Search Publications
A New Distance to the Antennae Galaxies (NGC 4038/39) Based on the Type Ia Supernova 2007sr
Schweizer, François; Madore, Barry F.; Freedman, Wendy L. +13 more
Traditionally, the distance to NGC 4038/39 has been derived from the systemic recession velocity, yielding about 20 Mpc for H 0 = 72 km s-1 Mpc-1. Recently, this widely adopted distance has been challenged based on photometry of the presumed tip of the red giant branch (TRGB), which seems to yield a shorter distanc…
X-ray spectral evolution of TeV BL Lacertae objects: eleven years of observations with BeppoSAX, XMM-Newton and Swift satellites
Tramacere, A.; Giommi, P.; Perri, M. +2 more
Context: Many of the extragalactic sources detected in γ rays at TeV energies are BL Lac objects. In particular, they belong to the subclass of “high frequency peaked BL Lacs” (HBLs), as their spectral energy distributions exhibit a first peak in the X-ray band. At a closer look, their X-ray spectra appear to be generally curved into a log-parabol…
Measuring suprathermal electron parameters in space plasmas: Implementation of the quasi-thermal noise spectroscopy with kappa distributions using in situ Ulysses/URAP radio measurements in the solar wind
Zouganelis, I.
We discuss the implementation of the quasi-thermal noise spectroscopy using kappa velocity distribution functions for the electrons. The quasi-thermal noise spectroscopy is a powerful tool for in situ space plasma diagnostics based on the analysis of the electrostatic field spectrum produced by the quasi-thermal fluctuations of electrons. The elec…
Reaching the End of the White Dwarf Cooling Sequence in NGC 6791
Anderson, Jay; Salaris, Maurizio; Bedin, Luigi R. +4 more
We present new observations of the white dwarf sequence of the old open cluster NGC 6791. The brighter peak previously observed in the white dwarf luminosity function (WDLF) is now better delineated, and the second, fainter peak that we suggested earlier is now confirmed. A careful study suggests that we have reached the end of the WD sequence. Th…
AMUSE-Virgo. I. Supermassive Black Holes in Low-Mass Spheroids
Treu, Tommaso; Marshall, Philip J.; Antonucci, Robert +3 more
We present the first results from the AGN Multiwavelength Survey of Early-Type Galaxies in the Virgo Cluster (AMUSE-Virgo). This large program targets 100 early-type galaxies with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory and the Multiband Imaging Photometer on board the Spitzer Space Telescope, with the aim of p…
INTEGRAL SPI All-Sky View in Soft Gamma Rays: A Study of Point-Source and Galactic Diffuse Emission
Bouchet, L.; Terrier, R.; Diehl, R. +4 more
We have processed the data accumulated with the INTEGRAL SPI instrument over 4 years (~51 Ms) to study the morphology of the Galactic "diffuse" emission in the 20 keV to 8 MeV energy range. To achieve this, we simultaneously derived an all-sky census of emitting sources and images of the Galactic ridge (GR) emission. In the central radian, the res…
Transient and localized processes in the magnetotail: a review
Zelenyi, L. M.; Sauvaud, J. -A.; Louarn, P. +16 more
Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes and spatial scales of a few Earth radii (RE). Examples of such transient and localized mesoscale phenomena are bursty bulk flows, beamlets, energy dispersed ion beams, flux ropes, traveling compression regions, night-side flux transfer event…
The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations
Solanki, S. K.; Lagg, A.; Tsuneta, S. +5 more
Context: The contrast of granulation is an important quantity characterizing solar surface convection.
Aims: We compare the intensity contrast at 630 nm, observed using the Spectro-Polarimeter (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations of Vögler & Schüssler (2007, A&A, 465, L43).
Methods: A synthetic im…
Mars Express and Venus Express multi-point observations of geoeffective solar flare events in December 2006
Coates, A. J.; Kallio, E.; Fedorov, A. +50 more
In December 2006, a single active region produced a series of proton solar flares, with X-ray class up to the X9.0 level, starting on 5 December 2006 at 10:35 UT. A feature of this X9.0 flare is that associated MeV particles were observed at Venus and Mars by Venus Express (VEX) and Mars Express (MEX), which were ∼80° and ∼125° east of the flare s…
Cluster observations of energetic electrons and electromagnetic fields within a reconnecting thin current sheet in the Earth's magnetotail
Eastwood, J. P.; Daly, P. W.; André, M. +12 more
We study the acceleration of energetic electrons during magnetotail reconnection by using Cluster simultaneous measurements of three-dimensional electron distribution functions, electric and magnetic fields, and waves in a thin current sheet. We present observations of two consecutive current sheet crossings where the flux of electrons 35-127 keV …