Observational calibration of the projection factor of Cepheids

Gallenne, A.; Kervella, P.; Mérand, A.; Pietrzyński, G.; Gieren, W.; Nardetto, N.; Trahin, Boris

doi:10.1051/0004-6361/201731589

Cited by 34 publications

(48 citation statements)

References 63 publications

(86 reference statements)

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“…Furthermore, we perform a comparison with literature relations of our PR (Figure 9). We confirm a general good agreement with Molinaro et al (2012) and Gallenne et al (2017) PR relations. However we better reproduce Molinaro et al (2012) relation at shorter periods whereas the opposite occurs with Gallenne et al (2017) relation.…”

Section: The Period-radius and The Period-mass-radius Relationssupporting

confidence: 92%

“…However we better reproduce Molinaro et al (2012) relation at shorter periods whereas the opposite occurs with Gallenne et al (2017) relation. We finally note that the PR relations obtained by Molinaro et al (2012) and Gallenne et al (2017) depend on the assumed projection-factor (p-factor) value 5 , while those derived by the models do not depend on this parameter (Ragosta et al 2019) . Therefore a comparison between these two independent derivations allows us to put constraints on the value of the p-factor (e.g.…”

Section: The Period-radius and The Period-mass-radius Relationssupporting

confidence: 52%

“…The p-factor is the parameter which connects the observed radial velocity to the model radial velocity (see e.g Gallenne et al (2017)). …”

mentioning

confidence: 99%

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An Extended Theoretical Scenario for Classical Cepheids. I. Modeling Galactic Cepheids in the Gaia Photometric System

Somma

Marconi

Molinaro

et al. 2020

ApJS

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We present a new extended and detailed set of models for Classical Cepheid pulsators at solar chemical composition (Z = 0.02, Y = 0.28) based on a well tested nonlinear hydrodynamical approach. In order to model the possible dependence on crucial assumptions such as the Mass-Luminosity relation of central Helium burning intermediate-mass stars or the efficiency of superadiabatic convection, the model set was computed by varying not only the pulsation mode and the stellar mass but also the Mass-Luminosity relation and the mixing length parameter that is used to close the system of nonlinear hydrodynamical and convective equations. The dependence of the predicted boundaries of the instability strip as well as of both light and radial velocity curves on the assumed Mass-Luminosity and the efficiency of superadiabatic convection is discussed. Nonlinear Period-Mass-Luminosity-Temperature,

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Section: The Period-radius and The Period-mass-radius Relationssupporting

confidence: 92%

Section: The Period-radius and The Period-mass-radius Relationssupporting

confidence: 52%

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An Extended Theoretical Scenario for Classical Cepheids. I. Modeling Galactic Cepheids in the Gaia Photometric System

Somma

Marconi

Molinaro

et al. 2020

ApJS

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“…There are systematic differences between these two models of order 15%. Compared to the adopted reddenings from the literature the Green et al (2019) (2016), theory, Z = 0.014, ω ini = 0.5, average 2nd and 3rd crossing 0.676 ± 0.006 1.173 ± 0.008 -- Petroni et al (2003), theory, solar metallicity 0.684 ± 0.007 1.135 ± 0.002 -0.020 Gallenne et al (2017), p = 1.33 − 0.08 log P 0.665 ± 0.012 1.136 ± 0.014 162 0.055 Groenewegen (2013), p = 1.50 − 0.24 log P 0.737 1.074 162 -Groenewegen (2013), p = 1.33 0.75 ± 0.03 1.10 ± 0.03 26 0.036 Molinaro et al (2011), p = 1.27 0.767 ± 0.009 1.091 ± 0.011 8 - Kervella et al (2004a) 0.747 ± 0.028 1.071 ± 0.025 13 0.009 Turner & Burke (2002), p = 1.31 0.680 ± 0.017 1.146 ± 0.007 44 0.045 Gieren et al (1999), p = 1.39 − 0.03 log P 0.750 ± 0.024 1.075 ± 0.007 28 0.036 Gieren et al (1998), p = 1.39 − 0.03 log P 0.751 ± 0.026 1.070 ± 0.008 40 0.051 Laney & Stobie (1995), p = 1.36 Fig. 9.…”

Section: Discussion and Summarymentioning

confidence: 96%

Analysing the spectral energy distributions of Galactic classical Cepheids

Groenewegen

2020

A&A

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Spectral energy distributions (SEDs) were constructed for a sample of 477 classical cepheids (CCs); including stars that have been classified in the literature as such but are probably not. The SEDs were fitted with a dust radiative transfer code. Four stars showed a large mid-or far-infrared excess and the fitting then included a dust component. These comprise the well-known case of RS Pup, and three stars that are (likely) Type-II cepheids (T2Cs), AU Peg, QQ Per, and FQ Lac. The infrared (IR) excess in FQ Lac is reported for the first time in this work. The remainder of the sample was fitted with a stellar photosphere to derive the best-fitting luminosity and effective temperature. Distance and reddening were taken from the literature. The stars were plotted in a Hertzsprung-Russell diagram (HRD) and compared to evolutionary tracks for cepheids and theoretical instability strips. For the large majority of stars, the position in the HRD is consistent with the instability strip for a CC or T2C. About 5% of the stars are outliers in the sense that they are much hotter or cooler than expected. A comparison to effective temperatures derived from spectroscopy suggests in some cases that the photometrically derived temperature is not correct and that this is likely linked to an incorrectly adopted reddening. Two three-dimensional reddening models have been used to derive alternative estimates of the reddening for the sample. There are significant systematic differences between the two estimates with a non-negligible scatter. In this work the presence of a small near-infrared (NIR) excess, as has been proposed in the literature for a few well-known cepheids, is investigated. Firstly, this was done by using a sample of about a dozen stars for which a mid-infrared spectrum is available. This data is particularly constraining as the shape of the observed spectrum should match that of the photosphere and any dust spectrum, both dust continuum and any spectral features of, for example, silicates or aluminium oxide. This comparison provides constraints on the dust composition, in agreement with a previous work in the literature. Secondly, the SEDs of all stars were fitted with a dust model to see if a statistically significant better fit could be obtained. The results were compared to recent work. Eight new candidates for exhibiting a NIR excess are proposed, solely based on the photometric SEDs. Obtaining mid-infrared spectra would be needed to confirm this excess. Finally, period-bolometric luminosity and period-radius relations are presented for samples of over 370 fundamental-mode CCs.

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“…Pilecki et al (2018)), have produced a milder dependence (e.g. Gallenne et al (2017)), or even values consistent with a zero period dependence of the p-factor . However, these studies show a large scatter among the projection factors of individual Cepheids, hinting at large systematic uncertainties on the individual determinations , and/or a possible intrinsic dispersion of the p factors of Cepheids of similar periods.…”

Section: Discussionmentioning

confidence: 99%

The effect of metallicity on Cepheid period-luminosity relations from a Baade-Wesselink analysis of Cepheids in the Milky Way and Magellanic Clouds

Gieren

Storm

Konorski

et al. 2018

A&A

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Context. The extragalactic distance scale builds on the Cepheid period-luminosity (PL) relation. Decades of work have not yet convincingly established the sensitivity of the PL relation to metallicity. This currently prevents a determination of the Hubble constant accurate to 1% from the classical Cepheid-SN Ia method. Aims. In this paper, we want to carry out a strictly differential comparison of the absolute PL relations obeyed by classical Cepheids in the Milky Way (MW), LMC and SMC galaxies. Taking advantage of the substantial metallicity difference among the Cepheid populations in these three galaxies, we want to establish a possible systematic trend of the PL relation absolute zero point as a function of metallicity, and determine the size of such an effect in optical and near-infrared photometric bands. Methods. We are using the IRSB Baade-Wesselink type method as calibrated by Storm et al. to determine individual distances to the Cepheids in our samples in MW, LMC and SMC. For our analysis, we use a greatly enhanced sample of Cepheids in the SMC (31 stars) as compared to the small sample (5 stars) available in our previous work. We use the distances to determine absolute Cepheid PL relations in optical and near-infrared bands in each of the three galaxies. Results. Our distance analysis of 31 SMC Cepheids with periods from 4-69 days yields tight PL relations in all studied bands, with slopes consistent with the corresponding LMC and MW relations. Adopting the very accurately determined LMC slopes for the optical and near-infrared bands, we determine the zero point offsets between the corresponding absolute PL relations in the 3 galaxies. We find that in all bands the metal-poor SMC Cepheids are intrinsically fainter than their more metal-rich counterparts in the LMC and MW. In the K band the metallicity effect is −0.23 ± 0.06 mag/dex while in the V, (V − I) Wesenheit index it is slightly stronger, −0.34±0.06 mag/dex. We find some evidence that the PL relation zero point-metallicity relation might be nonlinear, becoming steeper for lower metallicities. Conclusions. Using sizeable Cepheid samples in the MW, LMC and SMC with very accurate photometric and radial velocity data we establish the metallicity sensitivity of the Cepheid PL relations in the optical and near-infrared regimes. We find a significant effect in all bands in the sense that the more metal-poor SMC Cepheids are intrinsically fainter than their LMC and Galactic counterparts. We find suggestive evidence that the metallicity sensitivity of the PL relation might be nonlinear, being small in the range between solar and LMC Cepheid metallicity, and becoming steeper towards the lower-metallicity regime.

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Observational calibration of the projection factor of Cepheids

Cited by 34 publications

References 63 publications

An Extended Theoretical Scenario for Classical Cepheids. I. Modeling Galactic Cepheids in the Gaia Photometric System

An Extended Theoretical Scenario for Classical Cepheids. I. Modeling Galactic Cepheids in the Gaia Photometric System

Analysing the spectral energy distributions of Galactic classical Cepheids

The effect of metallicity on Cepheid period-luminosity relations from a Baade-Wesselink analysis of Cepheids in the Milky Way and Magellanic Clouds

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