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By means of a new homogeneous set of data from 34 double-lined detached systems, we have recalibrated the colour-surface brightness correlation in the interval –0.3(B-V)o0.95. A comparison is made with Wesselink's calibration. We find that Wesselink's method can provide a good estimate of the stellar radii. 相似文献
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Italo Foppiani John M. Hill Matteo Lombini Giovanni Bregoli Giuseppe Cosentino Emiliano Diolaiti Thomas M. Herbst Giancarlo Innocenti Daniel Meschke Douglas L. Miller Ralf-Rainer Rohloff Laura Schreiber 《Experimental Astronomy》2011,31(2-3):115-130
We describe the design, integration, and operation of the infrared test cameras for the commissioning of the Large Binocular Telescope. The design and construction phase lasted slightly more than one year from February 2007 to April 2008 and was the result of a joint collaboration among INAF Osservatorio Astronomico di Bologna, Università di Bologna Dipartimento di Astronomia (Italy) and the Max-Planck-Institut für Astronomie (Heidelberg, Germany). Thereafter, the camera was delivered to the LBT Observatory (USA) for commissioning of the telescope active optics and, more recently, for commissioning of the first light adaptive optics. 相似文献
3.
Following the line of research outlined by Strittmatter and Wickramasinghe (1971) and recently by Shipman (1972), attention was drawn to the study of convective zones in white dwarfs for various masses and chemical compositions, in order to understand some observational features of their spectra. According to the results, convection strongly depends on the mass of the star, forM<0.5 M⊙, and low hydrogen abundancesX?0.2) are sufficient to decrease the extension of the He-convection zones with respect to pure-He models. It is shown that the existence of DB white dwarfs seems not in agreement with the accretion rates predicted by Bondi (1952), and that DB's must evolve into H-lacking white dwarfs. 相似文献
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Angelo Gavezzotti Francesco Demartin Carlo Castellano Italo Campostrini 《Physics and Chemistry of Minerals》2013,40(2):175-182
An accurate structure refinement, using single-crystal X-ray diffraction data, on natural α- and β-dimorphites collected at Solfatara di Pozzuoli, in the Phlegraean Fields, near Naples and at Vesuvius (Italy) is reported. Theoretical calculations at various levels of sophistication have been used to calculate molecular vibrational frequencies and gas-phase specific heats, to analyze the crystal packing, and to estimate lattice energies of both phases. All computational methods contribute to demonstrate that the β-phase is the thermodynamically stable one at room temperature. 相似文献
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L. Schreiber I. Foppiani C. Robert E. Diolaiti J.-M. Conan M. Lombini 《Monthly notices of the Royal Astronomical Society》2009,396(3):1513-1521
Over the last few years increasing consideration has been given to the study of laser guide stars (LGS) for the measurement of the disturbance introduced by the atmosphere in optical and near-infrared (near-IR) astronomical observations from the ground. A possible method for the generation of a LGS is the excitation of the sodium layer in the upper atmosphere at approximately 90 km of altitude. Since the sodium layer is approximately 10 km thick, the artificial reference source looks elongated, especially when observed from the edge of a large aperture. The spot elongation strongly limits the performance of the most common wavefront sensors. The centroiding accuracy in a Shack–Hartmann wavefront sensor, for instance, decreases proportionally to the elongation (in a photon noise dominated regime). To compensate for this effect, a straightforward solution is to increase the laser power, i.e. to increase the number of detected photons per subaperture. The scope of the work presented in this paper is twofold: an analysis of the performance of the weighted centre of gravity algorithm for centroiding with elongated spots and the determination of the required number of photons to achieve a certain average wavefront error over the telescope aperture. 相似文献
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Italo Mazzitelli 《Astrophysics and Space Science》1972,17(2):378-389
The luminosity function derived for main sequence stars in the neighbourhood of the Sun shows evidence for a flattening in
the interval 5≲M
v
≲8. An interpretation of this feature by means of theoretical models enables us to deduce the mass function for stars belonging
to the main sequence.
Sommario Viene ricavata la funzione di luminosità per stelle di sequenza principale vicine al Sole. Si evidenzia un pianerottolo per 5≲M v ≲8. II confronto con i modelli teorici consente di desumere la funzione di massa della sequenza principale.相似文献
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Francesco Demartin Italo Campostrini Carlo Castellano Massimo Russo 《Physics and Chemistry of Minerals》2014,41(6):403-407
The new mineral parascandolaite, isotypic to cubic perovskites, space group Pm \(\overline{3}\) m (no. 221) is the natural analog of the synthetic fluoride KMgF3 and is related to neighborite, NaMgF3. It was found as a volcanic sublimate at Vesuvius volcano on 1944 eruption lava scoria, associated with opal, cerussite, mimetite, phoenicochroite and coulsellite. It occurs as transparent colorless to white cubic crystals up to 0.5 mm in length with vitreous luster. The density measured by flotation in a diiodomethane–toluene mixture is 3.11(1) g/cm3; that calculated from the empirical formula and single-crystal X-ray data is 3.123 g/cm3. The mineral is isotropic with n = 1.395(5) (580 nm). The six strongest reflections in the X-ray powder diffraction pattern are: [d obs in Å(I)(h k l)] 2.001(100)(2 0 0), 2.831(83)(1 1 0), 2.311(78)(1 1 1), 1.415(56)(2 2 0), 1.633(35)(2 1 1) and 1.206(22)(3 1 1). The unit-cell parameter is a = 4.0032(9) Å. The structure was refined to a final R(F) = 0.0149 for 35 independent observed reflections [I > 2σ(I)]. The mineral is named after the Italian mineralogist Antonio Parascandola (1902–1977). 相似文献
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J-Hook vanes are grade control structures used to stabilize the riverbed. This paper aims to investigate the behaviour of J-Hook vanes as a grade-control structure in straight rivers. Scour downstream of J-Hook vane structures like other grade-control structures depends on the shape of the structure and the river hydraulic conditions. The purpose of this study is classifying the scour geometry and predicting the main scour parameters such as the scour depth, length, width, and the ridge height and length downstream of the J-Hook vanes in straight rivers. Experiments were carried out in a horizontal channel. For each length of the structure, three heights in different hydraulic conditions, including densimetric Froude numbers, water drops, and opening ratios, were tested. Results show that the densimetric Froude number, the drop height, and the height of the structure are the key parameters to form and classify the scour. Equations have been derived using dimensional analysis and experimental data to predict the maximum scour depth, the maximum length of the scour, the maximum scour width, and the maximum height and length of the dune. All the experiments were conducted in clear water conditions. 相似文献
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Adolfo Panarello Maria Rita Palombo Italo Biddittu Mauro Antonio Di Vito Gennaro Farinaro Paolo Mietto 《第四纪科学杂志》2020,35(3):444-456
The Foresta ichnosite is well known for preserving some of the oldest human fossil footprints recorded in Europe so far. This research aims to: i) describe new footprints that are larger than those already reported, some of which form a new trackway that moves in the opposite direction to all the others; ii) announce the discovery of some stone tools also in the surroundings of the Foresta ichnosite. The new results increase the total number of human fossil footprints to at least 81, specify the direction and the number of footprints of Trackway C, and identify three new directions of walking at the site. More compelling and complete estimates of the dimensional range of all ichnological evidence enables us, furthermore, to estimate the number of trackmakers walking on the trampled surface as a minimum of five, one of them likely being an adult male. The general shape of all the recorded footprints suggests that the Foresta trackmakers share some similarities with those at Sima de los Huesos, and belong to the same taxonomical group as the Ceprano skull. All the new evidence enables us to better understand the presence of hominin populations in the Roccamonfina volcano area during the Middle Pleistocene. © 2020 John Wiley & Sons, Ltd. 相似文献
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