Search Publications
Distribution of coronal heating in a solar active region
Gontikakis, C.; Contopoulos, I.; Dara, H. C.
Aims: We investigate the distribution of heating of coronal loops in a non-flaring solar active region, using a simple electrodynamic model: the random displacements of the loop footpoints, caused by photospheric plasma motions, generate electric potential differences between the footpoints and, as a result, electric currents flow along the loops,…
Spectroscopic distances of 28 nearby star candidates
Stecklum, B.; Jahreiß, H.; Meusinger, H. +1 more
Aims: Twenty eight hitherto neglected candidates for the Catalogue of Nearby Stars (CNS) were investigated to verify their classification and to improve their distance estimates. All targets had at least a preliminary status of being nearby dwarf stars based on their large proper motions and relatively faint magnitudes. Better photometric and/or s…
Q2237+0305 in X-rays: spectra and variability with XMM-Newton
Vignali, C.; Palumbo, G. G. C.; Fedorova, E. V. +1 more
Aims: X-ray observations of gravitationally lensed quasars may allow us to probe the inner structure of the central engine of a quasar. Observations of Q2237+0305 (Einstein Cross) in X-rays may be used to constrain the inner structure of the X-ray emitting source.
Methods: Here we analyze the XMM-Newton observation of the quasar in the gravita…
Far-infrared spectroscopic observations of the Galactic center region
Nakagawa, T.; Okada, Y.; Spaans, M. +2 more
Context: The Galactic center region is luminous in the far-infrared (FIR), but dominant sources of this luminosity are still controversial.
Aims: We investigate physical conditions of the diffuse interstellar medium in the Galactic center region by multi-line spectroscopy in the FIR.
Methods: We analyze the archival data of the Galactic ce…
Physical and kinematical properties of the X-ray absorber in the broad absorption line quasar APM 08279+5255
Ramírez, J. M.
Context: We have re-analyzed the X-ray spectra of the gravitational lensed high-redshift BAL QSO APM 08279+5255, observed with the XMM-Newton and Chandra observatories. Previous studies (Hasinger et al. 2002, ApJ, 573, L77; Chartas et al. 2002, ApJ, 579, 169) detected unusual, highly-ionized iron absorption features, but differed in their interpre…
Post-hoc derivation of SOHO Michelson doppler imager flat fields
Potts, H. E.; Diver, D. A.
Context: The SOHO satellite now offers a unique perspective on the Sun as it is the only space-based instrument that can provide large, high-resolution data sets over an entire 11-year solar cycle. This unique property enables detailed studies of long-term variations in the Sun. One significant problem when looking for such changes is determining …
The 2007 outburst of the X-ray binary XTE J1856+053
Greiner, J.; Sala, G.; Ajello, M. +1 more
Aims: On 28 February 2007 a new outburst of the previously known transient source XTE J1856+053 was detected with RXTE/ASM. We present here the results of an XMM-Newton (0.5-10.0 keV) Target of Opportunity observation performed on 14 March 2007, aimed at constraining the mass of the compact object in this X-ray binary and determining its main prop…
Meteoroid and space debris impacts in grazing-incidence telescopes
Carpenter, J. D.; Wells, A.; Abbey, A. F. +1 more
Context: Micrometeoroid or space debris impacts have been observed in the focal planes of the XMM-Newton and Swift-XRT (X-ray Telescope) X-ray observatories. These impacts have resulted in damage to, and in one case the failure of, focal-plane Charge-Coupled Device (CCDs) detectors.
Aims: We aim to quantify the future risks of focal-plane impa…
The X-ray emission of the most luminous 3CR radio sources
Salvati, M.; Risaliti, G.; Véron, P. +1 more
Context: Although many radio-loud quasars and galaxies have been observed in X-rays, systematic studies of well defined samples are rare.
Aims: We investigate the X-ray properties of the most luminous radio sources in the 3CR catalogue, in order to assess whether they are similar to the most luminous radio-quiet quasars, for instance in the X-…
The emission-line spectrum of the UV deficient quasar Ton 34: evidence of shock excitation?
Binette, L.; Krongold, Y.
Context: Emission lines in quasars are believed to originate from a photoionized plasma. There are, however, some emission features that appear to be collisionally excited, such as the Fe II multiplet bands. Shortward of Lyα, there are also a few permitted lines of species from low to intermediate ionization.
Aims: Ton 34 (z_q=1.928) exhibits …