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The distribution of absorption in AGN detected in the XMM-Newton observations of the CDFS
Page, M. J.; Dwelly, T.
We have used very deep XMM-Newton observations of the Chandra Deep Field-South to examine the spectral properties of the faint active galactic nucleus (AGN) population. Crucially, redshift measurements are available for 84 per cent (259/309) of the XMM-Newton sample. We have calculated the absorption and intrinsic luminosities of the sample using …
Saturn's Spokes: Lost and Found
Porco, C. C.; Horányi, M.; Mitchell, C. J. +1 more
The spokes are intermittently appearing radial markings in Saturn's B ring that are believed to form when micrometer-sized dust particles are levitated above the ring by electrostatic forces. First observed by the Voyagers, the spokes disappeared from October 1998 until September 2005, when the Cassini spacecraft saw them reappear. The trajectorie…
XMM-Newton observations of the massive colliding wind binary and non-thermal radio emitter CygOB2#8A [O6If + O5.5III(f)]
Blomme, R.; Rauw, G.; De Becker, M. +5 more
We report on the results of four XMM-Newton observations separated by about ten days from each other of CygOB2#8A [O6If + O5.5III(f)]. This massive colliding wind binary is a very bright X-ray emitter - one of the first X-ray emitting O-stars discovered by the Einstein satellite - as well as a confirmed non-thermal radio emitter whose binarity was…
Calibration of the Soho/Lasco C3 White Light Coronagraph
Llebaria, A.; Plunkett, S. P.; Lamy, P. +16 more
We present a detailed review of the calibration of the LASCO C3 coronagraph on the SOHO satellite. Most of the calibration has been in place since early in the mission and has been utilized to varying degrees as required by specific analysis efforts. However, using observational data from the nearly decade-long database of LASCO images, we have re…
Gemini Deep Deep Survey. VI. Massive Hδ-strong Galaxies at z ~= 1
Glazebrook, Karl; McCarthy, Patrick J.; Abraham, Roberto +11 more
We show that there has been a dramatic decline in the abundance of massive galaxies with strong Hδ stellar absorption lines from z~1.2 to the present. These ``Hδ-strong'' (HDS) galaxies have undergone a recent and rapid break in their star formation activity. Combining data from the Gemini Deep Deep and Sloan Digital Sky surveys to make mass-match…
Mass Distributions of Hubble Space Telescope Galaxy Clusters from Gravitational Arcs
Bartelmann, Matthias; Meneghetti, Massimo; Comerford, Julia M. +1 more
Although N-body simulations of cosmic structure formation suggest that dark matter halos have density profiles shallower than isothermal at small radii and steeper at large radii, whether observed galaxy clusters follow this profile is still ambiguous. We use one such density profile, the asymmetric Navarro-Frenk-White (NFW) profile, to model the …
Unveiling the nature of INTEGRAL objects through optical spectroscopy. II. The nature of four unidentified sources
Palazzi, E.; Masetti, N.; Walter, R. +9 more
We present new results from our optical spectrophotometric campaign ongoing at the Astronomical Observatory of Bologna in Loiano (Italy) on hard X-ray sources detected by INTEGRAL. We have observed spectroscopically the putative optical counterparts of four more INTEGRAL sources, IGR J12391-1610, IGR J18406-0539, 2E 1853.7+1534 and IGR J19473+4452…
Oxygen abundances in metal-poor subgiants as determined from [O I], O I and OH lines
Gustafsson, B.; Asplund, M.; Nissen, P. E. +2 more
The debate on the oxygen abundances of metal-poor stars has its origin in contradictory results obtained using different abundance indicators. To achieve a better understanding of the problem we have acquired high quality spectra with the Ultraviolet and Visual Echelle Spectrograph at VLT, with a signal-to-noise of the order of 100 in the near ult…
The timing of relativistic proton acceleration in the 20 January 2005 flare
Simnett, G. M.
Understanding the energy budget in large solar flares requires a good knowledge of how and where the energetic charged particles are accelerated. If they are mainly accelerated by a Coronal Mass Ejection (CME)-driven shock, then they do not have to derive their energy from the flare region. Conversely, if the CME does not accelerate the particles,…
Heliospheric magnetic field polarity inversions driven by radial velocity field structures
Landi, Simone; Hellinger, Petr; Velli, Marco
Magnetic field polarity inversions embedded in the predominantly unipolar fast solar wind have been observed by the Ulysses spacecraft at high latitudes. Such reversals have the nature of folded back field lines which we suggest are generated by the interaction of standard large amplitude, low frequency, Alfvénic turbulence with velocity shears in…