Search results for "STELLAR"
showing 7 items of 1237 documents
Euclid preparation: XI. Mean redshift determination from galaxy redshift probabilities for cosmic shear tomography
2021
Ilbert, O., et al. (Euclid Collaboration)
A photometric study of Be stars located in the seismology fields of COROT
2007
Context: In preparation for the COROT mission, an exhaustive photometric study of Be stars located in the seismology fields of the COROT mission has been performed. The very precise and long-time-spanned photometric observations gathered by the COROT satellite will give important clues of the origin of the Be phenomenon. Aims: The aim of this work is to find short-period variable Be stars located in the seismology fields of COROT and to study and characterise their pulsational properties. Methods: Light curves obtained at the Observatorio de Sierra Nevada together with data from Hipparcos and ASAS-3 of a total of 84 Be stars have been analysed in order to search for short-term variations. W…
Weed vegetation of cereal crops in Tajikistan (Pamir Alai Mts., Middle Asia)
2013
The paper presents results of investigations of weed vegetation conducted in crop fields, in Tajikistan (Middle Asia) - one of the world cradles of the weed flora. The study has been based on 299 phytosociological relevés obtained in various geobotanical regions of the country in 2009-2012. In the examined vegetation patches 469 vascular plant species were noted. Many of the recorded species are widespread weeds. However, there were also some rare and endemics taxa (e.g. Prangos pabularia, P. saraw-schanica and Thlaspidium thlaspi) observed in the sample plots. The collected material presents probably, the majority of the variability among the weed communities of crop cultivations in the Mi…
Three-dimensional core-collapse supernovae with complex magnetic structures: I. Explosion dynamics
2021
Magnetic fields can play a major role in the dynamics of outstanding explosions associated to violent events such as GRBs and hypernovae, since they provide a natural mechanism to harness the rotational energy of the central proto-neutron star and power relativistic jets through the stellar progenitor. As the structure of such fields is quite uncertain, most numerical models of MHD-driven core-collapse supernovae consider an aligned dipole as initial magnetic field, while the field's morphology can actually be much more complex. We present three-dimensional simulations of core-collapse supernovae with more realistic magnetic structures, such as quadrupolar fields and, for the first time, an…
Estudio de pequeños elementos magnéticos en la fotosfera y cromosfera solar con telescopios en tierra y espaciales = Study of small magnetic elements…
2011
The photosphere is the best known layer of the Sun, as it delimits its surface and furthermore, it has been observed in detail since the beginning of the telescopic era. The convection zone redistributes the magnetic field over the photosphere and the upper layers. On the many scales of the solar surface magnetism, the smallest elements seen in the photosphere are the most unknown, due to the limit in resolution of a finite telescope. The structures that are smaller than typically 100 km are smeared out. In this Thesis, the small bright features of the magnetic network and internetwork over the resolution limit are analysed from the dynamical point of view, and linked with their physical pr…
Discovery of an Exceptionally Strong β -Decay Transition of $^{20}$F and Implications for the Fate of Intermediate-Mass Stars
2019
A significant fraction of stars between 7-11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on $^{20}$Ne in the degenerate oxygen-neon stellar core. However, due to the unknown strength of the transition between the ground states of $^{20}$Ne and $^{20}$F, it has not previously been possible to fully constrain the rate. By measuring the transition, we have established that its strength is exceptionally large and enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupted b…
Excess electronic recoil events in XENON1T
2020
We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 t-y and an unprecedentedly low background rate of $76\pm2$ events/(t y keV) between 1 and 30 keV, the data enables sensitive searches for solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4$\sigma$ significance, and a 3D 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by $g_{ae}<3.8 \times 10^{-12}$,…