Search Publications
Highly variable AGN from the XMM-Newton slew survey
Read, A. M.; Esquej, P.; Miniutti, G. +4 more
Aims: We investigate the properties of a variability-selected complete sample of active galactic nuclei (AGN) in order to identify the mechanisms which cause large amplitude X-ray variability on timescales of years.
Methods: A complete sample of 24 sources was constructed, from AGN which changed their soft X-ray luminosity by more than o…
Astrometry with MCAO: HST-GeMS proper motions in the globular cluster NGC 6681
Massari, D.; Stetson, P. B.; Bono, G. +7 more
Aims: For the first time the astrometric capabilities of the Gemini Multi-Conjugate Adaptive Optics System (GeMS) facility at the Gemini South Adaptive Optics Imager (GSAOI) camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681.
Methods: Proper motions f…
On the distance to the North Polar Spur and the local CO-H2 factor
Casandjian, J. M.; Kuntz, K. D.; Lallement, R. +4 more
Aims: Most models identify the X-ray bright North Polar Spur (NPS) with a hot interstellar (IS) bubble in the Sco-Cen star-forming region at ≃130 pc. An opposite view considers the NPS as a distant structure associated with Galactic nuclear outflows. Constraints on the NPS distance can be obtained by comparing the foreground IS gas column inf…
The amazing diversity in the hot gas content of an X-ray unbiased massive galaxy clusters sample
Andreon, S.; Moretti, A.; Trinchieri, G. +1 more
We aim to determine the intrinsic variety, at a given mass, of the properties of the intracluster medium in clusters of galaxies. This requires a cluster sample selected independently of the intracluster medium content for which reliable masses and subsequent X-ray data can be obtained. We present one such sample, consisting of 34 galaxy clusters …
Unexpected spatial intensity distributions and onset timing of solar electron events observed by closely spaced STEREO spacecraft
Gómez-Herrero, R.; Dresing, N.; Heber, B. +2 more
We present multi-spacecraft observations of four solar electron events using measurements from the Solar Electron Proton Telescope (SEPT) and the Electron Proton Helium INstrument (EPHIN) on board the STEREO and SOHO spacecraft, respectively, occurring between 11 October 2013 and 1 August 2014, during the approaching superior conjunction period of…
Magnetic fields of opposite polarity in sunspot penumbrae
Franz, M.; Schmidt, W.; Solanki, S. K. +25 more
Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of this return field can only be detected indirectly by studying its imprints on strongly asymmetric and three-lobed Stokes V profiles. Infrared lines probe a narrow layer in the very deep ph…
A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255. II. Emission- and absorption-line variability time lags
Dadina, M.; Perna, M.; Trevese, D. +2 more
Context. The study of high-redshift bright quasars is crucial to gather information about the history of galaxy assembly and evolution. Variability analyses can provide useful data on the physics of quasar processes and their relation with the host galaxy.
Aims: In this study, we aim to measure the black hole mass of the bright lensed BAL QSO…
Stellar laboratories. VI. New Mo iv-vii oscillator strengths and the molybdenum abundance in the hot white dwarfs G191-B2B and RE 0503-289
Hoyer, D.; Rauch, T.; Werner, K. +3 more
Context. For the spectral analysis of high-resolution and high signal-to-noise (S/N) spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation.
Aims: To identify molybdenum lines in the…
Deep imaging of the shell elliptical galaxy NGC 3923 with MegaCam
Cuillandre, J. -C.; Gwyn, S.; Ebrová, I. +4 more
Context. The elliptical galaxy NGC 3923 is known to be surrounded by a number of stellar shells, probable remnants of an accreted galaxy. Despite its uniqueness, the deepest images of its outskirts come from the 1980s. On the basis of the modified Newtonian dynamics (MOND), it has recently been predicted that a new shell lies in this region.
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Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos fly-by
Lindqvist, M.; Molera Calvés, G.; Gurvits, L. I. +33 more
Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems.
Aims: The aim of this work is to demons…