Search Publications
The application of slim disk models to ULX: The case of M33 X-8
Cappelluti, N.; Grandi, P.; Rodriguez, J. +8 more
A comparative XMM-Newton archival data spectral study of the ultraluminous X-ray source (ULX) M33 X-8 has been performed by using both the standard disk model and the newly developed slim disk models. The results of this analysis tend to confirm the hypothesis that M33 X-8 is an X-ray binary with a stellar-mass black hole accreting at super-Edding…
Mapping sub-pixel surface roughness on Mars using high-resolution satellite image data
Gillespie, Alan R.; Mushkin, Amit
The ratio between co-registered pixels in stereo or repeat image pairs is used to constrain the deviation of the Martian surface from Lambertian reflection due to unresolved shadows at the pixel scale of orbiting imagers. Relative differences between the ratios primarily reflect differences in the effective amount of shadows `seen' by the sensor i…
Possibility of Excitation of Low-ℓ P-Modes by Energetic Solar Transients
Antia, H. M.; Ambastha, Ashok
We examine the temporal variation of power in low-ℓ modes using GONG data for the period of May 1995-October 2005 and compare this with disk-integrated flare and CME indices. A poor correlation between the running means of Flare Index and mode power is found. A similar result is found for CME Index also. Variations in the running mean mode power c…
An Inverse Look at the Center of M15
Chakrabarty, Dalia
The observed radial and transverse velocities of individual stars in the globular cluster M15 are used as inputs to a fully nonparametric code (CHASSIS) in order to estimate the equilibrium stellar distribution function and the three-dimensional mass density profile, from which are estimated the mass-to-light ratio, enclosed mass, and velocity dis…
On the Mass Distribution of Stars in the Solar Neighbourhood
Ninkovic, S.; Trajkovska, V.
The present authors analyse samples consisting of Hipparcos stars. Based on the corresponding HR diagrams they estimate masses of Main-Sequence stars from their visual magnitudes. They find that already beyond the heliocentric radius of 10 pc the effects of observational selection against K and M dwarfs become rather strong. For this reason the au…
Solar gravity modes: Present and future
Turck-Chièze, Sylvaine
Gravity modes are the best probes to study the solar radiative zone dynamics, especially in the nuclear core. These modes remain difficult to observe, but they are essential ingredients for progressing on the evolution of the Sun-Earth relationship at the level of centuries. Today, the knowledge of the internal dynamics comes from acoustic modes a…
On the Nature of the Ultraluminous X-Ray Transient in Cen A (NGC 5128)
Wu, Kinwah; Tennant, Allyn F.; Swartz, Douglas A. +2 more
We combine nine ROSAT, nine Chandra, and two XMM-Newton observations of the Cen A galaxy to obtain the X-ray light curve of 1RXH J132519.8-430312 (=CXOU J132519.9-430317) spanning 1990-2003. The source reached a peak 0.1-2.4 keV flux FX>10-12 ergs cm-2 s-1 during a 10 day span in 1995 July. The inferr…
Iron Depletion in the Hot Bubbles in Planetary Nebulae
Zhekov, Svetozar A.; Richer, Michael G.; Arrieta, Anabel +1 more
We have searched for the emission from [Fe X] λ6374 and [Fe XIV] λ5303 that is expected from the gas emitting in diffuse X-rays in BD +30°3639, NGC 6543, NGC 7009, and NGC 7027. Neither line was detected in any object. Models that fit the X-ray spectra of these objects indicate that the [Fe X] λ6374 emission should be below our detection threshold…
Gamma-ray constraints on the infrared background excess
Salvaterra, R.; Ferrara, A.; Mapelli, M.
Motivated by the idea that the recently detected near-infrared (1.2-4 µm) excess over the contribution of known galaxies is due to redshifted light from the first cosmic stars [MNRAS 339 (2003) 973], we have used the effect caused by photon-photon absorption on gamma-ray spectra of blazars to put constraints on extragalactic background light…
The hosts and environments of local ULIRGs and QSOs
Veilleux, Sylvain
This paper reviews the recent results from a comprehensive investigation of the most luminous mergers in the local universe, the ultraluminous infrared galaxies (ULIRGs) and the quasars. First, the frequency of occurrence and importance of black hole driven nuclear activity in ULIRGs are discussed using the latest sets of optical, near-infrared, m…