CoRoT 102918586: a γ Doradus pulsator in a short-period eccentric eclipsing binary

2015

Astron Nachr

We provide a status report on the determination of stellar ages from asteroseismology for stars of various masses and evolutionary stages. The ability to deduce the ages of stars with a relative precision of typically 10 to 20 % is a unique opportunity for stellar evolution and also of great value for both galactic and exoplanet studies. Further, a major uncalibrated ingredient that makes stellar evolution models uncertain, is the stellar interior rotation frequency Ω(r) and its evolution during stellar life. We summarize the recent achievements in the derivation of Ω(r) for different types stars, offering stringent observational constraints on theoretical models. Core-to-envelope rotation rates during the red-giant stage are far lower than theoretical predictions, pointing towards the need to include new physical ingredients that allow strong and efficient coupling between the core and the envelope in the models of low-mass stars in the evolutionary phase prior to core helium burning. Stars are subject to efficient mixing phenomena, even at low rotation rates. Young massive stars with seismically determined interior rotation frequency reveal low core-to-envelope rotation values. Asteroseismology: the new route for stellar physicsContemporary stellar structure and evolution theory still has several open questions, the answers having vast implications for exoplanetary, supernova, and (extra)galactic science. One major uncalibrated quantity is the rotation frequency in the stellar interior throughout stellar life. Also the level of chemical mixing inside stars is hard to judge from surface abundance measurements. While models of stars not too different from the Sun in terms of mass, rotation, and evolutionary stage are well scalable from the solar model, this is far less so for stars with appreciably different properties such as high mass, rapid rotation, strong wind, evolved status, etc.A recent driver to improve stellar physics is the availability of long-duration high-cadence quasi-uninterrupted white-light space photometry with a precision of μmag as- ) satellites. This offered the opportunity to confront stellar models with asteroseismic data. This is done by computing the predicted spectrum of normal oscillation modes from theoretical models, by considering small perturbations to the equations of stellar structure, usually in the approximation of a spherically symmetric star. Normal modes are either pressure (p-)modes or gravity (g-)modes, depending Corresponding author: Conny.Aerts@ster.kuleuven.be on whether the pressure force, respectively buoyancy, is the dominant restoring force. Pressure modes probe the stellar envelope while g-modes tune the inner part of star. Such seismic diagnostics are far more suitable to probe stellar interiors compared to measurements of surface quantities. Figure 1 shows part of a typical Kepler light curve for a newly discovered g-mode pulsator, as well as the frequency spectrum based on the entire light curve in the range of maximum amplitude. An extensive description of t...

Section: Tidal Asteroseismologymentioning

confidence: 96%

The age and interior rotation of stars from asteroseismology

2015

Astron Nachr

“…Currently, only a few γ Dor pulsators in double-lined spectroscopic binaries are known, making their analysis very relevant for asteroseismology. Maceroni et al (2013) studied a γ Dor pulsator in an eccentric binary system, observed by CoRoT. Here, we are dealing with a non-eccentric system with a longer orbital period.…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

“…In each step of the procedure, we used the entire Q1-Q10 dataset without any rebinning. Our iterative method is similar to the one described in Maceroni et al (2013) and consists of the following steps:…”

Section: Binary Modelmentioning

confidence: 99%

KIC 11285625: A double-lined spectroscopic binary with aγDoradus pulsator discovered fromKeplerspace photometry

Debosscher

Tkachenko

et al. 2013

A&A

Self Cite

Aims. We present the first binary modelling results for the pulsating, eclipsing binary KIC 11285625 that was discovered by the Kepler mission. An automated method to disentangle the pulsation spectrum and the orbital variability in high quality light curves was developed and applied. The goal was to obtain accurate orbital and component properties in combination with essential information derived from spectroscopy. Methods. A binary model for KIC 11285625 was obtained, using a combined analysis of high-quality space-based Kepler light curves and ground-based high-resolution HERMES echelle spectra. The binary model was used to separate the pulsation characteristics from the orbital variability in the Kepler light curve in an iterative way. We used an automated procedure based on the JKTEBOP binary modelling code to perform this task, and adapted codes for frequency analysis and prewhitening of periodic signals. Using a disentangling technique applied to the composite HERMES spectra, we obtained a higher signal-to-noise mean spectrum for both the primary and the secondary components. A model grid search method for fitting synthetic spectra was used for fundamental parameter determination for both components. Results. Accurate orbital and component properties of KIC 11285625 were derived, and we have obtained the pulsation spectrum of the γ Dor pulsator in the system. Detailed analysis of the pulsation spectrum revealed amplitude modulation on a timescale of a hundred days, and strong indications of frequency splittings at both the orbital frequency and the rotational frequency derived from spectroscopy.

“…Even if the data analysis can be successfully accomplished, challenges are faced with the physical interpretation, particularly in the cases where tidally excited g-mode oscillations occur amidst (unidentified) free oscillations of (one of) the components in eccentric systems or when reflection effects are so strong that asymmetrically heated atmosphere models must be used before seismic interpretations can be attempted. Examples of eclipsing binaries with a mainsequence pulsator are, e.g., HD 174884 (Maceroni et al 2009), CoRoT 102918586 (Maceroni et al 2013), KIC 10661783 (Southworth et al 2012, Lehmann et al 2013, and KIC 4544587 (Hambleton et al 2013). The compact subdwarf pulsator 2M1938+4603 requires a new generation of atmosphere models before a solid interpretation can be made (Østensen et al 2010).…”

Section: Eclipsing Binaries: Complications and Opportuntiesmentioning

confidence: 99%

Asteroseismology of binary stars and a compilation of core overshoot and rotational frequency values of OB stars

EAS Publications Series

2013

Abstract. After a brief introduction into the asteroseismic modelling of stars, we provide a compilation of the current seismic estimates of the core overshooting parameter and of the rotational frequency of single and binary massive stars. These important stellar parameters have meanwhile become available for eleven OB-type stars, among which three spectroscopic pulsating binaries and one magnetic pulsator. We highlight the potential of ongoing and future analyses of eclipsing binary pulsators as essential laboraties to test stellar structure and evolution models of single and binary stars.