Search Publications
Tests of stellar model atmospheres by optical interferometry. III. NPOI and VINCI interferometry of the M0 giant γ Sagittae covering 0.5-2.2 µm
Wittkowski, M.; Hummel, C. A.; Roccatagliata, V. +1 more
Context: .Optical interferometry allows a measurement of the intensity profile across a stellar disc, leading to a direct test and calibration of theoretical model atmospheres as well as to a precise determination of fundamental stellar parameters.
Aims: .We present a comparison of the visual and near-infrared intensity profile of the M0 giant…
Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy
Solanki, S. K.; Raouafi, N. -E.
The effect of the electron density stratification on the intensity profiles of the H I Ly-α line and the O VI and Mg X doublets formed in solar coronal holes is investigated. We employ an analytical 2-D model of the large scale coronal magnetic field that provides a good representation of the corona at the minimum of solar activity. We use the mas…
Spectral line width decrease in the solar corona: resonant energy conversion from Alfvén to acoustic waves
Oliver, R.; Zaqarashvili, T. V.; Ballester, J. L.
Context: .Observations reveal an increase with height of the line width of several coronal spectral lines probably caused by outwardly propagating Alfvén waves. However, the spectral line width sometimes shows a sudden decrease at a height ~0.1-0.2 R⊙, where the ratio of sound to Alfvén speeds may approach unity.
Aims: .To explain t…
Study of an extended EUV filament using SoHO/SUMER observations of the hydrogen Lyman lines
Heinzel, P.; Anzer, U.; Schmieder, B. +1 more
Context: .In previous work we determined the 3D structure of an EUV extension of the filament observed by SoHO/CDS on 15 October 1999. The determination of the 3D structure depends on the optical thickness τ912 at the hydrogen Lyman-continuum edge at 912 Å. The τ912 value was unknown, therefore it was taken as a free paramete…
The faint 2005 hard state outburst of Aquila X-1 seen by INTEGRAL and RXTE
Rodriguez, J.; Corbel, S.; Shaw, S. E.
We report on the spectral analysis of RXTE and INTEGRAL data of the 2005 April outburst of the transient Atoll source Aql X-1. Although this outburst is one of the faintest ever detected for this source in the soft X-rays (RXTE/ASM), one of our INTEGRAL observations, taken close to the soft X-ray peak, shows that the source flux was quite high, wi…
Coronal emission from the shocked circumstellar ring of SN 1987A
Lundqvist, P.; Spyromilio, J.; Gröningsson, P. +5 more
High resolution spectra with UVES/VLT of SN 1987A from December 2000 until November 2005 show a number of high ionization lines from gas with velocities of ± 350 km s-1, emerging from the shocked gas formed by the ejecta-ring collision. These include coronal lines from [Fe X], [Fe XI] and [Fe XIV] which have increased by a factor of 20 …
Interplanetary Lyman α line profiles: variations with solar activity cycle
Schmidt, W.; Bertaux, J. -L.; Lallement, R. +4 more
Aims.Interplanetary Lyman α line profiles are derived from the SWAN H cell data measurements. The measurements cover a 6-year period from solar minimum (1996) to after the solar maximum of 2001. This allows us to study the variations of the line profiles with solar activity.
Methods: .These line profiles were used to derive line shifts and lin…
Shock-cloud interaction in the Vela SNR. II. Hydrodynamic model
Miceli, M.; Bocchino, F.; Orlando, S. +1 more
Context: .In the framework of the study of the X-ray and optical emission in supernova remnants we focus on an isolated X-ray knot in the northern rim of the Vela SNR (Vela FilD), whose X-ray emission has been studied and discussed in Paper I.
Aims: .We aim at understanding the physical origin of the X-ray and optical emission in FilD, at unde…
Oxygen-rich disk in the V778 Cygni system resolved
Szczerba, R.; Richards, A. M. S.; Poutanen, J. +3 more
Aims.Various scenarios have been proposed to explain the presence of silicate features associated with carbon stars, such as
Methods: .The 22 GHz water maser emission from this star has been mapped using MERLIN wit…
Interstellar abundances in the neutral and ionized gas of NGC 604
Kunth, D.; Lebouteiller, V.; Vidal-Madjar, A. +5 more
Aims.We present FUSE spectra of the giant H ii region NGC 604 in the spiral galaxy M 33. Chemical abundances are tentatively derived from far-UV absorption lines and compared to those derived from optical emission lines.
Methods: .Absorption lines from neutral hydrogen and heavy elements were observed against the continuum provided by the youn…