Search results for "Astrofisica"
showing 10 items of 481 documents
Mass accretion to young stars triggered by flaring activity in circumstellar discs
2011
Young low-mass stars are characterized by ejection of collimated outflows and by circumstellar discs which they interact with through accretion of mass. The accretion builds up the star to its final mass and is also believed to power the mass outflows, which may in turn remove the excess angular momentum from the star-disc system. However, although the process of mass accretion is a critical aspect of star formation, some of its mechanisms are still to be fully understood. A point not considered to date and relevant for the accretion process is the evidence of very energetic and frequent flaring events in these stars. Flares may easily perturb the stability of the discs, thus influencing th…
HADES RV programme with HARPS-N at TNG: XII. The abundance signature of M dwarf stars with planets
2020
[Context] Most of our current knowledge on planet formation is still based on the analysis of main sequence, solar-type stars. Conversely, detailed chemical studies of large samples of M dwarfs hosting planets are still missing.
Mitigation of the impact of stellar activity on observations of transiting planets
2023
La tesi si concentra sulla quantificazione dell'impatto dell'attività stellare sulle osservazioni dei pianeti in transito e sull'identificazione di una metodologia per correggere questi effetti. In particolare, viene approfondito l'effetto delle macchie stellari, sia non occultate che occulte. La presenza di macchie sul disco stellare visibile può distorcere la curva della luce di transito primaria in modo dipendente dalla lunghezza d'onda, mimando la presenza di un'atmosfera. Per tener conto di questo effetto, la tesi presenta un metodo innovativo per stimare le proprietà delle macchie e la loro distribuzione dalle osservazioni fuori transito e, su questa base, correggere le curve di luce …
Search for intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network
2019
Gravitational wave astronomy has been firmly established with the detection of gravitational waves from the merger of ten stellar mass binary black holes and a neutron star binary. This paper reports on the all-sky search for gravitational waves from intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network. The search uses three independent algorithms: two based on matched filtering of the data with waveform templates of gravitational wave signals from compact binaries, and a third, model-independent algorithm that employs no signal model for the incoming signal. No intermediate mass black hole binary event was detected in this sear…
Deep ROSAT-HRI observation of the cD galaxy NGC 1399 in the fornax cluster: Morphology and dynamical status of the X-ray halo
2002
We present the results of a deep (167 ks) observation of the NGC 1399/NGC 1404 field obtained from data collected between 1993 and 1996 with the ROSAT High Resolution Imager. We take advantage of the 5" resolution of the HRI to study in detail the structure of the galactic halo and to relate the results to those obtained at larger scales with poorer resolution instruments. We discuss possible non-equilibrium scenarios that may explain the global halo structure. We also find evidence of interactions between the nuclear radio source and the inner gaseous halo.
Observatory science with eXTP
2019
Disponible preprint en: arXiv:1812.04023v1 [astro-ph.HE] [v1] Mon, 10 Dec 2018 19:00:52 UTC (4,376 KB)
Filters design and characterization for LAD instrument onboard eXTP
2022
Copyright 2022 Society of Photo‑Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, and modification of the contents of the publication are prohibited. The LAD (Large Area Detector) instrument, onboard the Sino-European mission eXTP (enhanced X-ray Timing and Polarimetry), will perform single-photon, high-resolution timing and energy measurements, in the energy range 2–30 keV, with a large collecting area. Its silicon drift detectors need shielding from NIR/Vis/UV light by astrophysical sources and the bright Ea…
Searching for differences in Swift's intermediate GRBs
2010
Gamma-ray bursts are usually classified through their high-energy emission into short-duration and long-duration bursts, which presumably reflect two different types of progenitors. However, it has been shown on statistical grounds that a third, intermediate population is needed in this classification scheme, although an extensive study of the properties of this class has so far not been done. The large amount of follow-up studies generated during the Swift era allows us to have a suficient sample to attempt a study of this third population through the properties of their prompt emission and their afterglows. Our study is focused on a sample of GRBs observed by Swift during its first four y…
Euclid preparation. XII. Optimizing the photometric sample of the Euclid survey for galaxy clustering and galaxy-galaxy lensing analyses
2021
Pocino, A., et al. (Euclid Collaboration)
Population Properties of Compact Objects from the Second LIGO-Virgo Gravitational-Wave Transient Catalog
2021
Abbott, R., et al. (LIGO and Virgo Collaboration)