Title: Characterization of stellar magnetic activity in solar-like stars through fractal analysis
PI: Javier Pascual Granado
Abstract: Fractal characterization of stellar light curves could potentially serve as a of stellar magnetic activity. We would like to test the goodness of the fractal power fraction as calculated by CGSA technique for the estimation of the intensity of magnetic activity in a broad sample of solar-like stars. We need an initial set of well-studied stars to be used as validation set whose magnetic activity has already been estimated with other techniques. We also need to prepare a sample of light curves to be used as test.
Title: Gravity-darkening effect and age determination for thousands of delta Scuti stars
PI: Sebastià Barceló Forteza
Abstract: Higher rotation rates produce more flattened stars and temperature gradients by latitude. Then, photometric and spectroscopic measurements are tainted by extrinsic parameters as inclination or extinction. Recent studies suggest this is not the case for seismic indexes. Our aim is to know how these measurements affect age determination. For that purspose, we will correct photometric temperature from gravity-darkening effect obtaining rotation and large separation for huge sample of delta Scuti stars.
Title: Analysis of the visual binary roAp-dSct system TIC394124612
PI: Antonio García Hernández
Abstract: TIC394124612 (HD218994) is a known visual binary system with a roAp and a Delta Scuti component. This binary is particularly interesting because of the insights it can provide into the problem of evolution of chemical perculiar and magnetics stars. We propose an analysis of the oscillation spectra of both pulsating stars and some oscillation and evolutionary models to understand how the joint evolution of the system could be.
Title: Using VO tools to solve the 29 Cygni puzzle
PI: José Ramón Rodón Ortiz
Abstract: 29 Cygni is a chemically peculiar A2V star of the λ Bootis type showing deficiencies in iron-peak elements. It is also a δ Scuti pulsating star located on the blue side of the δ Scuti instability strip in the HR diagram. This makes it an ideal objective to study the λ Bootis phenomenon because it is possible to perform asteroseismic studies. Large variations in the far ultraviolet spectral energy distribution of 29 Cyg have been found recently . Several scenarios have been proposed which could account for the far UV variability of 29 Cygni: change in effective temperature throughout the pulsational cycle, an accretion of circumstellar grains onto the photosphere or the transit of an hitherto unknown stellar companion, but all these hypotheses seem unlikely. Here we will use VO to search for stars similar to 29 Cyg and compare their variability in their UV spectra to find patterns that can be used to shed some light into this problem.
Title: Plato Light Curves preparation
PI: Andy Moya
Abstract: Plato WP128.300 is devoted to the preparation of the LCs for asteroseismology. Part of the most relevant tools for this task are present at this Iberian Meeting. We plan to discuss the current results found in the context of this WP and design the next steps focussing on transits removal and gap filling.
Title: Time-frequency analysis of the pulsation spectra of delta scuti stars
PI: Alejandro Ramón Ballesta
Abstract: The stability in time of the pulsation frequencies of delta-sct stars is unknown. There are some tools like the Wavelet Transform or the Short Time Fourier Transform that might prove useful for such analysis. But these methods have their drawbacks. In this project I would like to discuss these methods (or any other that may arise in the discussion) to analyse the time-frequency variability.
Title: Phase patterns of non-linearities: the problem of the subtraction combinations
PI: Mariel Lares Martiz
Abstract: Combination frequencies can be footprints of non-linear effects within a pulsating star. To unambiguously identify this nature of a combination frequency, one can study the phase relations between the pulsating modes (parents) and their combinations (children). When studying these relationships in clear cases of combination frequencies due to non-linear mixing of the modes (e.g in HADS), an evident pattern is obtained for sum and harmonic children. Conversely, the phase relationships between parents and the children that come from subtraction operations seem to behave differently. Solving this issue could would help to set the foundations of the theory for non-linear light curves characterization
Title: How to best prepare TESS 2-min cadence light curves of solar-type stars for seismic analysis?
PI: Thibault Boulet
Abstract: There are two types of light curves available: SAP flux is Simple Aperture Photometry flux:Light curve files contain flux time series data and are produced for each target using simple aperture photometry. TESS light curves are FITS format files that contain the output of the photometric extraction and subsequent systematics removal (cotrending) performed by the SPOC algorithms. PDCSAP is the Pre-search Data Conditioning SAP flux: Long term trends have been removed from this data using so-called Cotrending Basis Vectors (CBVs). Co-trending basis vectors (CBVs) represent the set of systematic trends present in the ensemble flux data. CBVs are provided for each operational sector of the mission. These are derived by the TESS pipeline from a Principle Component Analysis and used to mitigate systematic artifacts within the target light curves.
Which type of light curves is most adequate to perform asteroseismology of solar-type stars? What sort of post-processing is most adequate? What sort of filtering? What sort of outlier removal? What sort of stitching?
The goal is to download 5 reference multi-sector light curves clearly revealing oscillations and compare the results of our post-processing: The light-curves are available on my Git-hub : https://github.com/AmiralVespasien3/Iberian-Project
TIC 150030411 TIC 150062447 TIC 150166759 TIC 150393198 TIC 167548586.
Title: Modellation of the Mixed Modes of Garfield
PI: Miguel Tavares Clara
Abstract: The best characterizations of stars require a good grid of stellar models and a list of seismic frequencies and classical observables to constraint such optimization. This is especially relevant for the mixed modes of more-evolved stars, which, due to their fast variation, tend to render the interpolation process to be less precise. Until now, we have been working on the optimization of 6 artificial stars generated as part of the PLATO WP124 hares and hounds exercise, while trying to retrieve their associated stellar parameters (mass, radius, and age) with the AIMS optimization code within the scientific requirements defined for the PLATO mission, with a special focus on one, Garfield. Our simulations resulted in accurate values when only ell=0 radial modes were considered, but inconsistencies became constant when non-radial modes were introduced. Simulations with ell=0,1,2 modes present degenerate solutions, while simulations with ell=0,2 modes (in this case, none seem to be mixed modes) present incongruent PDFs and shift parameter values. We ask for other investigators to use their optimization tools to retrieve the true stellar parameters of this star considering the following cases for the seismic constraints: (i) all l=0,2 modes and (ii) all l=0,1,2 modes as seismic constraints, so that we could compare with other results and better understand ours.
Title: TESS FFI red-giant light curve corrections
PI: Filipe Pereira
Abstract: Extracted light curves of TESS FFI targets have systematics that can mimic stellar or planetary signals (TESS's data uplink). The objective of this project is to discuss methods and strategies for removing systematics from light curves of red-giant stars observed by the TESS mission, focusing on both asteroseismology and exoplanetary searches. As examples that highlight some possible issues in the light curves, I have identified 6 TESS targets to focus on during the project, and have the light curves ready to be shared with all participants. The targets TICs are 101007227, 101004338, 61776, 97614, 77393213 and 77397761.
Title: Pulsating stars and new physics
PI: Adrián Ayala Gómez
Abstract: Bounds on dark matter candidates and other new particles have been derived from astrophysical observations. We aim to use Asteroseismology of evolved stars (namely RGBs) in order to look into the impact on asteroseismic observables of the production and emission of dark matter particles from stellar cores. For the goals of this project, catalogs containing precise asteroseismic data, as well as the development of tools to deal with the uncertainties coming from stellar astrophysics, will be of utmost importance.