Search Publications
Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71 . I. Simultaneous broadband observations during November 2003
Lähteenmäki, A.; Smith, N.; Chen, W. P. +72 more
Context.Some intra-day variable, compact extra-galactic radio sources show brightness temperatures severely exceeding 1012 K, the limit set by catastrophic inverse-Compton (IC) cooling in sources of incoherent synchrotron radiation. The violation of the IC limit, actually possible under non-stationary conditions, would lead to IC avalan…
The XMM-Newton survey of the ELAIS-S1 field. I. Number counts, angular correlation function and X-ray spectral properties
Berta, S.; D'Elia, V.; Fiore, F. +16 more
Aims.The formation and evolution of cosmic structures can be probed by studying the evolution of the luminosity function of the Active Galactic Nuclei (AGNs), galaxies and clusters of galaxies and of the clustering of the X-ray active Universe, compared to the IR-UV active Universe.
Methods: .To this purpose, we have surveyed with XMM-Newton t…
Thermodynamic structure of collision-dominated expanding plasma: Heating of interplanetary coronal mass ejections
Liu, Y.; Richardson, J. D.; Kasper, J. C. +2 more
We investigate the thermodynamic structure of interplanetary coronal mass ejections (ICMEs) using combined surveys of the ejecta between 0.3 and 20 AU. ICMEs are shown to have a moderate expansion in the solar wind compared with theoretical predictions. The expansion seems to be governed by a polytrope with γ ∼ 1.3 in this distance range. We find …
A deep XMM-Newton observation of the ultraluminous X-ray source Holmberg II X-1: the case against a 1000-Msolar black hole
Uttley, P.; Reeves, J. N.; Roberts, T. P. +1 more
We present results from a 112-ks long look by XMM-Newton at the ultraluminous X-ray source (ULX) Holmberg II X-1 (Ho II X-1), long thought to be the one of best candidates for the missing class of intermediate-mass black holes (IMBHs). Our data comprises the first high-quality XMM-Newton/RGS (reflection grating spectrometer) spectrum of an ULX, an…
The Orbits of Saturn's Small Satellites Derived from Combined Historic and Cassini Imaging Observations
Porco, C. C.; Spitale, J. N.; Jacobson, R. A. +1 more
We report on the orbits of the small, inner Saturnian satellites, either recovered or newly discovered in recent Cassini imaging observations. The orbits presented here reflect improvements over our previously published values in that the time base of Cassini observations has been extended, and numerical orbital integrations have been performed in…
The Araucaria Project: The Distance to the Local Group Galaxy IC 1613 from Near-Infrared Photometry of Cepheid Variables
Soszyński, Igor; Dall'Ora, Massimo; Bono, Giuseppe +5 more
We have measured accurate near-infrared magnitudes in the J and K bands of 39 Cepheid variables in the irregular Local Group galaxy IC 1613 with well-determined periods and optical VI light curves. Using the template light curve approach of Soszyński, Gieren, & Pietrzyński, accurate mean magnitudes were obtained from these data, which allowed …
The supermassive black hole in Centaurus A: a benchmark for gas kinematical measurements
Marconi, A.; Capetti, A.; Koekemoer, A. M. +5 more
We present new HST Space Telescope Imaging Spectrograph observations of the nearby radio galaxy NGC 5128 (Centaurus A). The bright emission line with longest wavelength accessible from HST, [S III]λ 9533 Å, was used to study the kinematics of the ionized gas in the nuclear region with a 0.1 arcsec spatial resolution. The STIS data were analized in…
Multifrequency variability of the blazar AO 0235+164 . The WEBT campaign in 2004-2005 and long-term SED analysis
Lee, C. -U.; Ilyin, I.; Lähteenmäki, A. +58 more
Aims.A huge multiwavelength campaign targeting the blazar
Methods: .Monitoring observations were carried out at cm and mm wavelengths, and in the near-IR and optical bands, while three pointing…
Cassini observations of planetary-period magnetic field oscillations in Saturn's magnetosphere: Doppler shifts and phase motion
Dougherty, M. K.; Nichols, J. D.; Cowley, S. W. H. +5 more
Cassini magnetic field observations show that few-nT oscillations near the planetary rotation period, first observed in Pioneer-11 and Voyager-1 and -2 fly-by data, are essentially ubiquitous in Saturn's magnetosphere, though their character differs between the quasi-dipolar ring current region and the dawn tail. Examination of data from the ring-…
Annihilation Emission from the Galactic Black Hole
Cheng, K. S.; Chernyshov, D. O.; Dogiel, V. A.
Both diffuse high-energy gamma rays and an extended electron-positron annihilation line emission have been observed in the Galactic Center (GC) region. Although X-ray observations indicate that the Galactic black hole Sgr A* is inactive now, we suggest that Sgr A* can become active when a captured star is tidally disrupted and matter is accreted i…