Search Publications
Anatomy of the AGN in NGC 5548. VI. Long-term variability of the warm absorber
Kaastra, J. S.; Kriss, G. A.; Bianchi, S. +13 more
Context. We observed the archetypal Seyfert 1 galaxy NGC 5548 in 2013-2014 in the context of an extensive multiwavelength campaign involving several satellites, which revealed the source to be in an extraordinary state of persistent heavy obscuration.
Aims: We re-analyzed the archival grating spectra obtained by XMM-Newton and Chandra between…
The cause of spatial structure in solar He I 1083 nm multiplet images
Joshi, Jayant; Carlsson, Mats; Leenaarts, Jorrit +2 more
Context. The He I 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, but the influence of the complex three-dimensional structure of the chromosphere and corona has however never been investiga…
A textbook example of ram-pressure stripping in the Hydra A/A780 cluster
Rossetti, M.; Molendi, S.; De Grandi, S. +7 more
In the current epoch, one of the main mechanisms driving the growth of galaxy clusters is the continuous accretion of group-scale halos. In this process, the ram pressure applied by the hot intracluster medium on the gas content of the infalling group is responsible for stripping the gas from its dark-matter halo, which gradually leads to the viri…
GK Persei and EX Hydrae: Intermediate polars with small magnetospheres
Werner, K.; Ducci, L.; Doroshenko, V. +2 more
Observed hard X-ray spectra of intermediate polars are determined mainly by the accretion flow velocity at the white dwarf surface, which is normally close to the free-fall velocity. This allows us to estimate the white dwarf masses as the white dwarf mass-radius relation M - R and the expected free-fall velocities at the surface are well known. T…
Electrical properties and porosity of the first meter of the nucleus of 67P/Churyumov-Gerasimenko. As constrained by the Permittivity Probe SESAME-PP/Philae/Rosetta
Le Gall, Alice; Seidensticker, Klaus J.; Fischer, Hans-Herbert +7 more
Context. Comets are primitive objects, remnants of the volatile-rich planetesimals from which the solar system condensed. Knowing their structure and composition is thus crucial for the understanding of our origins. After the successful landing of Philae on the nucleus of 67P/Churyumov-Gerasimenko in November 2014, for the first time, the Rosetta …
Photospheric and coronal magnetic fields in six magnetographs. I. Consistent evolution of the bashful ballerina
Mursula, Kalevi; Virtanen, Ilpo
Aims: We study the long-term evolution of photospheric and coronal magnetic fields and the heliospheric current sheet (HCS), especially its north-south asymmetry. Special attention is paid to the reliability of the six data sets used in this study and to the consistency of the results based on these data sets.
Methods: We use synoptic ma…
Revealing the broad iron Kα line in Cygnus X-1 through simultaneous XMM-Newton, RXTE, and INTEGRAL observations
Grinberg, Victoria; Pottschmidt, Katja; Staubert, Rüdiger +15 more
We report on the analysis of the broad Fe Kα line feature of Cyg X-1 in the spectra of four simultaneous hard intermediate state observations made with the X-ray Multiple Mirror mission (XMM-Newton), the Rossi X-ray Timing Explorer (RXTE), and the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The high quality of the XMM-Newton data t…
Far-infrared study of tracers of oxygen chemistry in diffuse clouds
Menten, K. M.; Neufeld, D. A.; Stutzki, J. +8 more
Context. The chemistry of the diffuse interstellar medium rests upon three pillars: exothermic ion-neutral reactions ("cold chemistry"), endothermic neutral-neutral reactions with significant activation barriers ("warm chemistry"), and reactions on the surfaces of dust grains. While warm chemistry becomes important in the shocks associated with tu…
First simultaneous SST/CRISP and IRIS observations of a small-scale quiet Sun vortex
Doyle, J. G.; Scullion, E.; Tziotziou, K. +3 more
Context. Ubiquitous small-scale vortices have recently been found in the lower atmosphere of the quiet Sun in state-of-the-art solar observations and in numerical simulations.
Aims: We investigate the characteristics and temporal evolution of a granular-scale vortex and its associated upflows through the photosphere and chromosphere of a quie…
A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta
Jorda, L.; Lara, L. M.; Lamy, P. +40 more
Context. On 12 March 2015 the OSIRIS WAC camera onboard the ESA Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed a small outburst originating from the Imhotep region at the foot of the big lobe of the comet. These measurements are unique since it was the first time that the initial phase of a transient outburst event could be d…