Extended envelopes around Galactic Cepheids

Gallenne, A.; Mérand, A.; Kervella, P.; Chesneau, O.; Breitfelder, J.; Gieren, W.

doi:10.1051/0004-6361/201322257

Cited by 32 publications

(54 citation statements)

References 41 publications

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“…It is particularly effective to use B, V observations to constrain the interstellar reddening, while infrared wavelengths give a stronger leverage for detecting circumstellar envelopes (see i.e Gallenne et al 2014Gallenne et al , 2013Kervella et al 2013;Gallenne et al 2011, for Galactic Cepheids) …”

Section: Data Samplementioning

confidence: 99%

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Observational calibration of the projection factor of Cepheids

Gallenne

Kervella

Mérand

et al. 2017

A&A

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Context. The Baade-Wesselink (BW) method, which combines linear and angular diameter variations, is the most common method to determine the distances to pulsating stars. However, the projection factor, p-factor, used to convert radial velocities into pulsation velocities, is still poorly calibrated. This parameter is critical on the use of this technique, and often leads to 5-10 % uncertainties on the derived distances. Aims. We focus on empirically measuring the p-factor of a homogeneous sample of 29 LMC and 10 SMC Cepheids for which an accurate average distances were estimated from eclipsing binary systems. Methods. We used the SPIPS algorithm, which is an implementation of the BW technique. Unlike other conventional methods, SPIPS combines all observables, i.e. radial velocities, multi-band photometry and interferometry into a consistent physical modelling to estimate the parameters of the stars. The large number and their redundancy insure its robustness and improves the statistical precision. Results. We successfully estimated the p-factor of several Magellanic Cloud Cepheids. Combined with our previous Galactic results, we find the following P − p relation: −0.08 ±0.04 (log P − 1.18) + 1.24 ±0.02 . We find no evidence of a metallicity dependent p-factor. We also derive a new calibration of the period-radius relation, log R = 0.684 ±0.007 (log P − 0.517) + 1.489 ±0.002 , with an intrinsic dispersion of 0.020. We detect an infrared excess for all stars at 3.6µm and 4.5µm, which might be the signature of circumstellar dust. We measure a mean offset of ∆m 3.6 = 0.057 ± 0.006 mag and ∆m 4.5 = 0.065 ± 0.008 mag. Conclusions. We provide a new P − p relation based on a multi-wavelength fit that can be used for the distance scale calibration from the BW method. The dispersion is due to the LMC and SMC width we took into account because individual Cepheids distances are unknown. The new P − R relation has a small intrinsic dispersion: 4.5 % in radius. This precision will allow us to accurately apply the BW method to nearby galaxies. Finally, the infrared excesses we detect again raise the issue of using mid-IR wavelengths to derive period-luminosity relation and to calibrate the Hubble constant. These IR excesses might be the signature of circumstellar dust, and are never taken into account when applying the BW method at those wavelengths. Our measured offsets may give an average bias of ∼ 2.8 % on the distances derived through mid-IR P − L relations.

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Section: Data Samplementioning

confidence: 99%

“…We know that some Galactic Cepheids have some IR emission which can bias the photometric estimates (see e.g. Gallenne et al 2013Gallenne et al , 2011Gallenne et al , 2010Barmby et al 2011). The SPIPS code allows fitting the IR excess, either using a simple offset for each wavelength or an analytical formula.…”

Section: Colour Excess and Circumstellar Envelopementioning

confidence: 99%

Observational calibration of the projection factor of Cepheids

Gallenne

Kervella

Mérand

et al. 2017

A&A

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“…Again, this value is for a given star and results from the various data-reduction techniques (e.g., bisector, cross-correlation) used to extract the radial velocity from spectra (Nardetto et al 2009). Another potential source of bias is the presence of circumstellar envelopes, which have been discovered and studied in the infrared by Kervella et al (2006), Mérand et al (2006Mérand et al ( , 2007, Kervella et al (2009), and Gallenne et al (2011, 2012, 2013. In the context of the parallax of pulsation, these envelopes affect the infrared apparent brightness of the star from the K-band (2 µm) and longward of this.…”

Section: Introductionmentioning

confidence: 99%

Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS)

Mérand

Kervella

Breitfelder

et al. 2015

A&A

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Context. The parallax of pulsation, and its implementations such as the Baade-Wesselink method and the infrared surface brightness technique, is an elegant method to determine distances of pulsating stars in a quasi-geometrical way. However, these classical implementations in general only use a subset of the available observational data. Aims. Freedman & Madore (2010, ApJ, 719, 335) suggested a more physical approach in the implementation of the parallax of pulsation in order to treat all available data. We present a global and model-based parallax-of-pulsation method that enables including any type of observational data in a consistent model fit, the SpectroPhoto-Interferometric modeling of Pulsating Stars (SPIPS). Methods. We implemented a simple model consisting of a pulsating sphere with a varying effective temperature and a combination of atmospheric model grids to globally fit radial velocities, spectroscopic data, and interferometric angular diameters. We also parametrized (and adjusted) the reddening and the contribution of the circumstellar envelopes in the near-infrared photometric and interferometric measurements. Results. We show the successful application of the method to two stars: δ Cep and η Aql. The agreement of all data fitted by a single model confirms the validity of the method. Derived parameters are compatible with publish values, but with a higher level of confidence. Conclusions. The SPIPS algorithm combines all the available observables (radial velocimetry, interferometry, and photometry) to estimate the physical parameters of the star (ratio distance/p-factor, T eff , presence of infrared excess, color excess, etc). The statistical precision is improved (compared to other methods) thanks to the large number of data taken into account, the accuracy is improved by using consistent physical modeling and the reliability of the derived parameters is strengthened thanks to the redundancy in the data.

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“…On the other hand, if we take as an upper limit to the age of the nebula the time that TMon has spent on the instability strip (∼70,000 yr; Bono et al 2000), this would translate to~´- M M 6 10 6 yr −1 . The first of these two estimates is two orders of magnitude higher than the mass-loss rate estimated by Gallenne et al (2013) based on the modeling of extended mid-IR emission » ´- M M 5.6 0.6 10 7 [˙( ) yr −1 , after scaling to our adopted distance]. However, given that the observations of Gallenne et al sample material within only  R 10 20 -, the mass-loss rate derived by those authors reflects only very recent or ongoing mass loss.…”

Section: Implications Of Mass Loss On the Evolutionary History Of Tmonmentioning

confidence: 73%

“…Extended IR emission was also detected with Spitzer around several other Cepheids by Barmby et al (2011), including three stars with extended emission seen in multiple IR bands and four other stars with evidence for extended emission in at least one band. In addition, on scales closer to the star, near-and mid-IR interferometry have revealed what appear to be warm, dusty circumstellar envelopes on scales ranging from a few stellar radii Mérand et al 2006;Gallenne et al 2013) to several hundred astronomical units (Kervella et al 2009). …”

Section: Introductionmentioning

confidence: 99%

A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS

Matthews

Marengo

Evans

2016

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We present the results of a search for H I 21 cm line emission from the circumstellar environments of four Galactic Cepheids (RS Pup, X Cyg, ζ Gem, and T Mon) based on observations with the Karl G. Jansky Very Large Array. The observations were aimed at detecting gas associated with previous or ongoing mass loss. Near the long-period Cepheid TMon, we report the detection of a partial shell-like structure whose properties appear consistent with originating from an earlier epoch of Cepheid mass loss. At the distance of TMon, the nebula would have a mass (H I+He) of~ M 0.5 , or ∼6% of the stellar mass. Assuming that one-third of the nebular mass comprises sweptup interstellar gas, we estimate an implied mass-loss rate of~´-No clear signatures of circumstellar emission were found toward ζGem, RSPup, or XCyg, although in each case, line-of-sight confusion compromised portions of the spectral band. For the undetected stars, we derive model-dependent s 3 upper limits on the mass-loss rates, averaged over their lifetimes on the instability strip, of ´-10 6 ( -) yr −1 and estimate the total amount of mass lost to be less than a few percent of the stellar mass.

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Extended envelopes around Galactic Cepheids

Cited by 32 publications

References 41 publications

Observational calibration of the projection factor of Cepheids

Observational calibration of the projection factor of Cepheids

Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS)

A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS

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