arXiv subjects

Juan Carlos Suárez

Publications and source records attributed to Juan Carlos Suárez.

6 recordsLinked to original sources

arXiv2026

Forward Modeling of the $δ$ Sct Star V1790 Ori: $Δν$, $Ω$, Resolution and Non-adiabatic Effects

We investigate the role of large separation, rotational correction order, structural resolution, and non-adiabatic effects in modelling the rotating $δ$ Scuti star V1790 Ori. From TESS data, we extract 69 frequencies and determine $Δν\simeq 82$ $μ$Hz. Rotating MESA models are computed at low and high resolution; their pulsation frequencies are calculated with GYRE (adiabatic/non-adiabatic, first-order rotation) and FILOU (adiabatic, second-order rotation). Using $Δν$ as a structural constraint is necessary to reduce model degeneracy. For the selected minimum-misfit reference model, considering only the 40 modes with consistent $(n,\ell,m)$ labels, the RMS$_{40}$ theoretical frequency differences are 0.442 $μ$Hz (resolution), 0.062 $μ$Hz (non-adiabatic), and 2.962 $μ$Hz (GYRE vs FILOU); including all 48 frequencies gives RMS$_{48}$ values of 1.033, 2.326, and 3.931 $μ$Hz. Relative to observations, higher resolution reduces residuals from 4.457 to 4.387 $μ$Hz (RMS$_{40}$) and from 4.715 to 4.682 $μ$Hz (RMS$_{48}$); non-adiabatic effects change them marginally to 4.381 and 4.673 $μ$Hz. FILOU gives the largest residuals: 5.331 $μ$Hz (RMS$_{40}$) and 5.270 $μ$Hz (RMS$_{48}$). Second-order rotation produces the largest frequency shifts, but improving agreement with observations requires denser grids and self-consistent FILOU optimisation. The 260.672 $μ$Hz peak -- previously identified as the fundamental radial mode -- shows uncertain identification. The results should be interpreted as diagnostics of modelling systematics and mode-identification robustness.

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arXiv2020

Study of the low-order $Δν$-${\bar ρ}$ relation for moderately-rotating $δ$ Scuti stars and its impact on their characterisation

The large separation in the low radial order regime is considered as a highly valuable observable to derive mean densities of $δ$ Scuti stars, due to its independence with rotation. Up to now, theoretical studies of this $Δν$-${\bar ρ}$ relation have been limited to 1D non-rotating models, and 2D pseudo-evolutionary models. The present work aims at completing this scenario by investigating quantitatively the impact of rotation in this relation on a large grid of 1D asteroseismic models representative of $δ$ Scuti stars. These include rotation effects on both the stellar evolution and the interaction with pulsation. This allowed us to compute the stellar deformation, get the polar and equatorial radii, and correct the stellar mean densities. We found that the new $Δν$-${\bar ρ}$ relation for rotating models is compatible with previous works. We explained the dispersion of the points around the linear fits as caused mainly by the distribution of the stellar mass, and partially by the evolutionary stage. The new fit is found to be close to the previous theoretical studies for lower masses ($1.3-1.81\,\mathrm{M}_{\odot}$). However, the opposite holds for the observations: for the higher masses ($1.81-3\,\mathrm{M}_{\odot}$) the fit is more compatible with the empirical relation. We applied these results to characterise the two well-known $δ$ Scuti stars observed by CoRoT, HD174936 and HD174966, and compared the physical parameters with those of previous works. Inclusion of rotation in the modelling causes a tendency towards greater masses, radii, luminosities and lower density values. Comparison between $Δν$ and Gaia's luminosities also allowed us to constraint the inclination angles and rotational velocities of both stars. The present results pave the way to systematically constrain the angle of inclination of $δ$ Scuti stars

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arXiv2020

Detection and characterisation of oscillating red giants: first results from the TESS satellite

Since the onset of the `space revolution' of high-precision high-cadence photometry, asteroseismology has been demonstrated as a powerful tool for informing Galactic archaeology investigations. The launch of the NASA TESS mission has enabled seismic-based inferences to go full sky -- providing a clear advantage for large ensemble studies of the different Milky Way components. Here we demonstrate its potential for investigating the Galaxy by carrying out the first asteroseismic ensemble study of red giant stars observed by TESS. We use a sample of 25 stars for which we measure their global asteroseimic observables and estimate their fundamental stellar properties, such as radius, mass, and age. Significant improvements are seen in the uncertainties of our estimates when combining seismic observables from TESS with astrometric measurements from the Gaia mission compared to when the seismology and astrometry are applied separately. Specifically, when combined we show that stellar radii can be determined to a precision of a few percent, masses to 5-10% and ages to the 20% level. This is comparable to the precision typically obtained using end-of-mission Kepler data

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arXiv2019

Constraining dark photon properties with Asteroseismology

Dark photons are particles invoked in some extensions of the Standard Model which could account for at least part of the dark matter content of the Universe. It has been proposed that the production of dark photons in stellar interiors could happen at a rate that depends on both, the dark photon mass and its coupling to Standard Model particles (the kinetic mixing parameter $χ$). In this work we aim at exploring the impact of dark photon productions in the stellar core of solar mass RGB stars during late evolutionary phases. We demonstrate that near the so-called RGB bump, dark photons production may be an energy sink for the star sufficiently significative to modify the extension of the star convective zones. We show that Asteroseismology is able to detect such variations in the structure, allowing us to predict an upper limit of $\rm 900\ eV$ and $5\times 10^{-15}$ for the mass and kinetic mixing of the dark photons, respectively. We also demonstrate that additional constraints can be derived from the fact that dark photons increase the luminosity of the RGB tip over the current observational uncertainties. This work thus paves the way for an empirical approach to deepen the study of such dark-matter particles.

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arXiv2019

Chronos --- Taking the pulse of our Galactic neighbourhood (ESA Voyage 2050 White Paper)

The period 2035-50 considered in the ESA Voyage long-term plan will coincide with a series of foreseeable advances in the characterization of the stellar content of the Milky Way. The Gaia mission, combined with large-scale spectroscopic surveys, is helping to build an unprecedented census in terms of the astrometric, kinematic and chemical properties of Galactic stellar populations. Within a decade, precise measurements of such properties will be available for hundreds of millions of stars. Meanwhile, time-domain surveys initiated with CoRoT and Kepler/K2 and carried on by space missions such as TESS and PLATO or ground-based projects like the LSST, will have brought asteroseismology to a high level of maturity. The combination of precise ages from asteroseismology with astrometric and spectroscopic data, on large stellar samples, is allowing Galactic archaeologists to gain new insight into the assembly history of the Milky Way. Recent breakthroughs --- based on the detection of solar-like oscillations in tens of thousands of red-giant stars --- demonstrate the potential of such approach. Therefore, we are convinced that an all-sky, high-cadence, long-duration stellar variability survey will become a scientific priority in the 2035-50 period. The Chronos concept presented here consists in a time-domain extension to Gaia. It will allow for mass and age estimates for half a million red giants within 1.7 kpc from the Sun and hence shed a new light on our understanding of the Galactic dynamics and archaeology. In terms of the targeted pulsators, Chronos will bridge the gap between PLATO and the LSST by surveying stars all the way from the subgiant branch to the early AGB. Finally, it will surpass all previous surveys capable of conducting asteroseismology in terms of the combined sky coverage and duration of the observations (2 x 3.75 months over the whole sky and >5 years in the CVZ).

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arXiv2015

Observational $Δν$-$\barρ$ relation for $δ$ Sct stars using eclipsing binaries and space photometry

Delta Scuti ($δ$ Sct) stars are intermediate-mass pulsators, whose intrinsic oscillations have been studied for decades. However, modelling their pulsations remains a real theoretical challenge, thereby even hampering the precise determination of global stellar parameters. In this work, we used space photometry observations of eclipsing binaries with a $δ$ Sct component to obtain reliable physical parameters and oscillation frequencies. Using that information, we derived an observational scaling relation between the stellar mean density and a frequency pattern in the oscillation spectrum. This pattern is analogous to the solar-like large separation but in the low order regime. We also show that this relation is independent of the rotation rate. These findings open the possibility of accurately characterizing this type of pulsator and validate the frequency pattern as a new observable for $δ$ Sct stars.

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