Search Publications
A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255. I. C IV absorption variability
Perna, M.; Trevese, D.; Vagnetti, F. +3 more
Context. Broad absorption lines indicate gas outflows with velocities from thousands of km s-1 to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide information on changes in the density and velocity distribut…
The Milky Way halo as a QSO absorption-line system. New results from an HST/STIS absorption-line catalogue of Galactic high-velocity clouds
Richter, P.; Charlton, J. C.; Masiero, J. R. +1 more
We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low- and intermediate ions (O i, C ii, Si ii, Mg ii, Fe ii, Si iii, C iv, and Si i…
Is the Sunyaev-Zeldovich effect responsible for the observed steepening in the spectrum of the Coma radio halo?
Brunetti, G.; Cassano, R.; Mazzotta, P. +3 more
Aims: The radio halo in the Coma cluster is unique in that its spectrum has been measured over almost two decades in frequency. The current radio data show a steepening of the spectrum at higher frequencies, which has implications for models of the radio halo origin. There is an on-going debate on the possibility that the observed steepening …
X-ray spectroscopy of the ADC source X1822-371 with Chandra and XMM-Newton
Robba, N. R.; Papitto, A.; Di Salvo, T. +5 more
Context. The eclipsing low-mass X-ray binary X1822-371 is the prototype of the accretion disc corona (ADC) sources. Its inclination angle (≃82.5°) is high enough that flux from the neutron star is blocked by the edge-on accretion disc. Because the neutron star's direct emission is hidden, its ADC emission is visible. The physical properties of the…
HST far-ultraviolet imaging of DG Tauri. Fluorescent molecular hydrogen emission from the wide opening-angle outflow
Schmitt, J. H. M. M.; Güdel, M.; Eislöffel, J. +4 more
One of the most thoroughly studied jets from all young stellar objects is the jet of DG Tau, which we imaged in the far-ultraviolet with the Hubble Space Telescope for the first time. These high spatial resolution images were obtained with long-pass filters and allow us to construct images tracing mainly H2 and C iv emission. We find th…
An archive study of 18 old novae. I. The UV spectra
Selvelli, P.; Gilmozzi, R.
Aims: We present an overview of the UV spectral properties of old novae as a class. The data and results of this paper, together with data from the outburst phases, will be utilized in a follow-up study to determine statistical properties and to investigate correlations among the physical parameters of the quiescent and eruptive phases.
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Ultraviolet and visual flux and line variations of one of the least variable Bp stars HD 64740
Skarka, M.; Krtička, J.; Janík, J. +4 more
Context. The light variability of hot magnetic chemically peculiar stars is typically caused by the flux redistribution in spots with peculiar abundance. This raises the question why some stars with surface abundance spots show significant rotational light variability, while others do not.
Aims: We study the Bp star HD 64740 to investigate ho…
The XMM-Newton SSC survey of the Galactic plane
Motch, C.; Pakull, M.; Barcons, X. +17 more
Many different classes of X-ray sources contribute to the Galactic landscape at high energies. Although the nature of the most luminous X-ray emitters is now fairly well understood, the population of low-to-medium X-ray luminosity (LX = 1027-34 erg s-1) sources remains much less studied, our knowledge being mostly …
Accretion disk wind as explanation for the broad-line region structure in NGC 5548
Kollatschny, W.; Zetzl, M.
Context. Supermassive black holes in the centers of active galactic nuclei (AGN) are surrounded by broad-line regions (BLRs). The broad emission lines seen in the AGN spectra are emitted in this spatially unresolved region.
Aims: We intend to obtain information on the structure and geometry of this BLR based on observed line profiles.
Me…
A 0535+26 in the April 2010 outburst: probing the accretion regime at work
Müller, D.; Klochkov, D.; Santangelo, A. +1 more
Context. A number of accreting X-ray pulsars experience spectral changes, both on the long time scales and on the time scales of the neutron star spin period. The sources seem to form two distinct groups that differ by the type of the spectral variations with flux. Such a bimodality probably reflects two different regimes of accretion that may res…