A semi-analytical model of stellar flares

We present a simplified point'' model to describe the hydrodynamic response of coronal loop plasma to the sudden release of energy which occurs at the time of a flare. Our simplification allows the full set of partial differential equations for energy, momentum, and mass conservation to be replaced by a corresponding set of ordinary differential equations for the plasma properties averaged over the loop volume. The temporal profiles of plasma temperature, density, and velocity are calculated over a time interval long enough to ensure that pre-flare conditions are re-established. The model is used for the interpretation of stellar flare data. In particular, we derive a set of representative loop geometries and flare energy inputs which allows us to reproduce the high emission measures typically inferred from observations of stellar flares. 4 refs., 1 fig

Near-infrared observations of galaxies in Pisces-Perseus: I. H-band surface photometry of 174 spirals

We present near-infrared, H-band (1.65 um), surface photometry of 174 spiral galaxies in the area of the Pisces-Perseus supercluster. The images, acquired with the ARNICA camera mounted on various telescopes, are used to derive radial profiles of surface brightness, ellipticities, and position angles, together with global parameters such as H-band magnitudes and diameters. The mean relation between H-band isophotal diameter D_{21.5} and the B-band D_{25} implies a B-H color of the outer disk bluer than 3.5; moreover, D_{21.5}/D_{25} depends on (global) color and absolute luminosity. The correlations among the various photometric parameters suggest a ratio between isophotal radius D_{21.5}/2 and disk scale length of about 3.5 and a mean disk central brightness of 17.5 H-mag arcsec^{-2}. We confirm the trend of the concentration index C_{31} with absolute luminosity and, to a lesser degree, with morphological type. We also assess the influence of non-axisymmetric structures on the radial profiles and on the derived parameters.Comment: 10 pages, 11 postscript figures (one table and one figure are available only at the CDS); to be published on A&A

Silicon in and out of grains

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Infrared instrumentation for large telescopes: an alternative approach

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

The importance of dust grains in astrochemistry

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

The fractional ionization in molecular cloud cores

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Diagnostic determination of ionization and density in stellar jets from line ratios

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

The evolution of pre-main-sequence stars

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Annual report 2002

Printed from http://www.arcetri.astro.it target=NewWindow>www.arcetri.astro.it (December 2004)Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Ionization and density along the beams of Herbig-Haro jets

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal