arXiv subjects

A. Moya

Publications and source records attributed to A. Moya.

At least 19 recordsLinked to original sources

arXiv2026

Two extremely irradiated volatile-rich sub-Neptunes with companions in the TOI-426 and TOI-1839 systems: Insights into arrival and survival near the lower edge of the Neptunian desert

Using TESS photometry and 147 HARPS radial velocities, we confirm two extremely irradiated, volatile-rich sub-Neptunes near the lower edge of the Neptunian desert: TOI-426 b and TOI-1839 b, orbiting the solar-type stars HD 34390 and TYC 304-865-1. We modelled stellar activity with shared-timescale and multidimensional Gaussian processes. The planets have orbital periods of approximately 1.32 and 1.42 days, radii of $2.19\pm0.09$ and $2.27\pm0.10$ Earth radii, and masses of $6.7\pm1.8$ and $7.10\pm0.78$ Earth masses, respectively. They receive approximately 1700 and 1050 times Earth's irradiation, yet their densities require substantial volatile content. We also detect a transiting sub-Neptune, TOI-1839 c, at approximately 4.02 days and a giant companion, TOI-426 c, with a period of $235.8^{+9.2}_{-8.5}$ days and a minimum mass of $444^{+18}_{-17}$ Earth masses, assuming a circular orbit. Interior-structure and atmospheric-escape models yield mass-loss timescales of 1-100 Myr for hydrogen/helium envelopes, compared with 100-1000 Gyr for water-dominated envelopes, favouring a steam-world interpretation for all three transiting planets. A population analysis reveals a striking excess of detected outer giant companions to low-mass sub-Neptunes near the desert edge, where high-eccentricity tidal migration is expected to circularize surviving planets: 36% (9/25) within the tidal survival band versus 6% (9/148) outside it (Fisher exact test $p=1.4\times10^{-4}$). This excess is robust to changes in sample selection and companion definitions. The survival of these volatile-rich planets challenges a boundary set solely by evaporation of primordial hydrogen/helium envelopes, while the companion excess supports an important role for high-eccentricity tidal migration in shaping the lower desert edge.

astro-ph.EP↗

arXiv2025

Characterizing Exoplanets for Assessing Their Potential Habitability

The Statistical-likelihood Exoplanetary Habitability Index (SEPHI) serves as a valuable tool for prioritizing targets for further study and identifying potentially habitable environments. In this paper, we present SEPHI 2.0, which incorporates several key improvements: (1) updated methods for estimating exoplanet internal structures and magnetic fields; (2) the inclusion of orbital eccentricity in assessing the potential for liquid water on an exoplanet's surface; and (3) a new exoplanet mass-radius relationship. SEPHI 2.0 retains its probabilistic framework and combines the different subindexes by selecting the most restrictive one. In SEPHI 2.0, atmospheric retention is consolidated into a single index that incorporates both thermal (Jeans escape) and nonthermal (stellar wind and magnetic effect) processes. Recent advancements in estimating exoplanet internal structures and magnetic fields have been integrated. Additionally, a new empirical exoplanet mass-radius relationship is introduced. All this is incorporated into the SADE code, which uses key data on exoplanets and their host stars to assess habitability and prioritize targets for further study, providing a comprehensive output of an exoplanetary system's physical characteristics. SADE is available as a free online tool. Notably, this is the first approach to including estimated exoplanet magnetic 8elds in a habitability index. The SADE software facilitates the identification of potentially habitable exoplanets. Among the 5500+ confirmed exoplanets, only a few-such as Kepler-62f and GJ 514b achieve SEPHI 2.0 scores close to 1. It is also noticeable that, according to our studies, TRAPPIST-1 f and g are ranked higher than TRAPPIST-1 e in terms of habitability potential.

astro-ph.EP↗

arXiv2024

TOI-5005 b: A super-Neptune in the savanna near the ridge

The Neptunian desert and savanna have recently been found to be separated by a ridge, an overdensity of planets in the period range of $\simeq$3-5 days. These features are thought to be shaped by dynamical and atmospheric processes, but their roles are not yet well understood. Our aim was to confirm and characterize the super-Neptune TESS candidate TOI-5005.01, which orbits a moderately bright (V = 11.8) solar-type star (G2 V) with an orbital period of 6.3 days. We confirm TOI-5005 b to be a transiting super-Neptune with a radius of $R_{\rm p}$ = $6.25\pm 0.24$ $\rm R_{\rm \oplus}$ ($R_{\rm p}$ = $0.558\pm 0.021$ $\rm R_{\rm J}$) and a mass of $M_{\rm p}$ = $32.7\pm 5.9$ $\rm M_{\oplus}$ ($M_{\rm p}$ = $0.103\pm 0.018$ $\rm M_{\rm J}$), which corresponds to a mean density of $\rho_{\rm p}$ = $0.74 \pm 0.16$ $\rm g \, cm^{-3}$. Our internal structure modelling indicates that the overall metal mass fraction is well constrained to a value slightly lower than that of Neptune and Uranus ($Z_{\rm planet}$ = $0.76^{+0.04}_{-0.11}$). We also estimated the present-day atmospheric mass-loss rate of TOI-5005 b, but found contrasting predictions depending on the choice of photoevaporation model. At a population level, we find statistical evidence ($p$-value = $0.0092^{+0.0184}_{-0.0066}$) that planets in the savanna such as TOI-5005 b tend to show lower densities than planets in the ridge, with a dividing line around 1 $\rm g \, cm^{-3}$, which supports the hypothesis of different evolutionary pathways populating the two regimes. TOI-5005 b is located in a key region of the period-radius space to study the transition between the Neptunian ridge and the savanna. It orbits the brightest star of all such planets, which makes it a target of interest for atmospheric and orbital architecture observations that will bring a clearer picture of its overall evolution.

astro-ph.EP↗

arXiv2024

ATAT: Astronomical Transformer for time series And Tabular data

The advent of next-generation survey instruments, such as the Vera C. Rubin Observatory and its Legacy Survey of Space and Time (LSST), is opening a window for new research in time-domain astronomy. The Extended LSST Astronomical Time-Series Classification Challenge (ELAsTiCC) was created to test the capacity of brokers to deal with a simulated LSST stream. We describe ATAT, the Astronomical Transformer for time series And Tabular data, a classification model conceived by the ALeRCE alert broker to classify light-curves from next-generation alert streams. ATAT was tested in production during the first round of the ELAsTiCC campaigns. ATAT consists of two Transformer models that encode light curves and features using novel time modulation and quantile feature tokenizer mechanisms, respectively. ATAT was trained on different combinations of light curves, metadata, and features calculated over the light curves. We compare ATAT against the current ALeRCE classifier, a Balanced Hierarchical Random Forest (BHRF) trained on human-engineered features derived from light curves and metadata. When trained on light curves and metadata, ATAT achieves a macro F1-score of 82.9 +- 0.4 in 20 classes, outperforming the BHRF model trained on 429 features, which achieves a macro F1-score of 79.4 +- 0.1. The use of Transformer multimodal architectures, combining light curves and tabular data, opens new possibilities for classifying alerts from a new generation of large etendue telescopes, such as the Vera C. Rubin Observatory, in real-world brokering scenarios.

astro-ph.IM↗

arXiv2024

Predicted asteroseismic detection yield for solar-like oscillating stars with PLATO

We determine the expected yield of detections of solar-like oscillations for the PLATO ESA mission. We used a formulation from the literature to calculate the probability of detection and validated it with Kepler data. We then applied this approach to the PLATO P1 and P2 samples with the lowest noise level and the much larger P5 sample, which has a higher noise level. We used the information available in in the PIC 1.1.0, including the current best estimate of the signal-to-noise ratio. We also derived relations to estimate the uncertainties of seismically inferred stellar mass, radius and age and applied those relations to the main sequence stars of the PLATO P1 and P2 samples with masses equal to or below 1.2 $\rm{M}_\odot$ for which we had obtained a positive seismic detection. We found that one can expect positive detections of solar-like oscillations for more than 15 000 FGK stars in one single field after a two-years run of observation. For main sequence stars with masses $\leq 1.2 \rm{M}_\odot$, we found that about 1131 stars satisfy the PLATO requirements for the uncertainties of the seismically inferred stellar masses, radii and ages in one single field after a two-year run of observation. The baseline observation programme of PLATO consists in observing two fields of similar size (in the Southern and Northern hemispheres) for two years each. The expected seismic yields of the mission are more 30000 FGK dwarfs and subgiants with positive detections of solar-like oscillations, enabling to achieve the mission stellar objectives. The PLATO mission should produce a sample of seismically extremely well characterized stars of quality equivalent to the Kepler Legacy sample but containing a number of stars $\sim$ 80 times larger if observing two PLATO fields for two years each. They will represent a goldmine which will make possible significant advances in stellar modelling.

astro-ph.SR↗

arXiv2023

The PL diagram for $\delta$ Sct stars: back in business as distance estimators

In this work, we focus on the period-luminosity relation (PLR) of $\delta$ Sct stars, in which mode excitation and selection mechanisms are still poorly constrained, and whose structure and oscillations are affected by rotation. We review the PLRs in the recent literature, and add a new inference from a large sample of $\delta$ Sct. We highlight the difficulty in identifying the fundamental mode and show that rotation-induced surface effects can impact the measured luminosities, explaining the broadening of the PLR. We derive a tight relation between the low-order large separation and the fundamental radial mode frequency (F0) that holds for rotating stars, thus paving the way towards mode identification. We show that the PLRs we obtain for different samples are compatible with each other and with the recent literature, and with most observed $\delta$ Sct stars when taking rotation effects into account. We also find that the highest-amplitude peak in the frequency spectrum corresponds to the fundamental mode in most $\delta$ Sct, thus shedding some light on their elusive mode selection mechanism.

astro-ph.SR↗

arXiv2022

Stellar dating using chemical clocks and Bayesian inference

Dating stars is a major challenge with a deep impact on many astrophysical fields. One of the most promising techniques for this is using chemical abundances. Recent space- and ground-based facilities have improved the quantity of stars with accurate observations. This has opened the door for using Bayesian inference tools to maximise the information we can extract from them. Our aim is to present accurate and reliable stellar age estimates of FGK stars using chemical abundances and stellar parameters. We used one of the most flexible Bayesian inference techniques (hierarchical Bayesian models) to exceed current possibilities in the use of chemical abundances for stellar dating. Our model is a data-driven model. We used a training set that has been presented in the literature with ages estimated with isochrones and accurate stellar abundances and general characteristics. The core of the model is a prescription of certain abundance ratios as linear combinations of stellar properties including age. We gathered four different testing sets to assess the accuracy, precision, and limits of our model. We also trained a model using chemical abundances alone. We found that our age estimates and those coming from asteroseismology, other accurate sources, and also with ten Gaia benchmark stars agree well. The mean absolute difference of our estimates compared with those used as reference is 0.9 Ga, with a mean difference of 0.01 Ga. When using open clusters, we reached a very good agreement for Hyades, NGC 2632, Ruprecht 147, and IC4651. We also found outliers that are a reflection of chemical peculiarities and/or stars at the limit of the validity ranges of the training set. The model that only uses chemical abundances shows slightly worse mean absolute difference (1.18 Ga) and mean difference (-0.12 Ga).

astro-ph.SR↗

arXiv2020

PBjam: A Python package for automating asteroseismology of solar-like oscillators

Asteroseismology is an exceptional tool for studying stars by using the properties of observed modes of oscillation. So far the process of performing an asteroseismic analysis of a star has remained somewhat esoteric and inaccessible to non-experts. In this software paper we describe PBjam, an open-source Python package for analyzing the frequency spectra of solar-like oscillators in a simple but principled and automated way. The aim of PBjam is to provide a set of easy-to-use tools to extract information about the radial and quadrupole oscillations in stars that oscillate like the Sun, which may then be used to infer bulk properties such as stellar mass, radius and age or even structure. Asteroseismology and its data analysis methods are becoming increasingly important as space-based photometric observatories are producing a wealth of new data, allowing asteroseismology to be applied in a wide range of contexts such as exoplanet, stellar structure and evolution, and Galactic population studies.

astro-ph.SR↗

arXiv2020

Alert Classification for the ALeRCE Broker System: The Light Curve Classifier

We present the first version of the ALeRCE (Automatic Learning for the Rapid Classification of Events) broker light curve classifier. ALeRCE is currently processing the Zwicky Transient Facility (ZTF) alert stream, in preparation for the Vera C. Rubin Observatory. The ALeRCE light curve classifier uses variability features computed from the ZTF alert stream, and colors obtained from AllWISE and ZTF photometry. We apply a Balanced Random Forest algorithm with a two-level scheme, where the top level classifies each source as periodic, stochastic, or transient, and the bottom level further resolves each of these hierarchical classes, amongst 15 total classes. This classifier corresponds to the first attempt to classify multiple classes of stochastic variables (including core- and host-dominated active galactic nuclei, blazars, young stellar objects, and cataclysmic variables) in addition to different classes of periodic and transient sources, using real data. We created a labeled set using various public catalogs (such as the Catalina Surveys and {\em Gaia} DR2 variable stars catalogs, and the Million Quasars catalog), and we classify all objects with $\geq6$ $g$-band or $\geq6$ $r$-band detections in ZTF (868,371 sources as of 2020/06/09), providing updated classifications for sources with new alerts every day. For the top level we obtain macro-averaged precision and recall scores of 0.96 and 0.99, respectively, and for the bottom level we obtain macro-averaged precision and recall scores of 0.57 and 0.76, respectively. Updated classifications from the light curve classifier can be found at the \href{http://alerce.online}{ALeRCE Explorer website}.

astro-ph.IM↗

arXiv2020

The Automatic Learning for the Rapid Classification of Events (ALeRCE) Alert Broker

We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self--consistent classification of large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean--led broker run by an interdisciplinary team of astronomers and engineers, working to become intermediaries between survey and follow--up facilities. ALeRCE uses a pipeline which includes the real--time ingestion, aggregation, cross--matching, machine learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp--based classifier, designed for rapid classification, and a light--curve--based classifier, which uses the multi--band flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools and services, which are made public for the community (see \url{https://alerce.science}). Since we began operating our real--time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real--time processing of $9.7\times10^7$ alerts, the stamp classification of $1.9\times10^7$ objects, the light curve classification of $8.5\times10^5$ objects, the report of 3088 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead to go from a single-stream of alerts such as ZTF to a multi--stream ecosystem dominated by LSST.

astro-ph.IM↗

arXiv2020

Unveiling the power spectra of $δ$ Scuti stars with TESS. The temperature, gravity, and frequency scaling relation

Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: $δ$ Scuti stars seem to be characterized with seismic indexes such as the large separation ($Δν$). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power ($ν_{\rm max}$) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of $δ$ Scuti stars seem to be.

astro-ph.SR↗

arXiv2019

Erosion of an exoplanetary atmosphere caused by stellar winds

We present a formalism for a first-order estimation of the magnetosphere radius of exoplanets orbiting stars in the range from 0.08 to 1.3 Mo. With this radius, we estimate the atmospheric surface that is not protected from stellar winds. We have analyzed this unprotected surface for the most extreme environment for exoplanets: GKM-type and very low-mass stars at the two limits of the habitable zone. The estimated unprotected surface makes it possible to define a likelihood for an exoplanet to retain its atmosphere. This function can be incorporated into the new habitability index SEPHI. Using different formulations in the literature in addition to stellar and exoplanet physical characteristics, we estimated the stellar magnetic induction, the main characteristics of the stellar wind, and the different star-planet interaction regions (sub- and super-Alfvénic, sub- and supersonic). With this information, we can estimate the radius of the exoplanet magnetopause and thus the exoplanet unprotected surface. We have conducted a study of the auroral aperture angles for Earth-like exoplanets orbiting the habitable zone of its star, and found different behaviors depending on whether the star is in rotational saturated or unsaturated regimes, with angles of aperture of the auroral ring above or below 36^\circ, respectively, and with different slopes for the linear relation between the auroral aperture angle at the inner edge of the habitable zone versus the difference between auroral aperture angles at the two boundaries of the habitable zone. When the planet is tidally locked, the unprotected angle increases dramatically to values higher than 40^\circ with a low likelihood of keeping its atmosphere. When the impact of stellar wind is produced in the sub-Alfvénic regime, the likelihood of keeping the atmosphere is almost zero for exoplanets orbiting very close to their star.

astro-ph.EP↗

arXiv2019

Abundance to age ratios in the HARPS-GTO sample with Gaia DR2: Chemical clocks for a range of [Fe/H]

[ABRIDGED] The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations to derive stellar ages from chemical abundances. We derive different sets of ages using Gaia parallaxes for a sample of more than 1000 FGK dwarf stars for which he have spectra from the HARPS-GTO program. We analyze the temporal evolution of different abundance ratios to find the best chemical clocks. We find that [$α$/Fe] ratio (average of Mg, Si and Ti), [O/Fe] and [Zn/Fe] are good age proxies with a lower dispersion than the age-metallicity dispersion. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (i.e. low-$α$) but in the case of the chemically defined thick disk stars (i.e. high-$α$) only the elements Mg, Si, Ca and TiII show a clear correlation with age. We find that the thick disk stars are more enriched in light-s elements than thin disk stars of similar age. The maximum enrichment of s-process elements in the thin disk occurs in the youngest stars which in turn have solar metallicity. The slopes of the [X/Fe]-age relations are quite constant for O, Mg, Si, Ti, Zn, Sr and Eu regardless of the metallicity. However, this is not the case for Al, Ca, Cu and most of the s-process elements, which display very different trends depending on the metallicity. This demonstrates the limitations of using simple linear relations based on certain abundance ratios to obtain ages for stars of different metallicities. Finally, we show that by using 3D relations with a chemical clock and two stellar parameters (either Teff, [Fe/H] or stellar mass) we can explain up to 89% of age variance in a star. A similar result is obtained when using 2D relations with a chemical clock and one stellar parameter, being up to a 87% of the variance explained.

astro-ph.SR↗

arXiv2019

Large area photoelectrodes based on hybrids of CNT fibres and ALD grown TiO2

Hybridisation is a powerful strategy towards the next generation of multifunctional materials for environmental and sustainable energy applications. Here, we report a new inorganic nanocarbon hybrid material prepared with atomically controlled deposition of a monocrystalline TiO2 layer that conformally coats a macroscopic carbon nanotube (CNT) fiber. Through X-ray diffraction, Raman spectroscopy and photoemission spectroscopy we detect the formation of a covalent Ti-O-C bond at the TiO2/CNT interface and a residual strain of approximately 0.7-2 \%, which is tensile in TiO2 and compressive in the CNT. It arises after deposition of the amorphous oxide onto the CNT surface previously functionalized by the oxygen plasma used in ALD. These features are observed in samples of different TiO2 thickness, in the range from 10 to 80 nm. Ultraviolet photoemission spectroscopy on a 20 nm-thick TiO2 coated sample gives a work function of 4.27 eV, between that of TiO2 (4.23 eV) and the CNT fiber (4.41 eV), and the presence of new interband gap states that shift the valence band maximum to 1.05 eV below the Fermi level. Photoelectrochemical measurements demonstrate electron transfer from TiO2 to the CNT fiber network under UV irradiation. Electrochemical impedance spectroscopy measurements reveal a low resistance for charge transfer and transport, as well as a large capacitance. Our results point to the fact that these hybrids, in which each phase has nanometric thickness and the current collector is integrated into the material, are very different from conventional electrodes and can provide a number of superior properties.

cond-mat.mtrl-sci↗

arXiv2018

The asteroseismic potential of CHEOPS

Asteroseismology has been impressively boosted during the last decade mainly thanks to space missions such as Kepler/K2 and CoRoT. This has a large impact, in particular, in exoplanetary sciences since the accurate characterization of the exoplanets is convoluted in most cases with the characterization of their hosting star. Until the expected launch of the ESA mission PLATO 2.0, there is almost a decade where only two important missions will provide short-cadence high-precision photometric time-series: NASA--TESS and ESA--CHEOPS missions, both having high capabilities for exoplanetary sciences. In this work, we want to explore the asteroseismic potential of CHEOPS time-series. Following the works done for estimating the asteroseismic potential of Kepler and TESS, we have analyzed the probability of detecting solar-like pulsations using CHEOPS light-curves. Since CHEOPS will collect runs with observational times from hours up to a few days, we have analyzed the accuracy and precision we can obtain for the estimation of nu_max, the only asteroseismic observable we can recover using CHEOPS observations. Finally, we have analyzed the impact of knowing nu_max in the characterization of exoplanet host stars. Using CHEOPS light-curves with the expected observational times we can determine nu_max for massive G and F-type stars from late Main Sequence on, and for F, G, and K-type stars from post-Main Sequence on with an uncertainty lower than a 5%. For magnitudes V<12 and observational times from eight hours up to two days, the HR zone of potential detectability changes. The determination of nu_max leads to an internal age uncertainty reduction in the characterization of exoplanet host stars from 52% to 38%; mass uncertainty reduction from 2.1% to 1.8%; radius uncertainty reduction from 1.8% to 1.6%; density uncertainty reduction from 5.6% to 4.7%, in our best scenarios.

astro-ph.SR↗

arXiv2018

Impact of gaps in the asteroseismic characterization of pulsating stars. I. On the efficiency of pre-whitening

It is known that the observed distribution of frequencies in CoRoT and Kepler δ Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip such as δ Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, just in the range of the pulsational frequency content of the δ Scuti stars, is shown to be crucial to determine their oscillation frequencies, the first step to perform asteroseismolgy of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of δ Scuti stars. We select a sample of 15 δ Scuti stars observed by the CoRoT satellite, for which ultra-high quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of δ Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and ARMA interpolated data. The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. therefore, in order to reduce the effect of the spectral window to the minimum it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content, and not only to perform a pre-whitening of the data.

astro-ph.SR↗

arXiv2017

Statistical-likelihood Exo-Planetary Habitability Index (SEPHI)

A new Statistical-likelihood Exo-Planetary Habitability Index (SEPHI) is presented. It has been developed to cover the current and future features required for a classification scheme disentangling whether any discovered exoplanet is potentially habitable compared with life on Earth. The SEPHI uses likelihood functions to estimate the habitability potential. It is defined as the geometric mean of four sub-indexes related with four comparison criteria: Is the planet telluric?; Does it have an atmosphere dense enough and a gravity compatible with life?; Does it have liquid water on its surface?; Does it have a magnetic field shielding its surface from harmful radiation and stellar winds?. Only with seven physical characteristics, can the SEPHI be estimated: Planetary mass, radius, and orbital period; stellar mass, radius, and effective temperature; planetary system age. We have applied the SEPHI to all the planets in the Exoplanet Encyclopaedia using a Monte Carlo Method. Kepler-1229 b, Kepler-186 f, and Kepler-442 b have the largest SEPHI values assuming certain physical descriptions. Kepler-1229 b is the most unexpected planet in this privileged position since no previous study pointed to this planet as a potentially interesting and habitable one. In addition, most of the tidally locked Earth-like planets present a weak magnetic field, incompatible with habitability potential. We must stress that our results are linked to the physics used in this study. Any change in the physics used only implies an updating of the likelihood functions. We have developed a web application allowing the on-line estimation of the SEPHI: http://sephi.azurewebsites.net/

astro-ph.EP↗

arXiv2017

Precise surface gravities of $δ$ Scuti stars from asteroseismology

The work reported here demonstrates that it is possible to accurately determine surface gravities of $δ$ Sct stars using the frequency content from high precision photometry and a measurement of the parallax. Using a sample of 10 eclipsing binary systems with a $δ$ Sct component and the unique $δ$ Sct star discovered with a transiting planet, WASP-33, we were able to refine the $Δν-\barρ$ relation. Using this relation and parallaxes, we obtained independent values for the masses and radii, allowing us to calculate the surface gravities without any constraints from spectroscopic or binary analysis. A remarkably good agreement was found between our results and those published, extracted from the analysis of the radial velocities and light curves of the systems. This reinforces the potential of $Δν$ as a valuable observable for $δ$ Sct stars and settles the degeneracy problem for the $\log g$ determination through spectroscopy.

astro-ph.SR↗