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Seismic Emission from A M9.5-Class Solar Flare
Cally, P. S.; Lindsey, C.; Donea, A. -C. +2 more
Following the discovery of a few significant seismic sources at 6.0 mHz from the large solar flares of October 28 and 29, 2003, we have extended SOHO/MDI helioseismic observations to moderate M-class flares. We report the detection of seismic waves emitted from the β γ δ active region NOAA 9608 on September 9, 2001. A quite impulsive solar flare o…
Microquasars as sources of positron annihilation radiation
Guessoum, N.; Jean, P.; Prantzos, N.
We consider the production of positrons in microquasars, i.e. X-ray binary systems that exhibit jets frequently, but not continuously. We estimate the production rate of positrons in microquasars, both by simple energy considerations and in the framework of various proposed models. We then evaluate the collective emissivity of the annihilation rad…
Morphology of the ultraviolet Io footprint emission and its control by Io's location
Clarke, John T.; Grodent, Denis; GéRard, Jean-Claude +1 more
A total of 74 images of the ultraviolet footprint of the Io flux tube (IFT) on Jupiter's upper atmosphere made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope have been analyzed to characterize their location, morphology, and brightness distribution. The observations cover a wide range of central meridian Jovian l…
Enceladus: A significant plasma source for Saturn's magnetosphere
Hill, T. W.; Pontius, D. H.
The Cassini Plasma Spectrometer has reported dramatic perturbations of the magnetospheric plasma flow in a region extending at least 30 satellite radii away from Saturn's small but active icy satellite Enceladus. We interpret these observations here by means of a steady state model of the electrodynamic coupling between Enceladus and Saturn. Neutr…
Ulysses observations of very different heliospheric structure during the declining phase of solar activity cycle 23
McComas, D. J.; Gosling, J. T.; Elliott, H. A. +1 more
This study examines the most recent observations from the solar wind experiment (SWOOPS) on the Ulysses spacecraft. In contrast to observations over the same locations in the declining phase of the previous solar activity cycle, these data show a more complicated heliospheric structure. Around the start of 2003, a band of slow solar wind resided a…
The clustering evolution of distant red galaxies in the GOODS-MUSIC sample
Fontana, A.; Vanzella, E.; Grazian, A. +8 more
Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies.
Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~µm) and …
Measuring supermassive black holes with gas kinematics: the active S0 galaxy NGC 3998
Marconi, A.; Capetti, A.; de Francesco, G.
Context: .We present results from a kinematical study of the gas in the nucleus of the active S0 galaxy NGC 3998 obtained from archival HST/STIS long-slit spectra.
Aims: .We analyzed the emission lines profiles and derived the map of the gas velocity field. The observed velocity curves are consistent with gas in regular rotation around the gal…
Suppression of dwarf galaxy formation by cosmic reionization
Loeb, Abraham; Wyithe, J. Stuart B.
A large number of faint galaxies, born less than a billion years after the Big Bang, have recently been discovered. Fluctuations in the distribution of these galaxies contributed to a scatter in the ionization fraction of cosmic hydrogen on scales of tens of megaparsecs, as observed along the lines of sight to the earliest known quasars. Theoretic…
Spectral Statistics and Local Luminosity Function of a Complete Hard X-Ray Sample of the Brightest Active Galactic Nuclei
Ishisaki, Y.; Ueda, Y.; Miyaji, T. +2 more
We have measured the X-ray spectral properties of a complete flux-limited sample of bright active galactic nuclei (AGNs) from the HEAO-1 all-sky catalogs to investigate their statistics and provide greater constraints on the bright end of the hard X-ray luminosity function (HXLF) and the AGN population synthesis model of the X-ray background. Spec…
Extinction Columns and Intrinsic X-Ray Spectra of the Anomalous X-Ray Pulsars
Durant, Martin; van Kerkwijk, Marten H.
The X-ray spectra of anomalous X-ray pulsars have long been fit by smooth, empirical models such as the sum of a blackbody plus a power law. These reproduce the ~0.5-10 keV range well, but fail at lower and higher energies, grossly overpredicting the optical and underpredicting the hard X-ray emission. A poorly constrained source of uncertainty in…