Search Publications
Phase-Resolved Spectroscopy of Geminga Shows Rotating Hot Spot(s)
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +2 more
Isolated neutron stars are seen in x-rays through their nonthermal and/or surface thermal emissions. X-ray Multimirror Mission-Newton observations of the Geminga pulsar show a 43-electron volt spectrum from the whole neutron star surface, as well as a power-law component above 2 kiloelectron volts. In addition, we have detected a hot (170 electron…
Measuring Stellar Differential rotation with asteroseismology
Solanki, Sami K.; Gizon, Laurent
The variation of rotation with latitude is poorly known on stars other than the Sun. Several indirect techniques, photometric and spectroscopic, have been used to search for departure from rigid rotation for sufficiently fast rotators. Here we investigate the possibility of measuring stellar differential rotation for solar-type stars through aster…
Detection of Hard X-Ray Emission from the Galactic Nuclear Region with INTEGRAL
Goldoni, P.; Parmar, A. N.; Ubertini, P. +13 more
This Letter presents the first results of an observational campaign to study the Galactic center with INTEGRAL, the International Gamma-Ray Astrophysics Laboratory. Mosaicked images were constructed using data obtained with ISGRI, the soft gamma-ray instrument of the coded aperture IBIS imager, in the energy ranges 20-40 and 40-100 keV. These give…
η Carinae's Brightness Variations Since 1998: Hubble Space Telescope Observations of the Central Star
Martin, J. C.; Koppelman, M. D.
We have measured the brightness variations in η Carinae for the past 6 years using the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph and Advanced Camera for Surveys. Unlike ground-based data, observations by the HST allow direct measurement of the brightness of the central star by resolving it from the surrounding bright ejecta…
Three-fluid model of the heating and acceleration of the fast solar wind
Ofman, L.
A new three-fluid, two-dimensional, wave-driven model that includes, for the first time, heat conduction, viscous, and resistive dissipation for protons and electrons in two-dimensional coronal hole is presented. The fast solar wind model includes electron, proton, and He++ or O5+ ion fluids. The heating of the solar wind pla…
Chandra and XMM-Newton Observations of the Double Cluster A1758
David, Laurence P.; Kempner, Joshua
A1758 was classified by Abell as a single rich cluster of galaxies, but a ROSAT observation showed that this system consists of two distinct clusters (A1758N and A1758S) separated by approximately 8' (a projected separation of 2 Mpc in the rest frame of the clusters). Only a few galaxy redshifts have been published for these two clusters, but the …
FUSE observations of the H I interstellar gas of I Zw 18
Kunth, D.; Lebouteiller, V.; Lecavelier des Etangs, A. +5 more
We present the analysis of FUSE observations of the metal-deficient dwarf galaxy I Zw 18 . We measured column densities of H I, N I, O I, Ar I, Si II, and Fe II. The O I/H I ratio (\log(O I/H I)=-4.7+0.8-0.6) is consistent with the O/H ratio observed in the H II regions (all uncertainties are 2-σ). If the oxygen is depleted i…
Hydromagnetic Wave Excitation Upstream of an Interplanetary Traveling Shock
Klecker, B.; Wimmer-Schweingruber, R. F.; Hilchenbach, M. +5 more
Using data of the Highly Suprathermal Time-Of-Flight sensor of the Charge, Element, and Isotope Analysis System on board the Solar and Heliospheric Observatory spacecraft located at Lagrangian point L1 near Earth, we have measured proton spectra in the energy range 60 keV-2 MeV associated with the Bastille Day coronal mass ejection of 2000 July 14…
A dipping black hole X-ray binary candidate in NGC 55
Warwick, R. S.; Roberts, T. P.; Stobbart, A. -M.
XMM-Newton European Photon Imaging Camera (EPIC) observations have revealed a bright point-like X-ray source in the nearby Magellanic-type galaxy NGC 55. At the distance of NGC 55, the maximum observed X-ray luminosity of the source, designated as XMMU J001528.9 - 391319, is Lx ~ 1.6 × 1039 erg s-1, placing the obj…
A three-dimensional model of moist convection for the giant planets II: Saturn's water and ammonia moist convective storms
Hueso, Ricardo; Sánchez-Lavega, Agustín
Moist convective storms constitute a key aspect in the global energy budget of the atmospheres of the giant planets. Among them, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots (GWS) which occur rarely and have been detected once every 30 years approximately. On the average, Saturn seems to…