Search Publications
Fundamental parameters of bright Ap stars from wide-range energy distributions and advanced atmospheric models
Shulyak, D.; Ryabchikova, T.; Kochukhov, O.
Aims: As a well-established procedure for the vast majority of normal main-sequence stars, determination of atmospheric and stellar parameters turns to be a challenging process in case of magnetic chemically peculiar stars. Inhomogeneous distribution of chemical elements and strong magnetic fields make most of the standard photometric and spe…
X-ray source variability study of the M 31 central field using Chandra HRC-I
Della Valle, M.; Pietsch, W.; Haberl, F. +5 more
Context. The central field of the Andromeda galaxy (M 31) was monitored from 2006 to 2012 using the Chandra HRC-I detector (about 0.1-10 keV energy range) with the main aim of detecting X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC…
X-ray activity cycle on the active ultra-fast rotator AB Doradus A?. Implication of correlated coronal and photometric variability
Schmitt, J. H. M. M.; Lalitha, S.
Context. Although chromospheric activity cycles have been studied in a larger number of late-type stars for quite some time, very little is known about coronal activity-cycles in other stars and their similarities or dissimilarities with the solar activity cycle.
Aims: While it is usually assumed that cyclic activity is present only in stars …
Observation of SN2011fe with INTEGRAL. I. Pre-maximum phase
Zhang, X.; Hernanz, M.; Jordi, C. +19 more
Context. SN2011fe was detected by the Palomar Transient Factory in M101 on August 24, 2011, a few hours after the explosion. From the early optical spectra it was immediately realized that it was a Type Ia supernova, thus making this event the brightest one discovered in the past twenty years.
Aims: The distance of the event offered the rare …
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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