Search Publications
Photometric observations of Rosetta target asteroid 2867 Steins
Lowry, S. C.; Weissman, P. R.; Choi, Y. -J.
Asteroid 2867 Steins is one of two flyby targets of ESA's International Rosetta Mission, launched in March, 2004. We obtained CCD observations of Steins on April 14-16, 2004 at Table Mountain Observatory, California, in order to characterize the asteroid physically, information that is crucial for planning the Steins flyby. This study includes the…
Turbulent propagation of high-energy electrons in a solar coronal loop
Melnikov, V. F.; Stepanov, A. V.; Shibasaki, K. +1 more
Aims:We study the solar flare on 28 August 1999 observed by the Nobeyama Radioheliograph at 17 and 34 GHz and analyze the unusual behavior of microwave source (a coronal loop) after injections of high-energy electrons. The observations reveal a propagation velocity of the emission front along the loop of about 104 km s-1, whi…
A precessing accretion disc in the intermediate polar XY Arietis?
Mukai, K.; Norton, A. J.
Context: XY Ari is the only intermediate polar to show deep X-ray eclipses of its white dwarf. Previously published observations with Ginga and Chandra have also revealed a broad X-ray orbital modulation, roughly antiphased with the eclipse, and presumed to be due to absorption in an extended structure near the edge of an accretion disc. The X-ray…
An ultraluminous supersoft source with a 4 hour modulation in NGC 4631
Ehle, M.; Wilms, J.; King, A. R. +2 more
Context: Supersoft X-ray sources (SSSs) are characterised by very low temperatures (<100 eV). Classical SSSs have bolometric luminosities in the range of 1036-1038 erg s-1 and are modelled with steady nuclear burning of hydrogen on the surfaces of white dwarfs. However, several SSSs have been discovered with muc…
MHD evolution of a fragment of a CME core in the outer solar corona
Orlando, S.; Peres, G.; Reale, F. +1 more
Context: Detailed hydrodynamic modeling explained several features of a fragment of the core of a Coronal Mass Ejection observed with SoHO/UVCS at 1.7 R⊙ on 12 December 1997, but some questions remained unsolved.
Aims: We investigate the role of the magnetic fields in the thermal insulation and the expansion of an ejected fragment (…
Eclipsed X-ray flares in binary stars: geometrical constraints on the flare's location and size
Sanz-Forcada, J.; Micela, G.; Favata, F.
Aims: The observation of eclipses during X-ray flares taking place in active cool stars binaries allows us to calculate the position and size of the flares. This information cannot be derived by analyzing the decay of the flares, a frequently used approach in the literature that requires the assumption of a physical model. We make use of the eclip…
Monte Carlo simulations of metal-poor star clusters
Degl'Innocenti, S.; Raimondo, G.; Fagiolini, M.
Context: Metal-poor globular clusters (GCs) can provide a probe of the earliest epoch of star formation in the Universe, being the oldest observable stellar systems. In addition, young and intermediate-age low-metallicity GCs are present in external galaxies. Nevertheless, inferring their evolutionary status by using integrated properties may suff…
Unbinned maximum-likelihood estimators for low-count data. Applications to faint X-ray spectra in the Taurus molecular cloud
Audard, M.; Güdel, M.; Franciosini, E. +5 more
Traditional binned statistics such as χ2 suffer from information loss and arbitrariness of the binning procedure, which is especially important at low count rates as encountered in the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). We point out that the underlying statistical quantity (the log likelihood L) does not re…
Multiscale optical flow probing of dynamics in solar EUV images. Algorithm, calibration, and first results
Hochedez, J. -F.; Gissot, S. F.
Context: Movies of the solar atmosphere reveal motion and variations in brightness. In particular, sequences of coronal images exhibit the plane-of-the-sky component of the velocity combined with other variations in the signal. The present work analyses solar extreme-ultraviolet images, as recorded by the Extreme ultraviolet Imaging Telescope (EIT…
Statistics of superimposed flares in the Taurus molecular cloud
Audard, M.; Güdel, M.; Telleschi, A. +2 more
Context: Stochastically occurring flares provide a possible mechanism of coronal heating in magnetically active stars such as T Tauri objects in star-forming regions.
Aims: We investigate the statistics of stellar X-ray light curves from the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST).
Methods: To this end, the light cu…