Search Publications
Extreme helium stars: non-LTE matters. Helium and hydrogen spectra of the unique objects V652 Her and HD 144941
Butler, K.; Heber, U.; Przybilla, N. +1 more
Quantitative analyses of low-mass hydrogen-deficient (super-)giant stars - so-called extreme helium stars - to date face two major difficulties. First, theory fails to reproduce the observed helium lines in their entirety, wings and line cores. Second, a general mismatch exists for effective temperatures derived from ionization equilibria and from…
Nonlinear decay of foreshock Langmuir waves in the presence of plasma inhomogeneities: Theory and Cluster observations
Krasnoselskikh, V.; Dudok de Wit, T.; Soucek, J. +2 more
The intense high-frequency electrostatic waves observed in the terrestrial foreshock often have a form of a superposition of two monochromatic waves close to the plasma frequency. We suggest an interpretation of these spectra as signatures of nonlinear decay of Langmuir waves to electron-sound and ion-sound secondary waves. This decay instability …
October/November 2003 interplanetary coronal mass ejections: ACE/EPAM solar energetic particle observations
Lario, D.; Lanzerotti, L. J.; Sarris, E. T. +3 more
In late October and early November 2003 the ACE spacecraft at 1 AU detected two shock-associated interplanetary coronal mass ejections (ICMEs). In the sheath region formed in front of both ICMEs, some of the highest speeds ever directly measured in the solar wind were observed. We analyze in detail the energetic particle signatures measured at 1 A…
INTEGRAL SPI Observation of the Galactic Central Radian: Contribution of Discrete Sources and Implication for the Diffuse Emission
Bouchet, L.; Terrier, R.; Diehl, R. +4 more
The INTEGRAL observatory has been performing a deep survey of the Galactic central radian since 2003, with the goal of both extracting a catalog of sources and gaining insight into the Galactic diffuse emission. This paper concentrates on the estimation of the total point-source emission contribution. It is now clear that unresolved point sources …
Disk-integrated Intensity Pseudomodes Measured by SOHO/VIRGO
Jiménez-Reyes, S. J.; García, R. A.; Jiménez, A.
The high-frequency spectrum above the acoustic cutoff frequency (νac) of the solar atmosphere has been observed in velocity measurements at low and high angular degrees and reveals significant evidence for the presence of pseudomodes characterized by their equally spaced signal. In this paper we study this region of the spectra using fo…
Central Blue Clumps in Elliptical Galaxies of the Hubble Ultra Deep Field
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Ferguson, Thomas E.
Elliptical galaxies larger than 10 pixels in the Hubble Ultra Deep Field (UDF) were surveyed for internal structure; 30 out of 100 in a sample of 884 morphologically classified galaxies exhibit large blue clumps near their centers. Unsharp-masked images of the clearest cases are presented. The distributions of the clumps on color-color and color-m…
Chandrayaan-1: Science goals
Bhandari, N.
The primary objectives of the Chandrayaan-1 mission are simultaneous chemical, mineralogical and topographic mapping of the lunar surface at high spatial resolution. These data should enable us to understand compositional variation of major elements, which in turn, should lead to a better understanding of the stratigraphic relationships between va…
Magnetic Clouds Observed at 1 Au During the Period 2000-2003
Nieves-Chinchilla, T.; Hidalgo, M. A.; Sequeiros, J.
In this work we have performed a systematic study of all the magnetic clouds identified in the time interval 2000-2003. The study shows that the non force-free model of Hidalgo is a good approximation to the magnetic topology of the MCs in the interplanetary medium. This conclusion is reached based on the good fits obtained with the model for most…
W Hya through the eye of Odin. Satellite observations of circumstellar submillimetre H2O line emission
Olofsson, H.; Justtanont, K.; Larsson, B. +10 more
We present Odin observations of the AGB star W Hya in the ground-state transition of ortho-H{2}O, 1{10}-101, at 557 GHz. The line is clearly of circumstellar origin. Radiative transfer modelling of the water lines observed by Odin and ISO results in a mass-loss rate of (2.5±0.5)×10-7 M⊙ yr-1, and a circu…
Solar wind from the coronal hole boundaries
Geiss, J.; McComas, D. J.; Schwadron, N. A. +3 more
Recent studies using in situ observations established that the interface between fast and slow wind in interplanetary space has two distinct parts: a smoothly varying boundary layer flow that flanks fast wind from coronal holes and a sharper plasma discontinuity between intermediate and slow solar wind. Other studies using in situ observations and…