Physical parameters of RR Lyrae stars in NGC 6171

Deras, Dan; Ferro, A. Arellano; Muneer, S.; Giridhar, Sunetra; Michel, R.

doi:10.1002/asna.201813489

Cited by 4 publications

(3 citation statements)

References 53 publications

(67 reference statements)

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“…For the nearby clusters (in particular M67) the Gaia parallaxes offer a useful constraint, while for the most distant clusters they provide very weak constraints. We also include the Harris (2010) tabulation of distances for globular clusters (with a 10% distance uncertainty for reference) and RR Lyrae standard candles where available (Benedict et al 2011; Deras et al 2018Deras et al , 2019Hernitschek et al 2019). Finally, for M67 we include distances measured from eclipsing binaries (Yakut et al 2009;Sandquist et al 2018) and from astroseismology of giants in the cluster (Stello et al 2016).…”

Section: Resultsmentioning

confidence: 99%

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

Cargile

Conroy

Johnson

et al. 2020

ApJ

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We present MINESweeper, a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry to model isochrones and spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition to stellar parameters such as T eff , g log , [Fe/H], [α/Fe], and radial velocity. MINESweeper employs a Bayesian framework and can easily incorporate a variety of priors, including Gaia parallaxes. Mock data are fit in order to demonstrate how the precision of derived parameters depends on evolutionary phase and signal-tonoise ratio. We then fit a selection of data in order to validate the model outputs. Fits to a variety of benchmark stars including Procyon, Arcturus, and the Sun result in derived stellar parameters that are in good agreement with the literature. We then fit combined spectra and photometry of stars in the open and globular clusters M92, M13, M3, M107, M71, and M67. Derived distances, [Fe/H], [α/Fe], and g log −T eff relations are in overall good agreement with literature values, although there are trends between metallicity and g log within clusters that point to systematic uncertainties at the ≈0.1 dex level. Finally, we fit a large sample of stars from the H3 Spectroscopic Survey in which high-quality Gaia parallaxes are also available. These stars are fit without the Gaia parallaxes so that the geometric parallaxes can serve as an independent test of the spectrophotometric distances. Comparison between the two reveals good agreement within their formal uncertainties after accounting for the Gaia zero-point uncertainties.

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Section: Resultsmentioning

confidence: 99%

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

Cargile

Conroy

Johnson

et al. 2020

ApJ

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“…For M67, we also compare the average distance measured from eclipsing binaries (Yakut et al 2009;Sandquist et al 2018) and from astroseismology of giants in the cluster (Stello et al 2016). For the globular clusters, we include distances from cluster RR Lyrae standard candles (Benedict et al 2011;Deras et al 2018;Hernitschek et al 2019;Deras et al 2019), and for M107 we also include a distance measurement based on the absolute magnitude of the cluster's horizontal giant branch (Harris 2010).…”

Section: Star Clustersmentioning

confidence: 99%

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

Cargile,

Conroy,

Johnson

et al. 2019

Preprint

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We present MINESweeper, a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry to model isochrones and spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition to stellar parameters such as T eff , log g, [Fe/H], [α/Fe], and radial velocity. MINESweeper employs a Bayesian framework and can easily incorporate a variety of priors, including Gaia parallaxes. Mock data are fit in order to demonstrate how the precision of derived parameters depends on evolutionary phase and SNR. We then fit a selection of data in order to validate the model outputs. Fits to the benchmark stars Procyon, Arcturus, and the Sun result in derived stellar parameters that are in excellent agreement with the literature, except for the surface gravity of Arcturus, where our value (1.35) is notably lower than the literature (1.66). We then fit combined spectra and photometry of stars in the open and globular clusters M92, M13, M3, M107, M71, and M67. Derived distances, [Fe/H], [α/Fe], and log g−T eff relations are in overall good agreement with literature values, although there are trends between metallicity and log g within clusters that point to systematic uncertainties at the ≈ 0.1 dex level. Finally, we fit a large sample of stars from the H3 Spectroscopic Survey in which high quality Gaia parallaxes are also available. These stars are fit without the Gaia parallaxes so that the geometric parallaxes can serve as an independent test of the spectrophotometric distances. Comparison between the two reveals excellent agreement within their formal uncertainties after accounting for the Gaia zero point uncertainties.

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“…NGC 6362 is now the third OoI cluster where we find the clean mode segregation, limited by the red edge of the first overtone instability strip. The other examples are NGC 6229 (Arellano Ferro et al ) and NGC 6171 (Deras et al , in preparation). It has been discussed by Yepez et al () that the mode segregation versus the mingled mode distribution in the intermode or “either‐or” region may be a consequence of the mass loss rates involved during the He flashes and, hence, the resulting mass distribution on the ZAHB, which in turn controls the mode population of the intermode region (Caputo et al ).…”

Section: The Horizontal Branch Of Ngc 6362mentioning

confidence: 99%

Metallicity and distance of NGC 6362 from its RR Lyrae and SX Phoenicis stars

et al. 2018

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New time-series VI CCD photometry of the globular cluster NGC 6362 is studied with the aim of estimating the reddening, mean metallicity, and distance of the cluster from its population of RR Lyrae stars. The Fourier decomposition of carefully selected single-mode RR Lyrae light curves, and the use of well-established semiempirical calibrations and revised zero points, lead to the values of [Fe/H] UVES −1.066 ± 0.126 and −1.08 ± 0.16 and distances of 7.93 ± 0.32 and 8.02 ± 0.15 kpc from the RRab and RRc stars, respectively. The distribution of RR Lyrae stars in the horizontal branch shows a neat segregation of pulsating modes about the red edge of the first overtone instability strip, which is not necessarily expected in an OoI-type cluster like NGC 6362. Four RRab stars are found to be likely advanced in their evolution toward the AGB. One new foreground SX Phe star, some 4 kpc in front of the cluster and projected onto the field of our images, is reported. We comment on the heavy light contamination, by a very close neighbouring star, of the peculiar double-mode V37 variable, recently postulated as a non-typical RRc variable. KEYWORDS globular clusters: individual (NGC 6362) -horizontal branch -RR Lyrae starsblue stragglers 1

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Physical parameters of RR Lyrae stars in NGC 6171

Cited by 4 publications

References 53 publications

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era

Metallicity and distance of NGC 6362 from its RR Lyrae and SX Phoenicis stars

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