Search Publications
Strong horizontal photospheric magnetic field in a surface dynamo simulation
Schüssler, M.; Vögler, A.
Context: Observations with the Hinode spectro-polarimeter have revealed strong horizontal internetwork magnetic fields in the quiet solar photosphere.
Aims: We aim to interpret the observations with results from numerical simulations.
Methods: Radiative MHD simulations of dynamo action by near-surface convection are analyzed with respect t…
High variability in Vela X-1: giant flares and off states
Santangelo, A.; Wilms, J.; Ferrigno, C. +6 more
Aims: We investigate the spectral and temporal behavior of the high mass X-ray binary Vela X-1 during a phase of high activity, with special focus on the observed giant flares and off states.
Methods: INTEGRAL observed Vela X-1 in a long almost uninterrupted observation for two weeks in 2003 Nov/Dec. The data were analyzed with OSA 7.0 and FTO…
Transient horizontal magnetic fields in solar plage regions
Lites, B. W.; Ichimoto, K.; Ishikawa, R. +9 more
Aims:We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode.
Methods: Spectro-polarimetric observations were carried out with a cadence of 34 s for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. …
X-ray spectral evolution of TeV BL Lacertae objects: eleven years of observations with BeppoSAX, XMM-Newton and Swift satellites
Tramacere, A.; Giommi, P.; Perri, M. +2 more
Context: Many of the extragalactic sources detected in γ rays at TeV energies are BL Lac objects. In particular, they belong to the subclass of “high frequency peaked BL Lacs” (HBLs), as their spectral energy distributions exhibit a first peak in the X-ray band. At a closer look, their X-ray spectra appear to be generally curved into a log-parabol…
The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations
Solanki, S. K.; Lagg, A.; Tsuneta, S. +5 more
Context: The contrast of granulation is an important quantity characterizing solar surface convection.
Aims: We compare the intensity contrast at 630 nm, observed using the Spectro-Polarimeter (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations of Vögler & Schüssler (2007, A&A, 465, L43).
Methods: A synthetic im…
Unveiling the nature of INTEGRAL objects through optical spectroscopy. VI. A multi-observatory identification campaign
Palazzi, E.; Minniti, D.; Masetti, N. +18 more
Using 8 telescopes in the northern and southern hemispheres, plus archival data from two on-line sky surveys, we performed a systematic optical spectroscopic study of 39 putative counterparts of unidentified or poorly studied INTEGRAL sources in order to determine or at least better assess their nature. This was implemented within the framework of…
On the detectability of Lyα emission in star forming galaxies. The role of dust
Östlin, G.; Hayes, M.; Mas-Hesse, J. M. +2 more
Context: Lyman-alpha (Lyα) radiation is now widely used to investigate the galaxy formation and evolution in the high redshift universe. However, without a rigorous understanding of the processes regulating the Lyα escape fraction, physical interpretations of high-z observations remain questionable.
Aims: We examine six nearby star forming gal…
On the kinematic evolution of young local associations and the Scorpius-Centaurus complex
Figueras, F.; Torra, J.; Fernández, D.
Context: Over the last decade, several groups of young (mainly low-mass) stars have been discovered in the solar neighbourhood (closer than ~100 pc), thanks to cross-correlation between X-ray, optical spectroscopy and kinematic data. These young local associations - including an important fraction whose members are Hipparcos stars - offer insights…
Metal-rich multi-phase gas in M 87. AGN-driven metal transport, magnetic-field supported multi-temperature gas, and constraints on non-thermal emission observed with XMM-Newton
Finoguenov, A.; Böhringer, H.; Simionescu, A. +2 more
We use deep (~120 ks) XMM-Newton data of the M 87 halo to analyze its spatially resolved temperature structure and chemical composition. We focus particularly on the regions of enhanced X-ray brightness associated with the inner radio lobes, which are known not to be described very well by single-temperature spectral models. Compared to a simple t…
New observations of the extended hydrogen exosphere of the extrasolar planet HD 209458b
Ehrenreich, D.; Ferlet, R.; Vidal-Madjar, A. +6 more
Context: Atomic hydrogen escaping from the planet