arXiv subjects

C. Aguilera-Gómez

Publications and source records attributed to C. Aguilera-Gómez.

5 recordsLinked to original sources

arXiv2026

Dynamical constraints on planet engulfment as the origin of lithium enhancement in TOI-5882

As stars evolve off the main sequence, changes in stellar structure can alter the dynamical architecture of planetary systems and, in some cases, lead to planet engulfment events capable of producing observable chemical signatures such as lithium enhancement. TOI-5882 is a lithium-rich subgiant hosting a 22 m_Jup brown dwarf on a 7.1-day orbit, where the enrichment could plausibly result from the recent engulfment of a super-Earth to Neptune-mass planet. We assess the dynamical viability of a planet engulfment scenario in the TOI-5882 system that could explain its observed Li enrichment. We combine stellar evolution models with N-body simulations that incorporate time-dependent stellar properties as the host star leaves the main sequence, exploring a broad range of pre-engulfment planetary masses and orbital configurations. Planet engulfment is the most probable outcome under the explored configurations. However, only 5% of the simulations produce engulfment within the short detectability window of the lithium-enrichment signature. Engulfment therefore remains a viable explanation for the observed Li enhancement in TOI-5882, but only for a relatively uncommon subset of the initial conditions considered here. Under our simplified architecture, recent engulfment cannot be ruled out as the origin of the observed lithium enhancement. However, because successful cases represent only a small fraction of the initial conditions explored here, and because additional processes such as wind-induced drag forces were not included, additional constraints on the system's primordial architecture are needed to assess how likely this scenario is for TOI-5882.

astro-ph.EP↗

arXiv2025

Gaia FGK Benchmark Stars: spectral library, metallicities and abundances of $α$ and Fe-peak elements of the third version

The accurate determination of chemical abundances in stars plays a pivotal role in understanding stellar structure and evolution, nucleosynthesis, and the chemical enrichment history of the Milky Way. Benchmark stars with precise and accurate atmospheric parameters and abundances are indispensable for calibrating spectroscopic surveys and testing stellar atmosphere models. This study focuses on the compilation of high-quality spectra and the determination of LTE chemical abundances of iron-peak and $α$ elements for the third version of the Gaia FGK Benchmark Stars (GBSv3). We compiled spectra of the GBSv3 from public archives and complemented these with our own observations. We use fundamental atmospheric parameters from Soubiran et al. 2024 to derive the chemical abundances and perform a spectroscopic analysis using the public code iSpec. We compile a homogeneous spectral library of high-resolution (42,000) and high signal-to-noise ($>100$) normalised spectra for 202 stars: including the 192 GBSv3, 9 stars with indirect measurement of the angular diameter from previous GBS versions, and the Sun. Using four radiative transfer codes, we derive chemical abundances of 13 chemical species (Fe I, Fe II, Mg I, Si I, Ca I, Ti I, Ti II, Sc II, V I, Cr I, Mn I, Co I, Ni I). We make an in-depth study of several sources of error. The GBSv3 contributes to the legacy samples of spectroscopic reference stars with improved statistics and homogeneity. This work offers the community a homogeneous spectral library and robust reference abundances for iron-peak and $α$ elements, supported by an extensive analysis of the associated uncertainties.

astro-ph.SR↗

arXiv2025

Studying stellar populations in Omega Centauri with phylogenetics

The nature and formation history of our Galaxy's largest and most enigmatic stellar cluster, known as Omega Centauri (ocen) remains debated. Here, we offer a novel approach to disentangling the complex stellar populations within ocen based on phylogenetics methodologies from evolutionary biology. These include the Gaussian Mixture Model and Neighbor-Joining clustering algorithms applied to a set of chemical abundances of ocen stellar members. Instead of using the classical approach in astronomy of grouping them into separate populations, we focused on how the stars are related to each other. In this way, we could identify stars that likely formed in globular clusters versus those originating from prolonged in-situ star formation and how these stars interconnect. Our analysis supports the hypothesis that ocen might be a nuclear star cluster of a galaxy accreted by the Milky Way with a mass of about 10^9M_sun. Furthermore, we revealed the existence of a previously unidentified in-situ stellar population with a distinct chemical pattern unlike any known population found in the Milky Way to date. Our analysis of ocen is an example of the success of cross-disciplinary research and shows the vast potential of applying evolutionary biology tools to astronomical datasets, opening new avenues for understanding the chemical evolution of complex stellar systems.

astro-ph.GA↗

arXiv2021

Revisiting neutron starquakes caused by spin-down

Pulsars show a steady decrease in their rotational frequency, occasionally interrupted by sudden spin-ups called glitches, whose physical origin is still a mystery. One suggested explanation for at least the small glitches are starquakes, that is, failures of the solid neutron star crust, in which the progressive reduction in the centrifugal force deforms the star, stressing the solid until it breaks. This produces a spin-up, dissipating energy inside the star. We analyze the deformations produced by the decreasing centrifugal force, modeling the star with a fluid core and a solid crust, each with uniform density and with the core possibly denser than the crust, as a simple approximation to the strong density gradient present in real neutron stars. The deformation is qualitatively different from the previously studied case of equal densities. The former more closely resembles the behavior of a fluid star, in which the core-crust interface is a surface of constant gravitational plus centrifugal potential. Regardless of the uncertain breaking strain, the glitch activity in this model is several orders of magnitude smaller than observed, even if only small glitches are considered. For a large breaking strain, suggested by simulations, glitches due to starquakes could be roughly of the correct size but much less frequent than observed glitches. The energy released in each glitch is much larger than in the model of angular momentum transfer from a faster rotating superfluid in the inner crust. On the other hand, we cannot rule out that the heating produced by small starquakes could trigger glitches by allowing neutron superfluid vortices to move. We also confirm that stresses in the neutron star crust can in principle support an ellipticity much larger than some observational upper limits from pulsar timing and continuous gravitational wave searches.

astro-ph.HE↗

arXiv2020

Four Jovian planets around low-luminosity giant stars observed by the EXPRESS and PPPS

We report the discovery of planetary companions orbiting four low-luminosity giant stars with M$_\star$ between 1.04 and 1.39 M$_\odot$. All four host stars have been independently observed by the EXoPlanets aRound Evolved StarS (EXPRESS) program and the Pan-Pacific Planet Search (PPPS). The companion signals were revealed by multi-epoch precision radial velocities obtained during nearly a decade. The planetary companions exhibit orbital periods between $\sim$ 1.2 and 7.1 years, minimum masses of m$_{\rm p}$sini $\sim$ 1.8-3.7 M$_{jup}$ and eccentricities between 0.08 and 0.42. Including these four new systems, we have detected planetary companions to 11 out of the 37 giant stars that are common targets between the EXPRESS and PPPS. After excluding four compact binaries from the common sample, we obtained a fraction of giant planets (m$_{\rm p} \gtrsim$ 1-2 M$\_{jup}$) orbiting within 5 AU from their parent star of $f = 33.3^{+9.0}_{-7.1} \%$. This fraction is significantly higher than that previously reported in the literature by different radial velocity surveys. Similarly, planet formation models under predict the fraction of gas giant around stars more massive than the Sun.

astro-ph.EP↗