Atmospheric parameters of Cepheids from flux ratios with ATHOS

Context. The effective temperature is a key parameter governing the properties of a star. For stellar chemistry, it has the strongest impact on the accuracy of the abundances derived. Since Cepheids are pulsating stars, determining their effective temperature is more complicated than in the case of nonvariable stars. Aims. We want to provide a new temperature scale for classical Cepheids, with a high precision and full control of the systematics. Methods. Using a data-driven machine learning technique employing observed spectra, and in taking great care to accurately phase single-epoch observations, we tied flux ratios to (label) temperatures derived using the infrared surface brightness method. Results. We identified 143 flux ratios, which allow us to determine the effective temperature with a precision of a few Kelvin and an accuracy better than 150 K, which is in line with the most accurate temperature measures available to date. The method does not require a normalization of the input spectra and provides homogeneous temperatures for low- and high-resolution spectra, even at the lowest signal-to-noise ratios. Due to the lack of a dataset with a sufficient sample size for Small Magellanic Cloud Cepheids, the temperature scale does not extend to Cepheids with [Fe/H] < −0.6 dex. However, it nevertheless provides an exquisite, homogeneous means of characterizing Galactic and Large Magellanic Cloud Cepheids. Conclusions. The temperature scale will be extremely useful in the context of spectroscopic surveys for Milky Way archaeology with the WEAVE and 4MOST spectrographs. It paves the way for highly accurate and precise metallicity estimates, which will allow us to assess the possible metallicity dependence of Cepheids’ period-luminosity relations and, in turn, to improve our measurement of the Hubble constant H0.

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Period–luminosity–metallicity relation of classical Cepheids

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038714 ◽

2020 ◽

Vol 642 ◽

pp. A230

Author(s):

V. Ripepi ◽

G. Catanzaro ◽

R. Molinaro ◽

M. Marconi ◽

G. Clementini ◽

...

Keyword(s):

Near Infrared ◽

Data Gathering ◽

Hubble Constant ◽

Zero Point ◽

Total Sample ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Point Of View ◽

Classical Cepheids ◽

Metal Abundance

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.

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Candidates for non-pulsating stars located in the Cepheid instability strip in the Large Magellanic Cloud based on Strömgren photometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2112 ◽

2019 ◽

Vol 489 (3) ◽

pp. 3285-3293 ◽

Cited By ~ 1

Author(s):

Weronika Narloch ◽

G Pietrzyński ◽

Z Kołaczkowski ◽

R Smolec ◽

M Górski ◽

...

Keyword(s):

Gravitational Lensing ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Light Curves ◽

Instability Strip ◽

Classical Cepheid ◽

Pulsating Stars ◽

Giant Stars ◽

Classical Cepheids ◽

Astrophysical Research

ABSTRACT We present candidates for non-pulsating stars lying in the classical Cepheid instability strip based on the Optical Gravitational Lensing Experiment (OGLE) photometric maps combined with Strömgren photometry obtained with the 4.1-m Southern Astrophysical Research (SOAR) telescope, and Gaia Data Release 2 data in four fields in the Large Magellanic Cloud. We selected 19 candidates in total. After analysis of their light curves from OGLE surveys we found that all these stars appear to be photometrically stable at the level of a few mmag. Our results show that non-pulsating stars might constitute to about $21\!-\!30\, {\rm per\, cent}$ of the whole sample of giant stars located in the classical instability strip. Furthermore, we identified potential candidates for classical Cepheids with hot companions based on their Strömgren colours.

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A new and homogeneous metallicity scale for Galactic classical Cepheids

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833087 ◽

2018 ◽

Vol 616 ◽

pp. A82 ◽

Cited By ~ 3

Author(s):

B. Proxauf ◽

R. da Silva ◽

V. V. Kovtyukh ◽

G. Bono ◽

L. Inno ◽

...

Keyword(s):

Effective Temperature ◽

Signal To Noise Ratio ◽

High Signal ◽

Physical Parameters ◽

Classical Cepheids ◽

Microturbulent Velocity ◽

Metal Abundances ◽

Pulsation Cycle ◽

Intrinsic Error ◽

Better Than

We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with the optical spectrographs UVES at VLT, HARPS at 3.6 m, FEROS at 2.2 m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (5348 ≤ λ ≤ 8427 Å) and in effective temperature (3500 ≤ Teff ≤ 7700 K). This gives us the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100 K. As a consequence of the high signal-to-noise ratio of individual spectra, we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of Fe I (more than one hundred) and Fe II (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1 dex. We focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree very well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.

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THE PANCHROMATIC VIEW OF THE MAGELLANIC CLOUDS FROM CLASSICAL CEPHEIDS. I. DISTANCE, REDDENING, AND GEOMETRY OF THE LARGE MAGELLANIC CLOUD DISK

The Astrophysical Journal ◽

10.3847/0004-637x/832/2/176 ◽

2016 ◽

Vol 832 (2) ◽

pp. 176 ◽

Cited By ~ 42

Author(s):

L. Inno ◽

G. Bono ◽

N. Matsunaga ◽

G. Fiorentino ◽

M. Marconi ◽

...

Keyword(s):

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Magellanic Clouds ◽

Classical Cepheids

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Erratum: Candidates for non-pulsating stars located in the Cepheid instability strip in the Large Magellanic Cloud based on Strömgren photometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3291 ◽

2019 ◽

Vol 491 (2) ◽

pp. 2770-2770

Author(s):

Weronika Narloch ◽

G Pietrzyński ◽

Z Kołaczkowski ◽

R Smolec ◽

M Górski ◽

...

Keyword(s):

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Instability Strip ◽

Pulsating Stars

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ULTRA-LOW AMPLITUDE VARIABLES IN THE LARGE MAGELLANIC CLOUD—CLASSICAL CEPHEIDS, POP. II CEPHEIDS, RV TAU STARS, AND BINARY VARIABLES

The Astrophysical Journal ◽

10.1088/0004-637x/698/1/944 ◽

2009 ◽

Vol 698 (1) ◽

pp. 944-955 ◽

Cited By ~ 7

Author(s):

J. Robert Buchler ◽

Peter R. Wood ◽

Igor Soszyński

Keyword(s):

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Binary Variables ◽

Classical Cepheids ◽

Rv Tau Stars ◽

Low Amplitude

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A Review of the Distance and Structure of the Large Magellanic Cloud

Highlights of Astronomy ◽

10.1017/s1539299600016166 ◽

2005 ◽

Vol 13 ◽

pp. 448-449

Author(s):

David R. Alves

Keyword(s):

Excellent Agreement ◽

Hubble Space Telescope ◽

Total Error ◽

Hubble Constant ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Wilkinson Microwave Anisotropy Probe ◽

Distance Modulus ◽

Standard Distance ◽

Considerable Support

The debate about the distance to the Large Magellanic Cloud (LMC) has an epic history full of controversial and dramatic claims (i.e., see review by Walker 2003), and yet in recent years a standard distance modulus has emerged due primarily to the completion of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant (Preedman et al. 2001). The adopted standard distance modulus,µ0 = 18.5±0.1 mag, yields H0 = 71±10 km s−1 Mpc−1 (total error) in excellent agreement with that derived from the Wilkinson Microwave Anisotropy Probe: H0 72±5 km s−1 Mpc−1 (Spergel et al. 2003), which lends considerable support to its accuracy.

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Eclipsing Binaries in the Magellanic Clouds

Highlights of Astronomy ◽

10.1017/s153929960001618x ◽

2005 ◽

Vol 13 ◽

pp. 451-451

Author(s):

Andrzej Udalski

Keyword(s):

Gravitational Lensing ◽

Direct Determination ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Eclipsing Binaries ◽

Physical Parameters ◽

Second Phase ◽

Internet Archive ◽

Pulsating Stars ◽

Eclipsing Stars

We present results of a search for eclipsing binaries in the Magellanic Cloud fields covering central parts of these galaxies. The data were collected during the second phase of the Optical Gravitational Lensing Experiment survey (OGLE-II) in 1997-2000. In total, about 1500 and 3000 eclipsing stars were found in the Small and Large Magellanic Cloud, respectively (Udalski et al. 1998, Wyrzykowski et al. 2003). The photometric data of all objects are available to the astronomical community from the OGLE Internet archive (http://sirius.astrouw.edu.pl/~ogle/). OGLE-II data contain a full variety of classical eclipsing objects of all types: Algol EA-type, β-Lyr EB-type and W UMA EW-type stars. Large samples of stars allow to study in detail statistical properties of eclipsing objects. OGLE data also contain many very unusual eclipsing stars. Examples include eclipsing variable B-type stars (Mennickent et al. 2003), many spotted stars or eclipsing stars with a Cepheid as a component (Udalski et al. 1999). Recently three objects from the LMC revealing simultaneously RR Lyr and eclipsing binary type variability were discovered (Soszyński et al 2003). If the follow-up observations confirm that both components are physically bound and not optical blends these stars will provide a unique opportunity of direct determination of physical parameters of RR Lyr pulsating stars.

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