Search Publications
Accretion Disk Illumination in Schwarzschild and Kerr Geometries: Fitting Formulae
Fukumura, Keigo; Kazanas, Demosthenes
We describe the methodology and compute the illumination of geometrically thin accretion disks around black holes of arbitrary spin parameter a exposed to the radiation of a pointlike isotropic source at arbitrary height above the disk on its symmetry axis. We then provide analytic fitting formulae for the illumination as a function of the source …
Dynamical Models of Elliptical Galaxies in z = 0.5 Clusters. I. Data-Model Comparison and Evolution of Galaxy Rotation
van Dokkum, Pieter G.; van der Marel, Roeland P.
We present spatially resolved stellar rotation velocity and velocity dispersion profiles from Keck/LRIS absorption-line spectra for 25 galaxies, mostly visually classified ellipticals, in three clusters at z~0.5. We interpret the kinematical data and HST photometry using oblate axisymmetric two-integral f(E,Lz) dynamical models based on…
Radio Lobes of Pictor A: An X-Ray Spatially Resolved Study
Brunetti, Gianfranco; Grandi, Paola; Migliori, Giulia +2 more
A new XMM-Newton observation has made possible a detailed study of both lobes of the radio galaxy Pictor A. Their X-ray emission is of nonthermal origin and due to inverse Compton scattering of cosmic microwave background (CMB) photons by relativistic electrons in the lobes, as previously found. In both lobes, the equipartition magnetic field (B
Radial Profile and Lognormal Fluctuations of the Intracluster Medium as the Origin of Systematic Bias in Spectroscopic Temperature
Dolag, Klaus; Suto, Yasushi; Kitayama, Tetsu +4 more
The origin of the recently reported systematic bias in the spectroscopic temperature of galaxy clusters is investigated using a cosmological hydrodynamic simulation. We find that the local inhomogeneities of the gas temperature and density, after being corrected for their global radial profiles, have a nearly universal distribution that resembles …
The Mass Distribution of the Central Stars of Planetary Nebulae in the Large Magellanic Cloud
Villaver, Eva; Shaw, Richard A.; Stanghellini, Letizia
We present the properties of the central stars from a sample of 54 planetary nebulae (PNe) observed in the Large Magellanic Cloud (LMC) with the Hubble Space Telescope Imaging Spectrograph (STIS). The Hubble Space Telescope's spatial resolution allows us to resolve the central star from its nebula (and line-of-sight stars) at the distance of the L…
A Low-Mass H2 Component to the AU Microscopii Circumstellar Disk
Redfield, Seth; Roberge, Aki; France, Kevin +2 more
We present a determination of the molecular gas mass in the AU Microscopii circumstellar disk. Direct detection of a gas component to the AU Mic disk has proven elusive, with upper limits derived from ultraviolet absorption line and submillimeter CO emission studies. Fluorescent emission lines of H2, pumped by the O VI λ1032 resonance l…
Integral-Field Spectroscopy of the Post-Red Supergiant IRC +10420: Evidence for an Axisymmetric Wind
Sahu, Kailash C.; Davies, Ben; Oudmaijer, René D.
We present NAOMI/OASIS adaptive-optics-assisted integral-field spectroscopy of the transitional massive hypergiant IRC +10420, an extreme mass-losing star apparently in the process of evolving from a red supergiant toward the Wolf-Rayet phase. To investigate the present-day mass-loss geometry of the star, we study the appearance of the line emissi…
A Synthetic Spectrum and Light-Curve Analysis of the Cataclysmic Variable IX Velorum
Szkody, Paula; Sion, Edward M.; Godon, Patrick +2 more
Spectrum synthesis analysis of FUSE and STIS spectra for the cataclysmic variable IX Vel shows that it is possible to achieve a close synthetic spectrum fit with a mass transfer rate of M˙=5×10-9 Msolar yr-1 and a modified standard model temperature profile. The innermost four annuli of the accretion disk model, ex…
The Linear Sensitivity of Helioseismic Ring Diagrams to Local Flows
Birch, A. C.; Gizon, L.; Hindman, B. W. +1 more
Ring-diagram analysis is a technique of local helioseismology used to infer plasma flows in the solar convection zone which generates intermediate data products known as ring-fitting parameters. Knowing the sensitivity of ring-fitting parameters to actual flows in the Sun is important for interpreting these measurements. Working in plane-parallel …
X-Ray and Optical Variability of the Ultraluminous X-Ray Source NGC 1313 X-2
Falomo, R.; Treves, A.; Turolla, R. +2 more
We present an analysis of recent XMM-Newton and HST archive data of the ultraluminous X-ray source NGC 1313 X-2. Quasi-simultaneous observations taken with XMM-Newton, HST, and VLT allow us to study both the X-ray light curve and its correlation with the optical emission of the two proposed counterparts of the ultraluminous X-ray source (ULX). At …