Search Publications
On the weakness of disc models in bright ULXs
Soria, R.; Gonçalves, A. C.
It is sometimes suggested that phenomenological power law plus cool disc-blackbody models represent the simplest, most robust interpretation of the X-ray spectra of bright ultraluminous X-ray sources (ULXs); this has been taken as evidence for the presence of intermediate-mass black holes (BHs) (M ~ 103Msolar) in those source…
Unveiling the thermal and magnetic map of neutron star surfaces though their X-ray emission: method and light-curve analysis
Turolla, Roberto; Zane, Silvia
Recent Chandra and XMM-Newton observations of a number of X-ray `dim' pulsating neutron stars have revealed quite unexpected features in the emission from these sources. Their soft thermal spectrum, believed to originate directly from the star surface, shows evidence for a phase-varying absorption line at some hundred eVs. The pulse modulation is …
Stochastic Acceleration in the Galactic Center HESS Source
Melia, Fulvio; Liu, Siming; Petrosian, Vahé +1 more
Stochastic acceleration of electrons interacting resonantly with a turbulent magnetic field in a small accretion torus appears to be the likely mechanism responsible for much of Sagittarius A*'s millimeter and shorter wavelength spectrum. The longer wavelength radiation is produced at larger radii by electrons either diffusing from smaller scales …
Simultaneous X-ray and optical observations of S5 0716+714 after the outburst of March 2004
Maraschi, L.; Tagliaferri, G.; Ghisellini, G. +6 more
At the end of March 2004, the blazar S5 0716+714 underwent an optical outburst that prompted for quasi-simultaneous target-of-opportunity observations with the INTEGRAL and XMM-Newton satellites. In this paper, we report the results of the XMM-Newton and INTEGRAL OMC data analysis. The X-ray spectrum is well-represented by a concave broken power-l…
Tracing baryons in the warm-hot intergalactic medium with broad Ly α absorption
Savage, B. D.; Sembach, K. R.; Richter, P. +1 more
We discuss physical properties and baryonic content of broad Ly α absorbers (BLAs) at low redshift. These absorption systems, recently discovered in high-resolution, high-signal to noise quasar absorption line spectra, possibly trace the warm-hot intergalactic medium (WHIM) in the temperature range between 105 and 106 K. The …
XMM-Newton observation of a spectral state transition in the peculiar radio/X-ray/γ-ray source LS I +61 303
Mereghetti, S.; Sidoli, L.; Pellizzoni, A. +3 more
We report the results of XMM-Newton and BeppoSAX observations of the radio and X-ray emitting star LS I +61 303, likely associated with the gamma-ray source 2CG 135+01 and recently detected also at TeV energies. The data include a long XMM-Newton pointing carried out in January 2005, which provides the deepest look ever obtained for this object in…
Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1
Coates, A. J.; Crary, F.; Johnson, R. E. +15 more
The Cassini Plasma Spectrometer (CAPS) instrument observed the plasma environment at Titan during the Cassini orbiter's TA encounter on October 26, 2004. Titan was in Saturn's magnetosphere during the Voyager 1 flyby and also during the TA encounter. CAPS measurements from this encounter are compared with measurements made by the Voyager 1 Plasma …
Titan's 3-micron spectral region from ISO high-resolution spectroscopy
Drossart, Pierre; Lellouch, Emmanuel; Coustenis, Athena +8 more
The near-infrared spectrum of Titan, Saturn's largest moon and one of the Cassini/Huygens' space mission primary targets, covers the 0.8 to 5 micron region in which it shows several weak CH 4 absorption regions, and in particular one centered near 2.75 micron. Due to the interference of telluric absorption, only part of this window regi…
Central Star Formation and PAH Profiles in Pseudobulges and Classical Bulges
Fisher, David B.
I use Spitzer 3.6-8.0 µm color profiles and surface brightness profiles of polycyclic aromatic hydrocarbons (PAHs) to compare the radial structure of star formation in pseudobulges and classical bulges. Pseudobulges are ``bulges'' that form through secular evolution, rather than mergers. In this study, pseudobulges are identified using the p…
A weak lensing estimate from GEMS of the virial to stellar mass ratio in massive galaxies to z ~ 0.8
Bell, Eric F.; Wisotzki, Lutz; Wolf, Christian +14 more
We present constraints on the evolution of the virial to stellar mass ratio of galaxies with high stellar masses in the redshift range 0.2 < z < 0.8, by comparing weak lensing measurements of virial mass Mvir with estimates of stellar mass Mstar. For a complete sample of galaxies with log(Mstar/Msolar