English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We gathered more than 1130 high-resolution optical spectra for more than 250Galactic classical Cepheids. The spectra were collected with different opticalspectrographs: UVES at VLT, HARPS at 3.6m, FEROS at 2.2m MPG/ESO, and STELLA.To improve the effective temperature estimates, we present more than 150 newline depth ratio (LDR) calibrations that together with similar calibrationsalready available in the literature allowed us to cover a broad range inwavelength (between 5348 and 8427 angstrom) and in effective temperatures(between 3500 and 7700 K). This means the unique opportunity to cover both thehottest and coolest phases along the Cepheid pulsation cycle and to limit theintrinsic error on individual measurements at the level of ~100 K. Thanks tothe high signal-to-noise ratio of individual spectra we identified and measuredhundreds of neutral and ionized lines of heavy elements, and in turn, have theopportunity to trace the variation of both surface gravity and microturbulentvelocity along the pulsation cycle. The accuracy of the physical parameters andthe number of Fe I (more than one hundred) and Fe II (more than ten) linesmeasured allowed us to estimate mean iron abundances with a precision betterthan 0.1 dex. Here we focus on 14 calibrating Cepheids for which the currentspectra cover either the entire or a significant portion of the pulsationcycle. The current estimates of the variation of the physical parameters alongthe pulsation cycle and of the iron abundances agree quite well with similarestimates available in the literature. Independent homogeneous estimates ofboth physical parameters and metal abundances based on different approachesthat can constrain possible systematics are highly encouraged.

On a new and homogeneous metallicity scale for Galactic classical Cepheids - I. Physical parameters