Search Publications

X-ray tracing using Geant4

Vacanti, G.; Buis, E. J.

We describe an extension to the Geant4 software package that allows it to be used as a general purpose X-ray tracing package. We demonstrate the use of our extension by building a model of the X-ray optics of the X-ray observatory XMM-Newton, calculating its effective area, and comparing the results with the published calibration curves.

The Hipparcos catalog. Commentary on: Perryman M. A. C., Lindegren L., Kovalevsky J., et al., 1997, A&A, 323, L49

van Leeuwen, F.

Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study

Kührt, E.; Knollenberg, J.; Motschmann, U. +3 more

The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many co…

A W UMa type system from Southern Hemisphere: CN Hydri

Bakış, V.; Özkardeş, B.; Erdem, A.

We present an analysis of the Hipparcos photometry and the high-resolution ( {λ}/{Δλ}=41000) spectroscopy of the W UMa type system CN Hyi obtained in this study for the first time. The high resolution spectroscopic observations of the system were made at Mt. John University Observatory by using HERCULES fibre-fed échelle spectrograph in September …

A review of Titan's atmospheric phenomena

Sotin, Christophe; Le Mouélic, Stéphane; Tokano, Tetsuya +2 more

Saturn’s satellite Titan is a particularly interesting body in our solar system. It is the only satellite with a dense atmosphere, which is primarily made of nitrogen and methane. It harbours an intricate photochemistry, that populates the atmosphere with aerosols, but that should deplete irreversibly the methane. The observation that methane is n…

On the origin of reverse polarity patches found by Hinode in sunspot penumbrae

Ichimoto, K.; Sánchez Almeida, J.

Context: The topology of penumbral magnetic fields is poorly known. The satellite Hinode has recently revealed penumbral structures of a magnetic polarity that is opposite to the main sunspot polarity. They may be direct confirmation that magnetic field lines and mass flows return to the solar interior throughout the penumbra, a configuration prev…

A comparison of co-temporal magnetograms obtained with the Huairou magnetograph and the Spectro-Polarimeter on board Hinode

Zhang, Hongqi; Zhang, Mei; Li, Hui +1 more

We have compared a set of co-temporal magnetograms obtained with the Solar Magnetic Field Telescope (SMFT) of the Huairou Solar Observing Station (HSOS) and with the Spectro-Polarimeter of the Solar Optical Telescope (SP/SOT) on board Hinode to check the linear calibrations of SMFT vector magnetograms. The comparison shows that the currently used …

Radial distribution of near-UV flux in disc galaxies in the range 0 ⪉ z ⪉ 1

Beckman, J. E.; Trujillo, I.; Azzollini, R.

Context: In the last 8 Gyr of cosmic time the global star formation rate (SFR) has declined by roughly an order of magnitude, and most of this activity has been progressively confined to ever less massive galaxies (“downsizing”). Previous studies show that the main drivers of the decline in the global SFR are the spiral galaxies. However, we still…

Real-time predictions of geomagnetic storms and substorms: Use of the Solar Wind Magnetosphere-Ionosphere System model

Kozyra, J.; Mays, M. L.; Horton, W. +1 more

A low-dimensional, plasma physics-based, nonlinear dynamical model of the coupled magnetosphere-ionosphere system, called Real-Time Solar Wind Magnetosphere-Ionosphere System (WINDMI), is used to predict AL and Dst values approximately 1 h before geomagnetic substorm and storm event. Subsequently, every 10 min ground-based measurements compiled by…

Studying the Imaging Characteristics of Ultra Violet Imaging Telescope (UVIT) through Numerical Simulations

Srivastava, Mudit K.; Prabhudesai, Swapnil M.; Tandon, Shyam N.

Ultra Violet Imaging Telescope (UVIT) is one of the five payloads aboard the Indian Space Research Organization (ISRO)’s ASTROSAT space mission, with broad science objectives extending from individual hot stars and star-forming regions to active galactic nuclei. The imaging performance of UVIT would depend on several factors in addition to the opt…