Search Publications
Measuring the solar meridional flow from perturbations of eigenfunctions of global oscillations
Roth, M.; Schad, A.; Timmer, J.
We present a new concept to infer the meridional flow in the deep solar interior from global oscillation data. This concept is based on the estimation of the coupling strengths of p-mode eigenfunctions mediated by the meridional flow. We illustrate the performance of the method using simulations and present first inversion results of a large-scale…
Giant flux ropes observed in the magnetized ionosphere at Venus
Luhmann, J. G.; Russell, C. T.; Wei, H. Y. +10 more
The Venus ionospheric response to solar and solar wind variations is most evident in its magnetic field properties. Early Pioneer Venus observations during the solar maximum revealed that the Venus ionosphere exhibits two magnetic states depending on the solar wind dynamic pressure conditions: magnetized ionosphere with large-scale horizontal magn…
TA-DA: A Tool for Astrophysical Data Analysis
Da Rio, Nicola; Robberto, Massimo
We present the Tool for Astrophysical Data Analysis (TA-DA), a new software aimed to greatly simplify and improve the analysis of stellar photometric data in comparison with theoretical models, and allow the derivation of stellar parameters from multi-band photometry. Its flexibility allows one to address a number of such problems: from the interp…
The First Confirmed Microlens in a Globular Cluster
Minniti, D.; Udalski, A.; Pietrukowicz, P. +2 more
In 2000 July/August a microlensing event occurred at a distance of 2.33 arcmin from the center of the globular cluster M22 (NGC 6656), observed against the dense stellar field of the Milky Way bulge. We have used the adaptive optics system NACO at the ESO Very Large Telescope to resolve the two objects that participated in the event: the lens and …
The starburst-active galactic nucleus connection in the merger galaxy Mrk 938: an infrared and X-ray view
Altieri, B.; Valtchanov, I.; Esquej, P. +14 more
Mrk 938 is a luminous infrared (IR) galaxy in the local Universe believed to be the remnant of a galaxy merger. It shows a Seyfert 2 nucleus and intense star formation according to optical spectroscopic observations. We have studied this galaxy using new Herschel far-IR imaging data in addition to archival X-ray, UV, optical, near-IR and mid-IR da…
A magnetic cycle of τ Bootis? The coronal and chromospheric view
Schmitt, J. H. M. M.; Günther, H. M.; Poppenhaeger, K.
τ Bootis is a late F-type main sequence star orbited by a Hot Jupiter. During the last years spectropolarimetric observations led to the hypothesis that this star may host a global magnetic field that switches its polarity once per year, indicating a very short activity cycle of only one year duration. In our ongoing observational campaign, we hav…
Herschel/HIFI observations of red supergiants and yellow hypergiants. I. Molecular inventory
Waters, L. B. F. M.; Menten, K. M.; Olofsson, H. +17 more
Context. Red supergiant stars (RSGs) and yellow hypergiant stars (YHGs) are believed to be the high-mass counterparts of stars in the asymptotic giant branch (AGB) and early post-AGB phases. As such, they are scarcer and the properties and evolution of their envelopes are still poorly understood.
Aims: We study the mass-loss in the post main-…
A multiwavelength survey of AGN in massive clusters: AGN detection and cluster AGN fraction
Sarajedini, Vicki L.; Klesman, Alison J.
We aim to study the effect of environment on the presence and fuelling of active galactic nuclei (AGNs) in massive galaxy clusters. We explore the use of different AGN detection techniques with the goal of selecting AGN across a broad range of luminosities, AGN/host galaxy flux ratios and obscuration levels. From a sample of 12 galaxy clusters at …
A Unified and Very Fast Way for Computing the Global Potential and Linear Force-Free Fields
Feng, Xueshang; Jiang, Chaowei
We present a fast solver for computing potential and linear force-free fields (LFFF) above the full solar disk with a synoptic magnetic map as input. The global potential field and the LFFF are dealt with in a unified way by solving a three-dimensional Helmholtz equation in a spherical shell and a two-dimensional Poisson equation on the solar surf…
Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED
Lointier, G.; Simon Wedlund, C.; Trotignon, J. -G. +4 more
On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is es…