Pole orientation of asteroid 44 Nysa via photometric astrometry,including a discussion of the method's application and its limitations     

R.C. Taylor  Edward F. Tedesco 《Icarus》1983,54(1):13-22

The results of photometric astrometry, a method of determining the orientation of a rotation axis, as applied to asteroid 44 Nysa are presented. The pole orientation of Nysa was found to be λ₀ = 100°, β₀ = +60° with an uncertainty of 10°. The sidereal period is 0^d.26755902 ± 0.00000006, and the rotation prograde. Refinements to, and limitations of, the application of the method of photometric astrometry are discussed. In light of the results presented herein, we believe that all photometric astrometry pole determinations of the past should be redone.  相似文献   

The diameter and albedo of 1943 Anteros     

G.J. Veeder  E.F. Tedesco  D.J. Tholen  A. Tokunaga  G. Kowal  K. Matthews  G. Neugebauer  B.T. Soifer 《Icarus》1981,46(2):281-284

We report the results of broadband visual and infrared photometry of the Apollo-Amor asteroid 1943 Anteros during its 1980 apparition. By means of a radiometric model, we calculate a diameter of 2.3 ± 0.2 km and a visual geometric albedo of 0.13 ± 0.03. The albedo and reflectance spectrum of Anteros imply that it is a type S asteroid. Thus, Anteros may have a silicate surface similar to other Apollo-Amor asteroids as well as some stony-iron meteorites.  相似文献   

The magmatic- and hydrothermal-dominated fumarolic system at the Active Crater of Lascar volcano,northern Chile     

F. Tassi  F. Aguilera  O. Vaselli  E. Medina  D. Tedesco  A. Delgado Huertas  R. Poreda  S. Kojima 《Bulletin of Volcanology》2009,71(2):171-183

Low-to-high temperature fumaroles discharging from the Active Crater of Lascar volcano (northern Chile) have been collected in November 2002, May 2005 and October 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic-hydrothermal system of this active volcano. Chemical and isotopic gas composition shows direct addition of high-temperature fluids from magmatic degassing, mainly testified by the very high contents of SO₂, HCl and HF (up to 87,800, 29,500 and 2,900 μmol/mol) and the high R/Ra values (up to 7.29). Contributions from a hydrothermal source, mainly in gas discharges of the Active Crater rim, has also been detected. Significant variations in fluid chemistry, mainly consisting of a general decrease of magmatic-related compounds, i.e. SO₂, have affected the fumarolic system during the period of observation, indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids. The chemical composition of Active Crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of Lascar volcano to be utilized in volcanic surveillance.  相似文献   

Geolithological and anthropogenic controls on the hydrochemistry of the Volturno river (Southern Italy)   总被引：1，自引：0，他引：1       下载免费PDF全文

Emilio Cuoco  Nicolò Colombani  Thomas H. Darrah  Micòl Mastrocicco  Dario Tedesco 《水文研究》2017,31(3):627-638

The present work aims to study the main chemical and physical water parameters in the upper and middle Volturno river catchment (southern Italy), between the Capo Volturno springs and the confluence with the Calore river. This study makes use of morphology, geolithology, tectonic, land use, and physico‐chemical (pH, electrical conductivity, redox potential, temperature, major ions, and ²²²Rn) data for the identification of the main sources of surface and groundwaters in the Volturno catchment and of their evolution and mixing both in base flow and peak flow conditions. The study was also performed to assess whether the alteration due to potential anthropogenic contamination may hamper the identification of natural “primitive” sources of surface waters, especially in the populated and farmed plains far from the river headwaters. Our data suggest that water chemistry of this stretch of the Volturno river is dominated mainly by lithology and, only marginally, by the intense exogenous activities and that this trend is appreciable in both base flow and peak flow conditions. The proposed simple geochemical approach based on easy‐to‐sample matrices and on cost‐effective standard methods is a valuable tool to address catchment functionality especially in upland areas, where complex geologic and structural settings, heterogeneous groundwater flow, and logistical issues are the rule rather than the exception. Because the upper and middle Volturno catchment is comparable with numerous valleys of the Mediterranean area, this study could be a reference for analogous applications.  相似文献   

Asteroid photometric and polarimetric phase curves: Joint linear‐exponential modeling     

K. Muinonen  A. Penttilä  A. Cellino  I. N. Belskaya  M. Delbò  A. C. Levasseur‐Regourd  E. F. Tedesco 《Meteoritics & planetary science》2009,44(12):1937-1946

Abstract— We present Markov‐Chain Monte‐Carlo methods (MCMC) for the derivation of empirical model parameters for photometric and polarimetric phase curves of asteroids. Here we model the two phase curves jointly at phase angles ≤25° using a linear‐exponential model, accounting for the opposition effect in disk‐integrated brightness and the negative branch in the degree of linear polarization. We apply the MCMC methods to V‐band phase curves of asteroids 419 Aurelia (taxonomic class F), 24 Themis (C), 1 Ceres (G), 20 Massalia (S), 55 Pandora (M), and 64 Angelina (E). We show that the photometric and polarimetric phase curves can be described using a common nonlinear parameter for the angular widths of the opposition effect and negative‐polarization branch, thus supporting the hypothesis of common physical mechanisms being responsible for the phenomena. Furthermore, incorporating polarimetric observations removes the indeterminacy of the opposition effect for 1 Ceres. We unveil a trend in the interrelation between the enhancement factor of the opposition effect and the angular width: the enhancement factor decreases with decreasing angular width. The minimum polarization and the polarimetric slope at the inversion angle show systematic trends when plotted against the angular width and the normalized photometric slope parameter. Our new approach allows improved analyses of possible similarities and differences among asteroidal surfaces.  相似文献   

Artificial macrophytes as fish habitat in a Mediterranean reservoir subjected to seasonal water level disturbances     

Luciano N. Santos  Angelo A. Agostinho  Carles Alcaraz  Joaquim Carol  Alejandra F. G. N. Santos  Pablo Tedesco  Emili García-Berthou 《Aquatic Sciences - Research Across Boundaries》2011,73(1):43-52

Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.  相似文献   

Asteroid polarimetric observations using the Torino UBVRI photopolarimeter     

A. Cellino  R. Gil Hutton  Ph. Bendjoya  E.F. Tedesco 《Icarus》2005,179(2):304-324

A long-term project of polarimetric observations of minor planets has been carried out since 1995 at the 2.15-m telescope of the El Leoncito Observatory (San Juan, Argentina) using the Torino photopolarimeter. We present here an updated summary of the results, including many measurements obtained during the most recent observing runs. The main purpose of the observations has been to obtain albedo estimates and compare them with previous IRAS radiometric determinations, mainly for objects having small (<50 km) IRAS diameters. Another field of investigation is the measurement of the degree of linear polarization at very small phase angles (less than 1°). The latter observations can be a useful input for modern theoretical models of light scattering from asteroid surfaces. In general, we have obtained a wealth of new results, including objects exhibiting a peculiar polarimetric behavior.  相似文献   

The eight-color asteroid survey: Results for 589 minor planets     

B. Zellner  D.J. Tholen  E.F. Tedesco 《Icarus》1985,61(3):355-416

Results are presented from reflection spectrophotometry of 589 minor planets in a photometric system using eight filter passbands ranging from 0.34- to 1.04-μm wavelength. The sampling completeness approaches or exceeds 50% of the numbered asteroids for the near-Earth objects, the Hungarias, the Nysa family, the Cybeles, the Hildas, and the Trojans. The general evolution of predominant compositional type from S to C to D with increasing heliocentric distance is evident, as is the spectral homogeneity of the Eos, Koronis, Nysa, and Themis families.  相似文献   

A geometrical method for quantifying endmembers' fractions in three-component groundwater mixing     

Emilio Cuoco  Stefano Viaroli  Thomas H. Darrah  Vittorio Paolucci  Roberto Mazza  Dario Tedesco 《水文研究》2021,35(11):e14409

We present a new geometrical method capable of quantifying and illustrating the outcomes of a three-component mixing dynamics. In a three-component mixing scenario, classical algebraic equations and endmember mixing analysis (EMMA) can be used to quantify the contributions from each fraction. Three-component mixing of natural waters, either in an element–element plot or by using the EMMA mixing subspace is described by a triangular shaped distribution of sample points where each endmember is placed on an apex, while each side corresponds to the mixing function of the two endmembers placed at the apex, considering the third endmembers' contribution equal to zero. Along each side, the theoretical mixing fractions can be computed using mass balance equations. Samples with contributions from three endmembers will plot inside the triangle, while the homogeneous barycentric coordinate projections can be projected onto the three sides. The geochemistry observed in the mineralized Ferrarelle aquifer system (southern Italy) results from three-component mixing of groundwater, each with diagnostic geochemical compositions. The defined boundary conditions allow us to parameterize and validate the procedures for modelling mixing, including selection of suitable geochemical tracers.  相似文献   

Triaxial equilibrium ellipsoids among the asteroids?     

P. Farinella  P. Paolicchi  E.F. Tedesco  V. Zappalà 《Icarus》1981,46(1):114-123

We present a physical model to explain the existence of a class of large-lightcurve-amplitude, rapidly rotating asteroids found most commonly among objects in the size range 100–300 km diameter. A significant correlation between rotation period and lightcurve amplitude exists for asteroids in this size range in the sense that those with larger amplitudes spin more rapidly and hence these objects have high rotational angular momenta. Since this is a property of Jacobi ellipsoids, we have investigated whether these asteriods might be examples of triaxial equilibrium ellipsoids. We find that objects rotating with periods of 6 hr must have densities between 1.1 and 1.4 g cm^?3, while those rotating in 4 hr would have densities between 2.4 and 3.2 g cm^?3. If this model is valid then at least some of these asteroids have rather low mean densities. The reality of this result and its interpretation in terms of collisional evolution of the asteroids is discussed.  相似文献