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The stellar halo of the edge-on galaxy NGC 891
Rejkuba, M.; Mouhcine, M.; Ibata, R.
Using the Advanced Camera for Surveys on board the Hubble Space Telescope, we have resolved individual red giant branch stars in the outskirts of the edge-on galaxy NGC 891, down to ~2 mag fainter than the tip of the red giant branch. The data set allows investigation of the stellar populations in the outer regions of an analogue galaxy to the Mil…
Timing evidence in determining the accretion state of the Seyfert galaxy NGC 3783
Uttley, P.; Arévalo, P.; McHardy, I. M. +2 more
Previous observations with the Rossi X-ray Timing Explorer (RXTE) have suggested that the power spectral density (PSD) of NGC 3783 flattens to a slope near zero at low frequencies, in a similar manner to that of Galactic black hole X-ray binary systems (GBHs) in the `hard' state. The low radio flux emitted by this object, however, is inconsistent …
Martian ice cloud distribution obtained from SPICAM nadir UV measurements
Montmessin, Franck; Bertaux, Jean-Loup; Fussen, Didier +6 more
The Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument on board Mars Express has successfully performed one Martian year of measurements. Nadir UV (200-310 nm) measurements allowed it to build maps of ice cloud optical depth distribution for all seasons. The development and decay of the aphelion…
Earthward flowing plasmoid: Structure and its related ionospheric signature
Zong, Q. -G.; Daly, P. W.; Baker, D. N. +11 more
An earthward moving plasmoid has been observed on 28 October 2002 by the Cluster spacecraft with simultaneous auroral viewing by the IMAGE satellite. This offers the opportunity to ascertain the optical and the evolutional signatures in the ionosphere of the earthward moving plasmoid. The ionospheric signatures observed in this paper are not subst…
Water vapor and silicon monoxide maser observations in the protoplanetary nebula OH 231.8+4.2
Sánchez Contreras, C.; Alcolea, J.; Bujarrabal, V. +2 more
Context: OH 231.8+4.2 is a well studied preplanetary nebula (pPN) around a binary stellar system that shows a remarkable bipolar outflow.
Aims: To study the structure and kinematics of the inner 10-80 AU nebular regions probed by SiO and H2O maser emission, where the agents of wind collimation are expected to operate, in order to gain insights…
Transition Region Emission and Energy Input to Thermal Plasma during the Impulsive Phase of Solar Flares
Raymond, John C.; Ciaravella, A.; Kohl, J. +3 more
The energy released in a solar flare is partitioned between thermal and nonthermal particle energy and lost to thermal conduction and radiation over a broad range of wavelengths. It is difficult to determine the conductive losses and the energy radiated at transition region temperatures during the impulsive phases of flares. We use UVCS measuremen…
Global and local disturbances in the magnetotail during reconnection
Nakamura, R.; Lucek, E. A.; Rème, H. +2 more
We examine Cluster observations of a reconnection event at xGSM=-15.7 RE in the magnetotail on 11 October 2001, when Cluster recorded the current sheet for an extended period including the entire duration of the reconnection event. The onset of reconnection is associated with a sudden orientation change of the ambient magneti…
XMM-Newton observations of the Lockman Hole. V. Time variability of the brightest AGN
Page, M. J.; Barcons, X.; Fabian, A. C. +4 more
This paper presents the results of a study of X-ray spectral and flux variability on time scales from months to years, of the 123 brightest objects (including 46 type-1 AGN and 28 type-2 AGN) detected with XMM-Newton in the Lockman Hole field. We detected flux variability with a significance ≥3σ in ~50% of the objects, including 68 ± 11% and 48 ± …
Hybrid simulation of Titan's magnetic field signature during the Cassini T9 flyby
Dougherty, M. K.; Glassmeier, K. -H.; Bertucci, C. +6 more
Titan's induced magnetotail is analyzed in terms of a three-dimensional hybrid model, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. Since during the T9 flyby of Cassini, the spacecraft passed through Titan's induced magnetotail in a distance of about 4 Titan ra…
Five years of SGR 1900+14 observations with BeppoSAX
Tiengo, A.; Mereghetti, S.; Sidoli, L. +3 more
We present a systematic analysis of all the BeppoSAX data of the soft gamma-ray repeater SGR 1900+14: these observations allowed us to study the long term properties of the source quiescent emission. In the observation carried out before the 1998 giant flare the spectrum in the 0.8-10 keV energy range was harder and there was evidence for a 20-150…