High-precision distance measurements with classical pulsating stars

Bhardwaj, Anupam

doi:10.1007/s12036-020-09640-z

Cited by 42 publications

(29 citation statements)

References 279 publications

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“…Typical uncertainties in the zero points of the P/L relations of RR Lyrae stars are thought to be of order 0.05 mag (Bhardwaj 2020) and other methods like CMD fitting have similar uncertainties. In addition, the reddening of many clusters presents an additional challenge for the determination of accurate distances since it can be variable even across small, arcminute size fields Pallanca et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data

Baumgardt,

Vasiliev

2021

Preprint

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We have derived accurate distances to Galactic globular clusters by combining data from the Gaia Early Data Release 3 (EDR3) with distances based on Hubble Space telescope (HST ) data and literature based distances. We determine distances either directly from the Gaia EDR3 parallaxes, or kinematically by combining line-of-sight velocity dispersion profiles with Gaia EDR3 and HST based proper motion velocity dispersion profiles. We furthermore calculate cluster distances from fitting nearby subdwarfs, whose absolute luminosities we determine from their Gaia EDR3 parallaxes, to globular cluster main-sequences. We finally use HST based stellar number counts to determine distances. We find good agreement in the average distances derived from the different methods down to a level of about 2%. Combining all available data, we are able to derive distances to 162 Galactic globular clusters, with the distances to about 20 nearby globular clusters determined with an accuracy of 1% or better. We finally discuss the implications of our distances for the value of the local Hubble constant.

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Section: Introductionmentioning

confidence: 99%

Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data

Baumgardt,

Vasiliev

2021

Preprint

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“…Theoretically predicted boundaries of the fundamental red edge and the first-overtone blue edge of the IS are based on the empirical relations provided by Marconi et al [33]. Theoretically predicted magnitudes were converted to apparent magnitudes using the distance to the GC in the respective studies [24,44,48,80]. As expected, RRc are located towards the blue (hot) edge of the IS, while the RRab are towards the red (cool) edge of the IS.…”

Section: Color-magnitude Diagramsmentioning

confidence: 99%

“…NIR observations of RRL in the earliest studies on PLRs were limited to a few epochs or sparsely sampled light curves (e.g., [110][111][112]). With the advent of modern infrared detectors, several empirical investigations have been carried out on infrared PLRs for RRL stars in GCs ( [24,44,48,52,80,113], and references therein).…”

Section: Multiband Period-luminosity Relationsmentioning

confidence: 99%

“…It is beyond the scope of this article to provide a comprehensive overview of these variables in GCs, and therefore, it will focus on a comparative study of optical and infrared pulsation properties of population II variables. We refer readers to several excellent reviews on RRL and T2C variables available in the literature: [15,[17][18][19][20][21][22][23][24]. This article is organized as follows: the evolutionary and pulsational scenario for RRL and T2Cs is discussed in Section 2.…”

Section: Introductionmentioning

confidence: 99%

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RR Lyrae and Type II Cepheid Variables in Globular Clusters: Optical and Infrared Properties

Bhardwaj

2022

Universe

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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, including the light curves, color–magnitude and period–amplitude diagrams, and period–luminosity relations in globular clusters at optical and infrared wavelengths are presented. The RR Lyrae visual magnitude–metallicity relation and the multiband period–luminosity–metallicity relations in globular clusters covering a wide metallicity range are also discussed in detail for their application to the RR Lyrae-based distance scale.

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“…However, these phenomena were not found in all types of RR Lyrae. RR Lyrae stars can be classified by their pulsations as fundamental mode (RRab), first overtone (RRc), or multi-mode (RRd) RR Lyrae according to the number of oscillation modes (Soszyński et al 2016;Beaton et al 2018;Bhardwaj 2020). As for RRab stars, three moderate-to-weak hydrogen emission lines, named "three apparitions", appear sequentially in the spectra during a pulsation cycle (Preston 2011).…”

Section: Introductionmentioning

confidence: 99%

Possible evidence of hydrogen emission in the first-overtone and multi-mode RR Lyrae variables

Duan,

Chen,

Deng

et al. 2020

Preprint

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The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of hydrogen emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer emissions. The emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with hydrogen emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.

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High-precision distance measurements with classical pulsating stars

Cited by 42 publications

References 279 publications

Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data

Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data

RR Lyrae and Type II Cepheid Variables in Globular Clusters: Optical and Infrared Properties

Possible evidence of hydrogen emission in the first-overtone and multi-mode RR Lyrae variables

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