arXiv subjects

Maria Pia Di Mauro

Publications and source records attributed to Maria Pia Di Mauro.

12 recordsLinked to original sources

arXiv2026

Chemical paradox in a binary system: Exploring metal enrichment in HD 81809B

The HD 81809 system presents peculiar chemical composition with a large metallicity difference between its two components: the primary has low metallicity ([Fe/H]=-0.57 dex), while the secondary has approximately solar metallicity ([Fe/H]=0.0 dex). This study investigates whether the chemical enrichment of HD 81809B can be reconciled by a planetary engulfment event, consistent with the star's evolutionary constraints. Using Modules for Experiments in Stellar Astrophysics (MESA) code, we model HD 81809B introducing accretion events with different ranges of masses and chemical mixtures to understand their impact in the surface chemical composition. Our simulation shows that reproducing the observed surface [Fe/H] in HD 81809B requires a substantial accretion event. To reach the observed metallicity, the star must engulf 25 to 75 $M_\oplus$ of metals near its current age. Accretion brings the effective temperature of stellar models closer to the observed one; however, the lithium results over-enriched. In order to reproduce the abundance of this element, the star must accrete less than 6 $M_\oplus$. These results suggest that a planetary accretion event is plausible in the evolution of HD 81809B; however, the chemical composition of the accreted material may differ from the assumptions adopted here. Nevertheless, this study emphasizes the importance of considering such external events when modeling chemically anomalous binary systems.

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arXiv2026

Core-envelope coupling of gravito-inertial waves in pre-main-sequence solar-type stars

After the recent detection of solar equatorial Rossby waves, a renewed interest has been brought to the study of gravito-inertial waves propagating in the convective envelope of solar-type stars. In particular, the ability that some of these envelope gravito-inertial modes have to couple with the ones trapped in the radiative interior might open new windows to probe the deep-layer dynamics of solar-type stars. The possibility for such a coupling to occur is particularly favoured in pre-main sequence (PMS) solar-type stars. Indeed, due to the contraction of the protostellar object, they are able to reach large rotation frequencies before nuclear reactions are ignited and magnetic braking becomes the driving mechanism for their rotational evolution. In this work, we therefore study the coupling between the envelope inertial waves and the radiative interior g modes in PMS stars, focusing on the case of prograde dipolar modes. We consider the case of 0.5 Msun and 1 Msun PMS models, each with three different scenarios of rotational evolution. We show that, for stars that have formed with a sufficient amount of angular momentum, this coupling can occur in frequency ranges that are accessible to space-borne photometry, creating inertial dips in the period spacing pattern. With an asymptotic analysis we characterise the shape of these inertial dips to show that they depend on rotation and on the stiffness of the convective-radiative interface.

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arXiv2026

On the contradictory case of the binary system HD 81809 hosting two pulsating solar-like stars observed by TESS

We present a new comprehensive study of HD81809, a nearby binary system of two solar-like stars showing high-amplitude X-ray emission and a well-defined 8-year solar-like magnetic cycle. By analyzing high-resolution spectroscopy, alongside DR3 Gaia astrometry, and bolometric fluxes, we derive updated fundamental parameters for both components. In particular, we uncover a significant chemical difference: the primary is metal-poor ([Fe/H]$ \simeq - 0.57$), while the secondary shows solar-like metallicity ([Fe/H]$=0.00$). This suggests that the system originated in a mildly metal-poor environment, consistent with the Galactic thick disk population, and that the secondary's surface composition has been altered by a recent accretion event. Using multi-sector TESS photometry, we detected solar-like oscillations in both components, deriving global asteroseismic parameters $Δν= 43.32 \pm 3.91 μ$Hz, $ν_{\rm max} = 708.74^{+3.23}_{-3.74} μ$Hz for HD81809 A, and $Δν= 97.75 \pm 4.49~μ$Hz, $ν_{\rm max} = 2098.07^{+3.07}_{-2.83} μ$Hz for HD81809 B. By combining all the observational constraints with stellar evolutionary models computed using CLES and MESA codes, we reconstructed the evolutionary scenario of the system. Our results indicate that HD 81809 is an old system with an age of $\sim 10 \mathrm{Gyr}$, composed of a subgiant primary with mass $\sim 0.87M_{\odot}$ and radius $\sim1.96R_{\odot}$ - likely responsible for the reactivated dynamo cycle - and a main sequence secondary with mass $ M=0.85M_{\odot}$ and radius $R=1.10R_{\odot}$. This system represents a benchmark for studying stellar evolution, magnetic activity, and the physics of old, metal-poor stars in the Galactic thick disk.

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arXiv2026

Studying the surface effect in Procyon A as an F-type star

Procyon A is an F-type main-sequence star in a binary system. It has been the subject of numerous ground-based and space-based observing campaigns, providing precise classical constraints, including a well-determined mass. It was also among the first stars in which individual frequencies were detected, making it a crucial benchmark for F-type stars. Our goal is to investigate the surface effect, namely the discrepancy between observed and model oscillation frequencies due to inadequate modeling of the surface stellar layers, especially important in F-type stars. Using Procyon A as a case study, we aim to understand how different surface correction prescriptions impact the inference of the fundamental properties of this star, and compare the results with those obtained when the surface corrections are neglected. We inferred the fundamental stellar properties employing a grid of models computed with MESA, including gravitational settling, radiative accelerations, and turbulent mixing. We selected the best-fit models using the AIMS code taking into account different methods to fit the individual frequencies. We find that the use of surface corrections can introduce uncertainties up to 7\% in the inferred stellar mass. We identify that the most reliable stellar mass estimates are obtained when using frequency ratios, the Sonoi et al. (2015) surface correction or directly fitting the individual frequencies. Our results indicate that the surface effects in F-type stars differ from those found in the Sun and in solar-like stars, highlighting the need to be careful when considering the surface corrections for these stars.

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arXiv2023

The exoplanetary magnetosphere extension in Sun-like stars based on the solar wind -- solar UV relation

The Earth's magnetosphere extension is controlled by the solar activity level via solar wind properties. Understanding such a relation in the Solar System is important for predicting also the condition of exoplanetary magnetospheres near Sun-like stars. We use measurements of a chromospheric proxy, the Ca II K index, and solar wind OMNI parameters to connect the solar activity variations, on the decennial time scales, to the solar wind properties. The data span over the time interval 1965-2021, which almost entirely covers the last 5 solar cycles. Using both cross-correlation and mutual information analysis, a 3.2-year lag of the solar wind speed with respect to the Ca II K index is found. Analogously, a 3.6-year lag is found once considering the dynamic pressure. A correlation between the solar wind dynamic pressure and the solar UV emission is found and used to derive the Earth's magnetopause standoff distance. Moreover, the advantage of using a chromospheric proxy, such as the Ca II K index, opens the possibility to extend the relation found for the Sun to Sun-like stars, by linking stellar variability to stellar wind properties. The model is applied to a sample of Sun-like stars as a case study, where we assume the presence of an Earth-like exoplanet at 1 AU. Finally, we compare our results with previous estimates of the magnetosphere extension for the same set of Sun-like stars.

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arXiv2022

On the characterization of GJ 504: a magnetically active planet-host star observed by the Transiting Exoplanet Survey Satellite (TESS)

We present the results of the analysis of the photometric data collected in long and short-cadence mode by the Transiting Exoplanet Survey Satellite (TESS) for GJ 504, a well studied planet-hosting solar-like star, whose fundamental parameters have been largely debated during the last decade. Several attempts have been made by the present authors to isolate the oscillatory properties expected on this main-sequence star, but we did not find any presence of solar-like pulsations. The suppression of the amplitude of the acoustic modes can be explained by the high level of magnetic activity revealed for this target, not only by the study of the photometric light-curve, but also by the analysis of three decades available of Mount Wilson spectroscopic data. In particular, our measurements of the stellar rotational period Prot=3.4 d and of the main principal magnetic cycle of 12 a confirm previous findings and allow us to locate this star in the early main sequence phase of its evolution during which the chromospheric activity is dominated by the superposition of several cycles before the transition to the phase of the magnetic-braking shutdown with the subsequent decrease of the magnetic activity.

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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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arXiv2020

Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $ν$ Indi

Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. While these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to precisely date the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called \textit{Gaia}-Enceladus, leading to a substantial pollution of the chemical and dynamical properties of the Milky Way. Here, we identify the very bright, naked-eye star $ν$\,Indi as a probe of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric, and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be $11.0 \pm 0.7$ (stat) $\pm 0.8$ (sys)$\,\rm Gyr$. The star bears hallmarks consistent with it having been kinematically heated by the \textit{Gaia}-Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 Gyr ago at 68 and 95% confidence, respectively. Input from computations based on hierarchical cosmological models tightens (i.e. reduces) slightly the above limits.

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arXiv2019

A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS

We present the discovery of TOI-197.01, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. TOI-197 (HIP116158) is a bright (V=8.2 mag), spectroscopically classified subgiant which oscillates with an average frequency of about 430 muHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2-minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (2.943+/-0.064 Rsun), mass (1.212 +/- 0.074 Msun) and age (4.9+/-1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (9.17+/-0.33 Rearth) with an orbital period of ~14.3 days, irradiance of 343+/-24 Fearth, moderate mass (60.5 +/- 5.7 Mearth) and density (0.431+/-0.062 gcc). The properties of TOI-197.01 show that the host-star metallicity - planet mass correlation found in sub-Saturns (4-8 Rearth) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ~15%, TOI-197.01 is one of the best characterized Saturn-sized planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.

astro-ph.EP↗

arXiv2017

A review on Asteroseismology

Over the last decade, thanks to the successful space missions launched to detect stellar pulsations, Asteroseismology has produced an extraordinary revolution in astrophysics, unveiling a wealth of results on structural properties of stars over a large part of the H-R diagram. Particularly impressive has been the development of Asteroseismology for stars showing solar-like oscillations, which are excited and intrinsically damped in stars with convective envelopes. Here I will review on the modern era of Asteroseismology with emphasis on results obtained for solar-like stars and discuss its potential for the advancement of stellar physics.

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arXiv2011

Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars

Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained with the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly about 50 seconds) and those that are also burning helium (period spacing about 100 to 300 seconds).

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arXiv2008

On the opacity change required to compensate for the revised solar composition

Recent revisions of the determination of the solar composition have resulted in solar models in marked disagreement with helioseismic inferences. The effect of the composition change on the model is largely caused by the change in the opacity. Thus we wish to determine an intrinsic opacity change that would compensate for the revision of the composition. By comparing models computed with the old and revised composition we determine the required opacity change. Models are computed with the opacity thus modified and used as reference in helioseismic inversions to determine the difference between the solar and model sound speed. An opacity increase varying from around 30 per cent near the base of the convection zone to a few percent in the solar core results in a sound-speed profile, with the revised composition, which is essentially indistinguishable from the original solar model. As a function of the logarithm of temperature this is well represented by a simple cubic fit. The physical realism of such a change remains debatable, however.

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