Understanding the dynamical structure of pulsating stars

Nardetto, N.; Poretti, E.; Rainer, M.; Guiglion, G.; Scardia, M.; Schmid, V. S.; Mathias, P.

doi:10.1051/0004-6361/201322356

Cited by 12 publications

(16 citation statements)

References 47 publications

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“…Another explanation could be secular radius variations; however, V335 Pup exhibits a reversal of the modulation, which may point to a recurrent phenomenon. Another possibility are non-radial pulsations that may manifest themselves as cycle-to-cycle variations in RVs (Kovtyukh et al 2003;Nardetto et al 2014). Strange pulsation modes (Buchler et al 1997;Buchler & Kolláth 2001) could also provide an explanation, since the predicted amplitudes are similar to the observed modulations.…”

Section: Discussionmentioning

confidence: 87%

Tuning in on Cepheids: Radial velocity amplitude modulations

Anderson

2014

A&A

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Context. Classical Cepheids are crucial calibrators of the extragalactic distance scale. The Baade-Wesselink technique can be used to calibrate Cepheid distances using Cepheids in the Galaxy and the Magellanic Clouds. Aims. I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances.Methods. Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear radius variations derived from observations obtained at different epochs. Different timescales are sampled, ranging from cycle-to-cycle to months and years. Results. The unprecedented combination of excellent phase coverage obtained during multiple epochs and high precision enabled the discovery of significant modulation in the RV curves of the short-period s-Cepheids QZ Normae and V335 Puppis, as well as the long-period fundamental mode Cepheids Carinae and RS Puppis. The modulations manifest as shape and amplitude variations that vary smoothly on timescales of years for short-period Cepheids and from one pulsation cycle to the next in the long-period Cepheids. The order of magnitude of the effect ranges from several hundred m s −1 to a few km s −1 . The resulting difference among linear radius variations derived using data from different epochs can lead to systematic errors of up to 15% for Baade-Wesselink-type distances, if the employed angular and linear radius variations are not determined contemporaneously. Conclusions. The different natures of the Cepheids exhibiting modulation in their RV curves suggests that this phenomenon is common. The observational baseline is not yet sufficient to conclude whether these modulations are periodic. To ensure the accuracy of Baade-Wesselink distances, angular and linear radius variations should always be determined contemporaneously.

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Section: Discussionmentioning

confidence: 87%

Tuning in on Cepheids: Radial velocity amplitude modulations

Anderson

2014

A&A

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“…A summary of the available predictions and measurements of the p-factors of RS Pup and of the similar long-period Cepheid P. Kervella et al: Projection factor of the long-period Cepheid RS Pup Burki et al (1982) 1.36 1.36 Hindsley & Bell (1986) 1.341 1.343 Gieren et al (2005) 1.337 ± 0.038 1.347 ± 0.037 Groenewegen (2007) a 1.270 ± 0.050 1.270 ± 0.050 Laney & Joner (2009) 1.196 ± 0.038 1.201 ± 0.036 Storm et al (2011) 1.249 ± 0.105 1.262 ± 0.101 Neilson et al (2012) 1.140 ± 0.003 1.146 ± 0.003 Groenewegen (2013) 1.112 ± 0.030 1.128 ± 0.030 Nardetto et al (2014a) 1.181 ± 0.019 1.186 ± 0.018…”

Section: Discussionmentioning

confidence: 99%

“…A calibration of the p-factor of the intrinsically brightest Cepheids is therefore highly desirable. Theoretical studies (e.g., Neilson et al 2012) indicate that the pfactor may vary with the period, but the dependence differs between authors (Nardetto et al 2014a;Storm et al 2011;Breitfelder et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Observational calibration of the projection factor of Cepheids

Kervella

Trahin

Bond

et al. 2017

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The projection factor (p-factor) is an essential component of the classical Baade-Wesselink (BW) technique, which is commonly used to determine the distances to pulsating stars. It is a multiplicative parameter used to convert radial velocities into pulsational velocities. As the BW distances are linearly proportional to the p-factor, its accurate calibration for Cepheids is of critical importance for the reliability of their distance scale. We focus on the observational determination of the p-factor of the long-period Cepheid RS Pup (P = 41.5 days). This star is particularly important as this is one of the brightest Cepheids in the Galaxy and an analog of the Cepheids used to determine extragalactic distances. An accurate distance of 1910 ± 80 pc (±4.2%) has recently been determined for RS Pup using the light echoes propagating in its circumstellar nebula. We combine this distance with new VLTI/PIONIER interferometric angular diameters, photometry, and radial velocities to derive the p-factor of RS Pup using the code Spectro-Photo-Interferometry of Pulsating Stars (SPIPS). We obtain p = 1.250 ± 0.064 (±5.1%), defined for cross-correlation radial velocities. Together with measurements from the literature, the p-factor of RS Pup confirms the good agreement of a constant p = 1.293 ± 0.039 (±3.0%) model with the observations. We conclude that the p-factor of Cepheids is constant or mildly variable over a broad range of periods (3.7 to 41.5 days).

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“…But Antoci et al (2013) accepted the surface gravity of g log = 3.8 ± 0.2 and were surprised by the absence of solar-like oscillations at a frequency near 43 cd −1 that are predicted using this high value of surface gravity. Nardetto et al (2014) found the surface gravity and the effective temperature of ρ Pup to be equal to g log = 3.42 ± 0.14 and T eff = 6650 ± 100 K, respectively.…”

Section: Chemical Composition Of R Pupmentioning

confidence: 95%

“…Recently, Nardetto et al (2014) analyzed 359 spectra of ρ Pup observed during 5 nights with a spectral resolving power R = 115,000 at the HARPS spectrograph installed at the 3.6 m ESO telescope in La Silla. The exposure times were set as 30 s. The dominant mode of pulsation with frequency 7.098 days −1 with a semiamplitude of the radial velocity curve slightly less than 10 km s −1 and an additional mode with frequency 7.900 days −1 and semiamplitude 0.281 km s −1 were found.…”

Section: Chemical Composition Of R Pupmentioning

confidence: 99%

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

Yushchenko

Gopka

Kang

et al. 2015

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We investigated the chemical composition of ρ Pup using high-resolution spectral observations taken from the Very Large Telescope and the IUE archives and also spectra obtained at the 1.8 m telescope of the Bohyunsan observatory in Korea. The abundances of 56 chemical elements and the upper limits of Li and Be abundances were determined. The abundance pattern of ρ Pup was found to be similar to that of Am-type stars. The possibility of the influence of the accretion of interstellar gas and dust on the abundance patterns of B-F-type stars is discussed. The plots of the relative abundances of chemical elements in the atmospheres of ρ Pup and δ Sct versus the second ionization potentials of these elements show the correlations. The discontinuities at 13.6 and 24.6 eV-the ionization potentials of hydrogen and helium, respectively, are also exhibited in these plots. These discontinuities can be explained by interaction of the atoms of interstellar gas, mainly hydrogen and helium atoms, with the atoms of stellar photospheres (so-called charge-exchange reactions). Note that only the jumps near 13.6 and 24.6 eV were pointed out in previous investigations of relative abundances versus the second ionization potentials for Am-type stars. The dependencies of the relative abundances of chemical elements on the second ionization potentials of these elements were investigated using the published abundance patterns of B-F-type stars. The correlations of relative and absolute abundances of chemical elements, second ionization potentials, and projected rotational velocities are clearly detected for stars with effective temperatures between 7,000 and 12,000 K. If the correlation of relative abundances and second ionization potentials can be explained by the accretion of interstellar gas on the stellar surfaces, the investigation of these correlations can provide valuable information on the density and velocities of interstellar gas in different regions of the Galaxy and also on the influence of this phenomenon on stellar evolution. The dependencies of the relative abundances of chemical elements on the condensation temperatures of these elements were also found in the atmospheres of ρ Pup, δ Sct, and other B-F-type stars. Ten possible λ Boo-type stars were detected. The effective temperatures of these objects are between 10,900 and 14,000 K.

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Understanding the dynamical structure of pulsating stars

Cited by 12 publications

References 47 publications

Tuning in on Cepheids: Radial velocity amplitude modulations

Tuning in on Cepheids: Radial velocity amplitude modulations

Observational calibration of the projection factor of Cepheids

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

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