Work Package number: WP2
Work Package title: Exploitation of the pulsating frequency content in rapidly rotating pulsating stars
Lead partner: IA-CAUP
Participants and person/months per participant:

• IA-CAUP:
• CSIC:
• UGR:
• ULG:
• IRAP:
• INTA:

Objectives:

• Objective 2.1: Identify and highlight the differences between the real pulsating spectra of rapidly rotating stars and the corresponding models.
• Objective 2.2: Develop tools for the extraction of useful physical information from the frequency sets.
• Objective 2.3: Creating an open-source and web-based version of the tools developed in the previous objectives.

Description of the work:

The analysis of pulsations in rapidly rotating stars has been a main difficulty in the last decades. The principal obstacle was the lack of an appropiate theory of both pulsations and stellar structure of rapidly rotating stars. Now, theory and computation resources have changed the situation. Recently developed 2D codes for accounting for the deformation of rapid rotators and the consequences on their pulsations, namely ESTER (reference) and TOP (reference) codes, respectively, shed light over this problem. An unexpected result stemmed from these calculations was the complexity of the new distribution and number of modes that appeared in the frequency spectra of the models., complicated any direct comparison between theory and observations.

On the other hand, high precise photometry coming from recent space missions (MOST, CoRoT and Kepler) revealed a really rich pulsating spectra for some rapidly rotating stars (Poretti et al. 2009; García Hernández et al. 2009). Moreover, the presence of gaps in the light curves of such quality have a enormous impact in the extraction of the pulsating frequencies (reference, Pascual-Granado et al.). And the excellent precision reached with space data set out new difficulties in deriving the frequencies with the classical analysis tools (Balona 2015).

All these facts made a direct comparison of computed and observed modes unfruitful (reference?). Fortunately, some statistical techniques have been shown to be useful for the extraction of information from the observed frequency distribution (García Hernández et al. 2009; García Hernández et al. 2013; others). The information, in form of patterns, was also predicted by the recent 2D models (Lignières et al. 2006; Lignières et al. 2010; Reese et al. 2008 (? Check) ).

In this workpage we plan to study and develope all the tools that can be used to derive some information from the frequency content, both for the p-mode regime and for the g-mode regime. To that end, comparison between observations and models will be essential. Once we developed and tested the robustness of the tools, we will make them publicly available and we will implement them in a web-based enviroment through the Virtual Observatory.

Tasks

• Task 2.1: Study the impact of the presence of spurious peaks within the frequency specrtum in the determination of patterns
• Task 2.2: Study statistically the accuracy (uncertainty? robustness?) of the method for searching frequency patterns (large separation)
• Task 2.3: Study other possible periodicities in the light curve (for example, modulation) feasible to be compared with the theory
• Task 2.4: Adapt the mehod for determining periodicities on the p-mode region to the g-modes
• Task 2.5: Develop a web-version of the tools for the seach of periodicities
• Task 2.6: Study the evolution of the different periodicities with rotation (obsevational and theoretically)
• Task 2.7: Seismic indices?

Milestones


Deliverables

• D2.1 Webtools (Fourier transform, histogram of frequency differencies and Echelle diagram) to search for the large separation in a frequency set
• D2.2 Webtools for the search for the rotational splitting
• D2.3 Webtools for the analysis of patterns in the g-mode regime (periods)
• D2.4 Report?

Risks