Stellar surface rotation carries information about stellar parameters-particularly ages-and thus the large rotational data sets extracted from Kepler time series represent powerful probes of stellar ...populations. In this article, we address the challenge of interpreting such data sets with a forward-modeling exercise. We combine theoretical models of stellar rotation, a stellar population model for the galaxy, and prescriptions for observational bias to predict the rotation distribution in the Kepler field under standard "vanilla" assumptions. We arrive at two central conclusions: first, that standard braking models fail to reproduce the observed distribution at long periods, and second, that the interpretation of the period distribution is complicated by a mixture of evolutionary states and observational uncertainties. If we assume that the detectability of rotational signatures scales with the Rossby number, we can show that the observed period distribution contains an apparent "Rossby edge" at , above which long-period, high Rossby number stars are either absent or undetected. This threshold suggests either that weakened magnetic braking is in operation in the full Kepler population or that stars undergo a transition in spottedness and activity. We discuss the observations necessary to disentangle these competing scenarios. Regardless of the physical origin of the edge, it biases the inferred age distributions, affecting stars older than ∼9 Gyr at , older than at solar temperatures, and at 6500 K. Below , rotation periods should be viable age diagnostics in even the oldest stars in the population.
We report the discovery of TOI-677b,first identified as a candidate in light curves obtained within Sectors 9 and 10 of the Transiting Exoplanet Survey Satellite(TESS)mission and confirmed with ...radial velocities. TOI-677b has a mass of M(p) = 1.236(+0.069,- 0.067) M(J), a radius of R(P)=1.170 ± 0.03 R(J), and orbits its bright host star (V = 9.8 mag) with an orbital period of 11.23660 ± 0.00011 d, on an eccentric orbit with e = 0.435 ± 0.024. The host star has a mass of M(*) = 1.181 ± 0.058 M(ʘ), a radius of R(*)= 1.28(+0.03,-0.03) R(ʘ), an age of 2.92 (+0.80,-0.73) Gyr and solar metallicity, properties consistent with a main-sequence late-F star with T(eff)=6295 ± 77K. We find evidence in the radial velocity measurements of a secondary long-term signal, which could be due to an outer companion. The TOI-677 b system is a well-suited target for Rossiter–Mclaughlin observations that can constrain migration mechanisms of close-in giant planets.
Dataset of annual monitoring of herbivory effects on the conservation status of the endangered species Androcymbium europaeum (Lange) K. Richt and its associated plant communities is presented in ...this manuscript. This dataset encompasses the annual monitoring of herbivory effects on the conservation status of the endangered species Androcymbium europaeum . Since 2010, the SERPAM Department (Service of Evaluation, Restoration and Protection of Mediterranean Agrosystems) at the Zaidin Experimental Station, belonging to the Spanish National Research Council (CSIC-EEZ), has conducted annual sampling to assess the impact of both domestic and wild livestock, specifically rabbits, on the pastures where A. europaeum lives. The study consisted of a randomised block design, implementing three distinct treatments to evaluate different management strategies: (1) rabbit and domestic herbivory, (2) exclusion of domestic livestock and (3) exclusion of rabbits and domestic livestock. Within each treatment, two types of monitoring were conducted. Firstly, the abundance of A. europaeum was estimated by counting individuals within 50 cm x 50 cm quadrats. Secondly, plant species diversity was assessed along 2-m long transects using the modified Point-Quadrat method. The research was conducted within the Cabo de Gata-Níjar Natural Park in southern Spain, specifically in the Amoladeras Nature Reserve in Almería. The dataset contains information spanning from 2010 to 2023, providing valuable insights into the annual monitoring of herbivory effects on the conservation status of A. europaeum , contributing to our understanding of the species' interaction with domestic and wild animal in the studied area.
The use of drones for vegetation monitoring allows the acquisition of large amounts of high spatial resolution data in a simple and fast way. In this study, we evaluated the accuracy of vegetation ...cover estimation by drones in Mediterranean semi-arid shrublands (Sierra de Filabres; Almería; southern Spain) after prescribed burns (2 years). We compared drone-based vegetation cover estimates with those based on traditional vegetation sampling in ninety-six 1 m2 plots. We explored how this accuracy varies in different types of coverage (low-, moderate- and high-cover shrublands, and high-cover alfa grass steppe); as well as with diversity, plant richness, and topographic slope. The coverage estimated using a drone was strongly correlated with that obtained by vegetation sampling (R2 = 0.81). This estimate varied between cover classes, with the error rate being higher in low-cover shrublands, and lower in high-cover alfa grass steppe (normalized RMSE 33% vs. 9%). Diversity and slope did not affect the accuracy of the cover estimates, while errors were larger in plots with greater richness. These results suggest that in semi-arid environments, the drone might underestimate vegetation cover in low-cover shrublands.
Improving PARSEC models for very low mass stars Chen, Yang; Girardi, Léo; Bressan, Alessandro ...
Monthly notices of the Royal Astronomical Society,
11/2014, Letnik:
444, Številka:
3
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Many stellar models present difficulties in reproducing basic observational relations of very low mass stars (VLMS), including the mass-radius relation and the optical colour-magnitudes of cool ...dwarfs. Here, we improve parsec (PAdova-TRieste Stellar Evolution Code) models on these points. We implement the T- ... relations from phoenix BT-Settl model atmospheres as the outer boundary conditions in the parsec code, finding that this change alone reduces the discrepancy in the mass-radius relation from 8 to 5 per cent. We compare the models with multiband photometry of clusters Praesepe and M67, showing that the use of T- ... relations clearly improves the description of the optical colours and magnitudes. But anyway, using both Kurucz and phoenix model spectra, model colours are still systematically fainter and bluer than the observations. We then apply a shift to the above T- ... relations, increasing from 0 at Teff = 4730 K to ~14 per cent at Teff = 3160 K, to reproduce the observed mass-radius relation of dwarf stars. Taking this experiment as a calibration of the T- ... relations, we can reproduce the optical and near-infrared colour-magnitude diagrams of low-mass stars in the old metal-poor globular clusters NGC 6397 and 47 Tuc, and in the intermediate-age and young solar-metallicity open clusters M67 and Praesepe. Thus, we extend parsec models using this calibration, providing VLMS models more suitable for the lower main-sequence stars over a wide range of metallicities and wavelengths. Both sets of models are available on parsec webpage. (ProQuest: ... denotes formulae/symbols omitted.)
Dissecting the Gaia HR diagram within 200 pc Dal Tio, Piero; Mazzi, Alessandro; Girardi, Léo ...
Monthly notices of the Royal Astronomical Society,
10/2021, Letnik:
506, Številka:
4
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ABSTRACT
We analyse the high-quality Hertzsprung–Russell diagram (HRD) derived from Gaia data release 2 for the Solar Neighbourhood. We start building an almost complete sample within 200 pc and for ...|b| > 25○, so as to limit the impact of known errors and artefacts in the Gaia catalogue. Particular effort is then put into improving the modelling of population of binaries, which produce two marked features in the HRD: the sequence of near-equal mass binaries along the lower main sequence, and the isolated group of hot subdwarfs. We describe a new tool, BinaPSE, to follow the evolution of interacting binaries in a way that improves the consistency with PARSEC evolutionary tracks for single stars. BinaPSE is implemented into the TRILEGAL code for the generation of ‘partial models’ for both single and binary stellar populations, taking into account the presence of resolved and unresolved binaries. We then fit the Gaia HRD via Markov chain Monte Carlo methods that search for the star formation history and an initial binary fraction (by mass) that maximize the likelihood. The main results are (i) the binary fraction derived from the lower MS is close to 0.4, while twice larger values are favoured when the upper part of the HRD is fitted; (ii) present models predict the observed numbers of hot subdwarfs to within a factor of 2; and (iii) irrespective of the prescription for the binaries, the star formation rate peaks at values $\sim \!1.5\times 10^{-4}{\rm{M}_{\odot }}\mathrm{yr}^{-1}$ at ages slightly above 2 Gyr, and then decreases to $\sim \!0.8\times 10^{-4}{\rm{M}_{\odot }}\mathrm{yr}^{-1}$ at very old ages.
Stellar Spin-Orbit Misalignment in a Multiplanet System Huber, Daniel; Carter, Joshua A.; Barbieri, Mauro ...
Science (American Association for the Advancement of Science),
10/2013, Letnik:
342, Številka:
6156
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Stars hosting hot Jupiters are often observed to have high obliquities, whereas stars with multiple coplanar planets have been seen to have low obliquities. This has been interpreted as evidence that ...hot-Jupiter formation is linked to dynamical disruption, as opposed to planet migration through a protoplanetary disk. We used asteroseismology to measure a large obliquity for Kepler-56, a red giant star hosting two transiting coplanar planets. These observations show that spin-orbit misalignments are not confined to hot-Jupiter systems. Misalignments in a broader class of systems had been predicted as a consequence of torques from wide-orbiting companions, and indeed radial velocity measurements revealed a third companion in a wide orbit in the Kepler-56 system.
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