Search Publications
A new technique to efficiently select Compton-thick AGN
Caccianiga, A.; Severgnini, P.; Della Ceca, R.
Aims: We present a new efficient diagnostic method, based on mid-infrared and X-ray data, to select local (z < 0.1) Compton-thick AGN with the aim of estimating their surface and space density.
Methods: We define a region in the X-ray-to-mid-IR [F(2-12 keV)/F25ν25] vs. X-ray color (HR) plane associated to Compton…
Spectral monitoring of RX J1856.5-3754 with XMM-Newton. Analysis of EPIC-pn data
Haberl, F.; Tiengo, A.; Mereghetti, S. +3 more
Using a large set of XMM-Newton observations, we searched for the long-term spectral and flux variability of the isolated neutron star RX J1856.5-3754 in the time interval from April 2002 to October 2011. This is the brightest and most extensively observed source of a small group of nearby, thermally emitting isolated neutron stars, of which at le…
Insights on the X-ray weak quasar phenomenon from XMM-Newton monitoring of PHL 1092
Brandt, W. N.; Fabian, A. C.; Boller, Th. +3 more
PHL 1092 is a z ∼ 0.4 high-luminosity counterpart of the class of Narrow-Line Seyfert 1 galaxies. In 2008, PHL 1092 was found to be in a remarkably low X-ray flux state during an XMM-Newton observation. Its 2 keV flux density had dropped by a factor of ∼260 with respect to a previous observation performed 4.5 yr earlier. The ultraviolet (UV) flux …
The evolution of Venus: Present state of knowledge and future exploration
Leblanc, François; Chassefière, Eric; Marty, Bernard +1 more
A detailed characterization of the formation and evolution of Venus is a key link to the study of terrestrial planets, and to their divergent evolutions. While Earth and to a lesser extent Mars (thanks to the analysis of SNC meteorites) are extensively studied in a comparative planetology context, the history of the most Earth-like planet of the S…
Dark Matter Search Using XMM-Newton Observations of Willman 1
Loewenstein, Michael; Kusenko, Alexander
We report the results of a search for an emission line from radiatively decaying dark matter in the ultra-faint dwarf spheroidal galaxy Willman 1 based on analysis of spectra extracted from XMM-Newton X-ray Observatory data. The observation follows up our analysis of Chandra data of Willman 1 that resulted in line flux upper limits over the Chandr…
The Chandra View of NGC 4178: The Lowest Mass Black Hole in a Bulgeless Disk Galaxy?
Cheung, C. C.; Böker, T.; Secrest, N. J. +3 more
Using high-resolution Chandra data, we report the presence of a weak X-ray point source coincident with the nucleus of NGC 4178, a late-type bulgeless disk galaxy known to have high-ionization mid-infrared (mid-IR) lines typically associated with active galactic nuclei (AGNs). Although the faintness of this source precludes a direct spectral analy…
Unusual quasars from the Sloan Digital Sky Survey selected by means of Kohonen self-organising maps
Meusinger, H.; Scholz, R. -D.; de Hoon, A. +4 more
Context. Large spectroscopic surveys have discovered very peculiar and hitherto unknown types of active galactic nuclei (AGN). Such rare objects may hold clues to the accretion history of the supermassive black holes at the centres of galaxies.
Aims: We aim to create a sizeable sample of unusual quasars from the unprecedented spectroscopic da…
Evidence for a Wide Range of Ultraviolet Obscuration in z ~ 2 Dusty Galaxies from the GOODS-Herschel Survey
Dickinson, Mark; Daddi, Emanuele; Dey, Arjun +20 more
Dusty galaxies at z ~ 2 span a wide range of relative brightness between rest-frame mid-infrared (8 µm) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios >~ 1000, might be abnormally bright in the…
Fe K emission from active galaxies in the COSMOS field
Sanders, D. B.; Taniguchi, Y.; Salvato, M. +14 more
We present a rest-frame spectral stacking analysis of ~1000 X-ray sources detected in the XMM-COSMOS field to investigate the iron-K line properties of active galaxies beyond redshift z ~ 1. In Type I AGN that have a typical X-ray luminosity of LX ~ 1.5 × 1044 (erg s-1) and z ~ 1.6 the cold Fe K at 6.4 keV is weak …
Aphelion water-ice cloud mapping and property retrieval using the OMEGA imaging spectrometer onboard Mars Express
Bibring, J. -P.; Gondet, B.; Langevin, Y. +8 more
Mapping of the aphelion clouds over the Tharsis plateau and retrieval of their particle size and visible opacity are made possible by the OMEGA imaging spectrometer aboard Mars Express. Observations cover the period from MY26 Ls = 330° to MY29 Ls = 180° and are acquired at various local times, ranging from 8 AM to 6 PM. Cloud…