Search results for " serie"

ESO-Hα 574 and Par-Lup 3-4 jets: Exploring the spectral, kinematical, and physical properties

2014

In this paper a comprehensive analysis of VLT / X-Shooter observations of two jet systems, namely ESO-H$\alpha$ 574 a K8 classical T Tauri star and Par-Lup 3-4 a very low mass (0.13~\Msun) M5 star, is presented. Both stars are known to have near-edge on accretion disks. A summary of these first X-shooter observations of jets was given in a 2011 letter. The new results outlined here include flux tables of identified emission lines, information on the morphology, kinematics and physical conditions of both jets and, updated estimates of $\dot{M}_{out}$ / $\dot{M}_{acc}$. Asymmetries in the \eso flow are investigated while the \para jet is much more symmetric. The density, temperature, and ther…

Vibrational Energy Levels via Finite-Basis Calculations Using a Quasi-Analytic Form of the Kinetic Energy

2015

A variational method for the calculation of low-lying vibrational energy levels of molecules with small amplitude vibrations is presented. The approach is based on the Watson Hamiltonian in rectilinear normal coordinates and characterized by a quasi-analytic integration over the kinetic energy operator (KEO). The KEO beyond the harmonic approximation is represented by a Taylor series in terms of the rectilinear normal coordinates around the equilibrium configuration. This formulation of the KEO enables its extension to arbitrary order until numerical convergence is reached for those states describing small amplitude motions and suitably represented with a rectilinear system of coordinates. …

Be stars in open clusters. I. uvby $ ^{\bf \beta}$ photometry

1996

We present uvby β photometry for Be stars in eight open clusters and two OB associations. It is shown that Be stars occupy anomalous positions in the photometric diagrams, which can be explained in terms of the circumstellar continuum radiation contribution to the photometric indices. In the - M V plane Be stars appear redder than the non emission B stars, due to the additional reddening caused by the hydrogen free-bound and free-free recombination in the circumstellar envelope. In the c 0 - M V plane the earlier Be stars present lower c 0 values than absorption-line B stars, which is caused by emission in the Balmer discontinuity, while the later Be stars deviate towards higher c 0 values,…

A fast approximate method for the calculation of the infrared radiation balance within city street cavities

1983

The approximate calculation method for diffuse solar irradiances in street cavities presented in an earlier paper is extended to include infrared flux densities. By expanding the infrared sky radiance as a truncated trigonometric series, it becomes possible to solve the integrals representing the obstruction of the sky analytically. An example is worked out to demonstrate the numerically very efficient calculation procedure.

Entropy and Renormalization in Chaotic Visibility Graphs

2016

Simultaneous uvbyβ Photometry and Hα Spectroscopy of Be Stars in Open Clusters

1994

The usual methods of spectral clasification, equivalent widths of Balmer lines or photometric calibrations are not suitable for the determination of the astrophysical parameters of the underlying star in Be-type objects. The spectrum is distorted by the circumstellar envelope lines, while the contribution of the envelope continuum radiation contaminates the photometric indices.

Linear Methods in Nilpotent Groups

1982

The subject of this chapter is commutator calculation. It will be recalled that the commutator [x, y] of two elements x, y of a group is defined by the relation $$ [x,y] = {{x}^{{ - 1}}}{{y}^{{ - 1}}}xy. $$ . We then have $$ [xy,z] = {{[x,z]}^{y}}[y,z],\quad [x,yz] = [x,z]{{[x,y]}^{z}}. $$ . These relations are rather similar to the conditions for bilinearity of forms, and there are a number of ways of formalizing this similarity. Once this is done, commutator calculations can be done by linear methods. Several examples of theorems proved by this method will be given in this chapter.

Harmonic solution of semiconductor transport equations for microwave and millimetre-wave device modelling

2004

The transport equations for charges in a semiconductor have been solved for a periodic voltage excitation by means of a harmonic approach, for modelling of microwave and millimetre-wave active devices. The solution is based on the expansion of the unknown physical quantities in Fourier series in the time domain, and on the discretisation in the space domain. A Waveform-Balance technique in the time domain is used to solve the resulting non-linear equations system. In this way the time step is determined only by Nyquist's sampling requirements at the operating frequency, irrespective of the relaxation times of the semiconductor. This approach allows for a longer time step, and therefore a sh…

Comparison of hydrogen Balmer-alpha Stark profiles measured at high electron densities with theoretical results

2005

Profiles of the H-alpha line calculated using the full computer simulation method (FCSM) and the standard theory (ST) agree excellently with a measured profile (at an electron density of Ne = 9.0 × 1016 cm−3 and temperature T = 12 600 K) in an argon–hydrogen (minority) arc plasma. Calculated widths (FCSM) and shifts (ST) also agree well with experimental data from flash-tube plasmas and gas-linear pinch plasmas. Some discrepancies are probably caused by experimental flaws. Our analysis of the so-called generalized theory (GT) shows that this theory is burdened with un-physical approximations, and consequently so are all subsequent modifications based on GT. It is shown that the so-called ac…

Study of the far wing of the Balmer α line of hydrogen perturbed by collisions with protons

2002

The theory of the Balmer α line of atomic hydrogen perturbed by collisions with protons predicts quasi-molecular satellites in the line wing due to H-H+ collisions. Measurements of the spectrum of a laser-produced plasma confirm the existence of the strongest of these features.