Search Publications
A systematic study of variability among OB-stars based on HIPPARCOS photometry
Lefèvre, L.; Moffat, A. F. J.; Marchenko, S. V. +1 more
Context: Variability is a key factor for understanding the nature of the most massive stars, the OB stars. Such stars lie closest to the unstable upper limit of star formation.
Aims: In terms of statistics, the data from the HIPPARCOS satellite are unique because of time coverage and uniformity. They are ideal to study variability in this larg…
Forbush decreases and turbulence levels at coronal mass ejection fronts
Antia, H. M.; Subramanian, P.; Kojima, H. +14 more
Aims: We seek to estimate the average level of MHD turbulence near coronal mass ejection (CME) fronts as they propagate from the Sun to the Earth.
Methods: We examined the cosmic ray data from the GRAPES-3 tracking muon telescope at Ooty, together with the data from other sources for three closely observed Forbush decrease events. Each of thes…
Propagating waves in polar coronal holes as seen by SUMER & EIS
Solanki, S. K.; Teriaca, L.; Gupta, G. R. +3 more
Context: To study the dynamics of coronal holes and the role of waves in the acceleration of the solar wind, spectral observations were performed over polar coronal hole regions with the SUMER spectrometer on SoHO and the EIS spectrometer on Hinode.
Aims: Using these observations, we aim to detect the presence of propagating waves in the coron…
Molecular gas in NUclei of GAlaxies (NUGA). XI. A complete gravity torque map of NGC 4579: new clues to bar evolution
Hunt, L. K.; Krips, M.; Schinnerer, E. +6 more
In this paper we create a complete gravity torque map of the disk of the LINER/Seyfert 1.9 galaxy NGC 4579. We quantify the efficiency of angular momentum transport and search for signatures of secular evolution in the fueling process from r ~ 15 kpc down to the inner r ~ 50 pc around the active galactic nucleus (AGN). We use both the 1-0 and 2-1 …
Updating the orbital ephemeris of Hercules X-1; rate of decay and eccentricity of the orbit
Klochkov, D.; Wilms, J.; Staubert, R.
We present an update of the orbital ephemeris of the binary X-ray pulsar Her X-1 and determine an improved value for the rate of orbital decay. In addition, we report the first measurement of the orbital eccentricity. We analyzed pulse timing data of Her X-1 from X-ray observations by RXTE (Rossi X-Ray Timing Explorer) and INTEGRAL over the period…
Noise properties of the CoRoT data. A planet-finding perspective
Mazeh, T.; Guterman, P.; Aigrain, S. +30 more
In this short paper, we study the photometric precision of stellar light curves obtained by the CoRoT satellite in its planet-finding channel, with a particular emphasis on the time scales characteristic of planetary transits. Together with other articles in the same issue of this journal, it forms an attempt to provide the building blocks for a s…
Transit mapping of a starspot on CoRoT-2. Probing a stellar surface with planetary transits
Schmitt, J. H. M. M.; Czesla, S.; Guenther, E. W. +4 more
We analyze variations in the transit lightcurves of CoRoT-2b, a massive hot Jupiter orbiting a highly active G star. We use one transit lightcurve to eclipse-map a photospheric spot occulted by the planet. In this case study we determine the size and longitude of the eclipsed portion of the starspot and systematically study the corresponding uncer…
Evolution of the early-type galaxy fraction in clusters since z = 0.8
Pelló, R.; White, S. D. M.; Milvang-Jensen, B. +13 more
We study the morphological content of a large sample of high-redshift clusters to determine its dependence on cluster mass and redshift. Quantitative morphologies are based on PSF-convolved, 2D bulge+disk decompositions of cluster and field galaxies on deep Very Large Telescope FORS2 images of eighteen, optically-selected galaxy clusters at 0.45 &…
Model atmospheres of chemically peculiar stars. Self-consistent empirical stratified model of HD 24712
Shulyak, D.; Ryabchikova, T.; Kochukhov, O. +1 more
Context: High-resolution spectra of some chemically peculiar stars clearly demonstrate the presence of strong abundance gradients in their atmospheres. However, these inhomogeneities are usually ignored in the standard scheme of model atmosphere calculations, breaking the consistency between model structure and spectroscopically derived abundance …
Multi-wavelength study of X-ray luminous clusters at z ~ 0.3. I. Star-formation activity of cluster galaxies
Böhringer, H.; Biviano, A.; Pierini, D. +1 more
Context: The current paradigm of cosmic formation and evolution of galaxy clusters foresees growth mostly through merging. Galaxies in the infall region or in the core of a cluster undergo transformations owing to different environmental stresses.
Aims: For two X-ray luminous clusters at redshift z 0.3 with opposite X-ray morphologies (i.e., d…