Search Publications
Solar p-modes from 1979 days of the GOLF experiment
Grec, G.; Salabert, D.; Gelly, B. +5 more
With the GOLF instrument onboard the SoHO observatory, 1979 days of full-disc Doppler velocity observations have been compiled into a study of p-mode properties. We develop a multi-step iterative method (MSIM) algorithm to access all p-mode parameters while minimizing any perturbating effect or cross-talk between parameters during their determinat…
Resolving subdwarf B stars in binaries by HST imaging
Heber, U.; Green, E. M.; Thejll, P. +2 more
The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little success. We have carried out a small survey of spectroscopic binary candidates (19 systems consisting of an sdB star and late type companion) with the Plan…
The physical structure of Magellanic Cloud H II regions. II. Elemental abundances
van der Hulst, J. M.; Vermeij, R.
Based on a new data set of optical and infrared spectra described in Vermeij et al. (\cite{Ronald}), we analyse the gas-phase elemental abundances of a sample of H Ii regions in the Large and Small Magellanic Cloud. The combined optical and infrared data set gives us access to all the ionization stages of astrophysically important elements such as…
Element abundances in cool white dwarfs. II. Ultraviolet observations of DZ white dwarfs
Wolff, B.; Koester, D.; Liebert, J.
We present a small data base of homogeneously derived photospheric element abundances of DZ white dwarfs and related objects. Our previous investigations are supplemented with the analysis of ultraviolet spectra for nine white dwarfs. Of particular interest is the detection of Lalpha absorption in van Maanen 2 and a determination of the effective …
Constraining the cosmological parameters using strong lensing
Kneib, J. -P.; Soucail, G.; Golse, G.
We investigate the potential of using strong lensing clusters to constrain the cosmological parameters Omegam and Omegalambda. The existence of a multiple image system with known redshift allows, for a given (Omegam, Omegalambda) cosmology, absolute calibration of the total mass deduced from lens modelli…
Seismic tests for solar models with tachocline mixing
Antia, H. M.; Brun, A. S.; Chitre, S. M. +1 more
We have computed accurate 1-D solar models including both a macroscopic mixing process in the solar tachocline as well as up-to-date microscopic physical ingredients. Using sound speed and density profiles inferred through primary inversion of the solar oscillation frequencies coupled with the equation of thermal equilibrium, we have extracted the…
High resolution soft X-ray spectroscopy of M 87 with the reflection grating spectrometers on XMM-Newton
Böhringer, H.; Kaastra, J. S.; Branduardi-Raymont, G. +11 more
We present high-resolution X-ray spectroscopic observations of M 87 with the Reflection Grating Spectrometers on XMM-Newton. We detect strong K-shell line emission from N, O, Ne, Mg, some emission from He-like Si, a fully resolved set of Fe L-shell emission spectra, and some emission from C. The angular intensity distributions of the strong emissi…
Solar p-modes and surface magnetic fields: Is there an acoustic emission?. MDI/SOHO observations
Haber, D.; Jain, R.
We study the effect of magnetism on the surface amplitude of p-modes by creating power maps using Doppler velocity, line-depth and continuum intensity data taken by the Michelson Doppler Interferometer (MDI) instrument on board SOHO. This analysis, using proper tracking procedures, of MDI line-depth data and its comparison with the simultaneous Do…
Evolution of very small particles in the southern part of Orion B observed by ISOCAM
Perault, M.; Olofsson, G.; Boulanger, F. +19 more
We present ISOCAM observations (5-18 mu m) of the southern part of Orion B, including the reflection nebula NGC 2023 and the Horsehead nebula illuminated by the B star HD 37903 and the O star sigma Orionis, respectively. Due to the limited radiation field, the emission in these wavelengths is due to very small particles which are heated each time …
XMM-NEWTON observation of Abell 1835: Temperature, mass and gas mass fraction profiles
Reiprich, T. H.; Majerowicz, S.; Neumann, D. M.
We present a study of the medium distant cluster of galaxies Abell 1835 based on XMM-NEWTON data. The high quality of XMM-NEWTON data enable us to perform spectro-imaging of the cluster up to large radii. We determine the gas and total mass profiles based on the hydrostatic approach using the beta-model and the temperature profile. For the determi…