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Context. Classical Cepheids (DCEPs) are crucial for calibrating the extragalactic distance ladder, ultimately enabling the determination of the Hubble constant through the period-luminosity (PL) and period-Wesenheit (PW) relations that they exhibit. Hence, it is vital to understand how the PL and PW relations depend on metallicity. This is the purpose of the C-MetaLL survey, within which this work is situated. The DCEPs are also very important tracers of the young populations placed along the Galactic disc. Aims. We aim to enlarge the sample of DCEPs with accurate abundances from high-resolution spectroscopy. In particular, our goal is to extend the range of measured metallicities towards the metal-poor regime to better cover the parameter space. To this end, we observed objects in a wide range of Galactocentric radii, allowing us to study in detail the abundance gradients present in the Galactic disc. Methods. We present the results of the analysis of 331 spectra obtained for 180 individual DCEPs with a variety of high-resolution spectrographs. For each target, we derived accurate atmospheric parameters, radial velocities, and abundances for up to 29 different species. The iron abundances range between 0.5 and −1 dex with a rather homogeneous distribution in metallicity. Results. The sample presented in this paper was complemented with that already published in the context of the C-MetaLL survey, resulting in a total of 292 pulsators whose spectra have been analysed in a homogeneous way. These data were used to study the abundance gradients of the Galactic disc in a range of Galactocentric radii (RGC) spanning the range of 5–20 kpc. Conclusions. For most of the elements, we have found a clear negative gradient, with a slope of −0.064 ± 0.003 dex kpc−1 for [Fe/H] case. Through a qualitative fit with the Galactic spiral arms, we show how our farthest targets (RGC > 10 kpc) trace both the Outer and Outer Scutum-Centaurus arms. The homogeneity of the sample will be of pivotal importance for the study of the metallicity dependence of the DCEP PL relations. [ABSTRACT FROM AUTHOR]

Context. Type II Cepheids (T2Cs) are the less frequently used counterparts of classical or type I Cepheids (CCs) which provide the primary calibration of the distance ladder for measuring the Hubble constant in the local Universe. In the era of the "Hubble tension", T2C variables together with the RR Lyrae stars and the tip of the red giant branch (TRGB) can potentially provide non-CC-dependent calibration of the cosmic distance ladder. Aims. Our goal is to provide an absolute calibration of the period–luminosity, period–luminosity–colour, and period–Wesenheit relations (PL, PLC, and PW, respectively) of T2Cs in the Large Magellanic Cloud (LMC), which traditionally serves as a crucial first anchor of the extragalactic distance ladder. Methods. We exploited time-series photometry in the near-infrared (NIR) Y,  J, and Ks bands for a sample of approximately 320 T2Cs in the Magellanic Clouds (MCs). These observations were acquired during 2009–2018 in the context of the VISTA survey of the Magellanic Clouds system (VMC), an ESO public survey. We supplemented the NIR photometry from the VMC survey with well-sampled optical light curves and accurate pulsation periods from the Optical Gravitational Lensing Experiment (OGLE) IV survey and the Gaia mission. We used the best-quality NIR light curves to generate custom templates for modelling sparsely sampled light curves in YJKs bands. Results. The best-fitting YJKs template light curves were used to derive accurate and precise intensity-averaged mean magnitudes and pulsation amplitudes of 277 and 62 T2Cs in the LMC and SMC, respectively. We used optical and NIR mean magnitudes for different T2C subclasses (BLHer, WVir, and RVTau) to derive PL/PLC/PW relations in multiple bands, which were calibrated with the geometric distance to the LMC as derived from eclipsing binaries and with the Gaia parallaxes. We used our new empirical calibrations of PL and PW relations to obtain distances to 22 T2C-host Galactic globular clusters, which were found to be systematically smaller by ∼0.1 mag and 0.03−0.06 mag than in the literature when the zero points are calibrated with the distance of the LMC or Gaia parallaxes, respectively. Better agreement is found between our distances and those based on RR Lyrae stars in globular clusters, providing strong support for using these population II stars together with the TRGB for future distance scale studies. [ABSTRACT FROM AUTHOR]

Context. Anomalous Cepheids (ACEPs) are intermediate-mass metal-poor pulsators that are mostly discovered in dwarf galaxies of the Local Group. However, recent Galactic surveys, including the Gaia Data Release 3, found a few hundred ACEPs in the Milky Way. Their origin is only poorly understood. Aims. We aim to investigate the origin and evolution of Galactic ACEPs by studying the chemical composition of their atmospheres for the first time. Methods. We used UVES at the Very Large Telescope to obtain high-resolution spectra for a sample of nine ACEPs belonging to the Galactic halo. We derived the abundances of 12 elements, C, Na, Mg, Si, Ca, Sc, Ti, Cr, Fe, Ni, Y, and Ba. We complemented these data with literature abundances from high-resolution spectroscopy for an additional three ACEPs that were previously incorrectly classified as type II Cepheids. This increased the sample to a total of 12 stars. Results. All the investigated ACEPs have an iron abundance [Fe/H] < −1.5 dex, as expected from theoretical predictions for these pulsators. The abundance ratios of the different elements to iron show that the chemical composition of ACEPs is generally consistent with that of the Galactic halo field stars, with the exception of sodium, which is found to be overabundant in 9 out of the 11 ACEPs where it was measured. This is very similar to the situation for second-generation stars in Galactic globular clusters. The same comparison with dwarf and ultra-faint satellites of the Milky Way reveals more differences than similarities. It is therefore unlikely that the bulk of Galactic ACEPs originated in a galaxy like this that subsequently dissolved into the Galactic halo. The principal finding of this work is the unexpected overabundance of sodium in ACEPs. We explored several hypotheses to explain this feature, finding that the most promising scenario is the evolution of low-mass stars in a binary system with either mass transfer or merging. Detailed modelling is needed to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

Classical Cepheids (DCEPs) are the first fundamental step in the calibration of the cosmological distance ladder. Furthermore, they represent powerful tracers in the context of Galactic studies. We have collected high-resolution spectroscopy with UVES@VLT for a sample of 65 DCEPs. The majority of them are the faintest DCEPs ever observed in the Milky Way. For each target, we derived accurate atmospheric parameters, radial velocities, and abundances for 24 different species. The resulting iron abundances range between +0.3 and −1.1 dex with the bulk of stars at [Fe/H] ∼ −0.5 dex. Our sample includes the most metal-poor DCEPs observed so far with high-resolution spectroscopy. We complement our sample with literature data obtaining a complete sample of 637 DCEPs and use Gaia Early Data Release 3 (EDR3) photometry to determine the distance of the DCEPs from the period–Wesenheit–Metallicity relation. Our more external data trace the Outer arm [at Galactocentric radius (RGC) ∼ 16–18 kpc] which appears significantly warped. We investigate the metallicity gradient of the Galactic disc using this large sample, finding a slope of −0.060 ± 0.002 dex kpc−1, in very good agreement with previous results based both on DCEPs and open clusters. We also report a possible break in the gradient at RGC = 9.25 kpc with slopes of −0.063 ± 0.007 and −0.079 ± 0.003 dex kpc−1 for the inner and outer sample, respectively. The two slopes differ by more than 1σ. A more homogeneous and extended DCEPs sample is needed to further test the plausibility of such a break. [ABSTRACT FROM AUTHOR]

Erratum: Cepheid metallicity in the Leavitt law (C-metall) survey - I. HARPS-N@TNG spectroscopy of 47 classical Cepheids and 1 BL Her variables Keywords: errata; addenda; stars: abundances; stars: distances; stars: fundamental parameters; stars: variables: Cepheids; distance scale EN errata addenda stars: abundances stars: distances stars: fundamental parameters stars: variables: Cepheids distance scale 2887 2890 4 09/29/22 20221030 NES 221030 This is an erratum to the paper Cepheid metallicity in the Leavitt law (C-metall) survey - I. HARPS-N@TNG spectroscopy of 47 classical Cepheids and 1 BL Her variables, published in MNRAS, 2021, 508, 4047-4071. Errata, stars: abundances, stars: distances, stars: fundamental parameters, distance scale, addenda, stars: variables: Cepheids. [Extracted from the article]

Classical Cepheids (DCEPs) are the most important primary indicators of the extragalactic distance scale. Establishing the dependence on metallicity of their period–luminosity and period–Wesenheit (PLZ / PWZ) relations has deep consequences on the calibration of secondary distance indicators that lead to the final estimate of the Hubble constant (H 0). We collected high-resolution spectroscopy for 47 DCEPs plus 1 BL Her variables with HARPS-N@TNG and derived accurate atmospheric parameters, radial velocities, and metal abundances. We measured spectral lines for 29 species and characterized their chemical abundances, finding very good agreement with previous results. We re-determined the ephemerides for the program stars and measured their intensity-averaged magnitudes in the V, I, J, H, K s bands. We complemented our sample with literature data and used the Gaia Early Data Release 3 (EDR3) to investigate the PLZ / PWZ relations for Galactic DCEPs in a variety of filter combinations. We find that the solution without any metallicity term is ruled out at more than the 5σ level. Our best estimate for the metallicity dependence of the intercept of the PLK s, PWJK s, PWVK s, and PWHVI relations with three parameters is −0.456 ± 0.099, −0.465 ± 0.071, −0.459 ± 0.107, and −0.366 ± 0.089 mag dex−1, respectively. These values are significantly larger than the recent literature. The present data are still inconclusive to establish whether or not also the slope of the relevant relationships depends on metallicity. Applying a correction to the standard zero-point offset of the Gaia parallaxes has the same effect of reducing by ∼22 per cent the size of the metallicity dependence on the intercept of the PLZ / PWZ relations. [ABSTRACT FROM AUTHOR]

Context. Classical Cepheids (DCEPs) are the most important primary indicators for the extragalactic distance scale. Establishing the dependence on metallicity of their period–luminosity and period–Wesenheit (PL and PW) relations has deep consequences for the estimate of the Hubble constant (H0). Aims. We investigate the dependence on metal abundance ([Fe/H]) of the PL and PW relations for Galactic DCEPs. Methods. We combined proprietary and literature photometric and spectroscopic data, gathering a total sample of 413 Galactic DCEPs (372 fundamental mode, DCEP_F, and 41 first-overtone, DCEP_1O) and constructed new metallicity-dependent PL and PW relations in the near-infrared adopting the astrometry-based luminosity. Results. We find indications that the slopes of the PL(KS) and PW(J, KS) relations for Galactic DCEPs might depend on metallicity on the basis of the comparison with the Large Magellanic Cloud relationships. Therefore we used a generalized form of the PL and PW relations to simultaneously take the metallicity dependence of the slope and intercept of these relations into account. Conclusions. We calculated PL and PW relations that for the first time explicitly include a metallicity dependence of the slope and intercept terms. The quality of the available data is insufficient, however, and we cannot yet present conclusive results, but they are relevant from a methodological point of view. The new relations are linked to the geometric measurement of the distance to the Large Magellanic Cloud and allowed us to estimate a Gaia DR2 parallax zero-point offset Δϖ = 0.0615 ± 0.004 mas from the dataset of DCEPs used in this work. [ABSTRACT FROM AUTHOR]