidence for Galactic disc RR Lyrae stars in the solar neighbourhood

Cited by 35 publications

References 117 publications

On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances*

On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances*

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

Variable star classification across the Galactic bulge and disc with the VISTA Variables in the Vía Láctea survey

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