Search Publications
Interstellar CO towards X Persei (HD 24534) - I. One-component model
Kaczmarczyk, Grzegorz
Data on molecular CO in absorbing gas towards X Per, from the International Ultraviolet Explorer (IUE) and the echelle mode of the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope, are reported. A statistical equilibrium model is used to recreate equivalent widths of CO bands and reproduce high-resolution GHRS spectra.…
The Velocity Field of Young Stars in the Solar Neighbourhood
Comerón, F.; Figueras, F.; Torra, J. +1 more
A sample of O- and B-type stars with Hipparcos astrometric data, ages computed from Strömgren photometry and radial velocities, has been used to characterize the structure, age and kinematics of the Gould Belt system. The local spiral structure of our galaxy is determined from this sample, and also from a sample of Hipparcos Cepheid stars. The Gou…
The Influence of Fluctuations of the Solar Emission Line Profileon the Doppler Shift of Interplanetary HLyα Lines Observed by the Hubble–Space–Telescope
Scherer, H.; Fahr, H. J.; Bzowski, M. +1 more
In an earlier research the employment of a radiation transport model with angle-dependent partial frequency redistribution, self-absorption by interplanetary hydrogen, realistic solar HLyαemission profile, and a time dependent `hot' hydrogen model to analyze 5 interplanetary HLyα glow spectra obtained with theHubble–Space–Tel…
17 µm imaging of eta Carinaea: an onion-like structure for the lobes?
Pantin, E.; Le Mignant, D.
We have obtained a 17 mu m image of the eta Carinae nebula with a signal to noise ratio never reached before. Once deconvolved, the spatial resolution is of the order of 0.5\arcsec. The ring and arclike structures seen at 17 mu m are very similar to those observed at 12.5 mu m; however the intensity maximum is located elsewhere in a dense cold str…
Influence of Turbulent Energy Spectra on Damping and Frequency Reduction of the Solar F-Mode
Murawski, K.; Mędrek, M.
This paper generalizes the random wave theory that was developed to explain the recently observed line width spreading and frequency reduction of the f-mode. The generalization is based on a replacement of the Gaussian energy spectrum by a more realistic spectrum such as von Karman, Reynolds, or exponential as well as on an averaging of the result…
Line-profile variation in tau Herculis
Masuda, Seiji; Hirata, Ryuko
Based on a time series of high-resolution spectra at He I lambda 4471 and Mg Ii lambda 4481, we have detected the line-profile variation of
Preconditioning the Differential Emission Measure (Te) Inverse Problem
Brown, J. C.; Charbonneau, P.; McIntosh, S. W.
In an inverse problem of any kind, poor conditioning of the inverse operator decreases the numerical stability of any unregularized solution in the presence of data noise. In this paper we show that the numerical stability of the differential emission measure (DEM) inverse problem can be considerably improved by judicious choice of the integral op…
Trapping and Precipitation of Protons during Stochastic Acceleration in Magnetic Loops
Torsti, J.; Kocharov, L.; Kovaltsov, G. A.
We study confinement of particles during the stochastic acceleration in coronal magnetic loops. Analytic solutions and Monte Carlo simulations of the coordinate-dependent focused-diffusion transport and acceleration are employed to deduce the effective leaky-box escape time, τesc. The rigorously correct expression of the escape time yie…
ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997
Anttila, A.; Sahla, T.
Two Earth-directed coronal mass ejections (CMEs), which were most effective in energetic (~1-50 MeV) particle acceleration during the first 18 months since the Solar and Heliospheric Observatory (SOHO) launch, occurred on April 7 and May 12, 1997. In the analysis of these events we have deconvoluted the injection spectrum of energetic protons by u…
The UV (IUE) spectrum of the planetary nebula PC 11 (HD 149427)
Pottasch, S. R.; de Martino, D.; García-Lario, P. +2 more
The UV spectrum of PC 11 is found to show variations in the strength of the O III] 1666Ä , N III] 1750Ä and C III] 1909Ä emission lines. The detection of continuum emission in the wavelength interval 2650Ä to 3200Ä indicates that the central star of PC 11 has an early F-type dwarf companion. The very low level of UV continuum in the wavelength int…