Search Publications
Coronal versus photospheric abundances of stars with different activity levels
Sanz-Forcada, J.; Micela, G.; Favata, F.
We report a detailed analysis of the coronal abundance of 4 stars with varying levels of activity and with accurately known photospheric abundances. The coronal abundance is determined here using a line flux analysis and a full determination of the differential emission measure. Photospheric abundance values are taken from the literature. Previous…
The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
Sollerman, J.; Lundqvist, P.; Shibanov, Yu. A. +1 more
The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations…
Multiband modelling of the Sun as a variable star from VIRGO/SoHO data
Pagano, I.; Lanza, A. F.; Rodonò, M.
The time series of total solar irradiance (TSI) and optical spectral irradiance at 402, 500 and 862 nm (SSIs) obtained by the VIRGO experiment on board the satellite SoHO are analysed in order to model their variability in the framework of a purely stellar-like approach. The different time scales of variability are estimated by means of the pooled…
The XMM-LSS survey. First high redshift galaxy clusters: Relaxed and collapsing systems
Altieri, B.; Valtchanov, I.; Pierre, M. +11 more
We present five newly found galaxy clusters at z>0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have sufficient spectroscopically confirmed member galaxies that an estimate of the velocity dispersion is possible: XLSSC 001 at z=0.613 and &sigma
Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud
Cook, K. H.; Freeman, K. C.; Minniti, D. +3 more
We present the radial velocities, metallicities and the K-band magnitudes of 74 RR Lyrae stars in the inner regions of the LMC. The intermediate resolution spectra and infrared images were obtained with FORS1 at the ESO VLT and with the SOFI infrared imager at the ESO NTT. The best 43 RR Lyrae with measured velocities yield an observed velocity di…
XMM-Newton discovery of a Compton-thick AGN in the GPS galaxy Mkn 668
Guainazzi, M.; Siemiginowska, A.; Rodriguez-Pascual, P. +1 more
We report the XMM-Newton discovery of the first Compton-thick obscured AGN in a Broad Line Radio Galaxy, the Gigahertz Peaked-Spectrum source Mkn 668 (OQ+208). The remarkably flat 2-10 keV X-ray spectrum (observed photon index, Γ ≃ 0.7), with a prominent iron Kα fluorescent emission line, is a clear signature of a Compton-reflection dom…
Filtration of interstellar H, O, N atoms through the heliospheric interface: Inferences on local interstellar abundances of the elements
Geiss, J.; Gloeckler, G.; Izmodenov, V. +1 more
In this Letter we report on our study of the filtration of interstellar atoms of hydrogen, oxygen and nitrogen in the interaction region between the solar wind and the local interstellar medium. The filtration has great importance for the determination of local interstellar abundances of these elements, which becomes now possible due to measuremen…
First observation of a solar X-class flare in the submillimeter range with KOSMA
Miller, M.; Lüthi, T.; Magun, A.
We present the first solar flare observations with the KOSMA submillimeter telescope at 230 and 345 GHz. The GOES X2.0 flare on April 12, 2001 was also observed at millimeter and centimeter wavelengths, as well as in soft and hard X-rays. It exhibits both an impulsive phase of nonthermal gyrosynchrotron radiation and an extended phase of strong th…
Height correction in the measurement of solar differential rotation determined by coronal bright points
Vršnak, B.; Wöhl, H.; Clette, F. +4 more
Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) are used to analyse solar differential rotation by tracing coronal bright points for the period June 4, 1998 to May 22, 1999. A method for the simultaneous determination of the true solar synodic rotation velo…
Synoptic study of the SMC SNRs using XMM-Newton
Kaastra, J. S.; Bleeker, J. A. M.; van der Heyden, K. J.
We present a detailed X-ray spectral analysis of 13 supernova remnants (SNR) in the Small Magellanic Cloud (SMC). We apply both single-temperature non-equilibrium ionisation models and models based on the Sedov similarity solution, where applicable. We also present detailed X-ray images of individual SNRs, which reveal a range of different morphol…