Search Publications
Towards an understanding of the Of?p star HD191612: phase-resolved multiwavelength observations
Walborn, Nolan R.; Nazé, Yaël; Howarth, Ian D. +2 more
We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a period of 538d and its spectrum was found to present the signature of a magnetic field. In the X-rays, it is slightly overluminous compared to the canonic…
Fe K Line Profile in Low-Redshift Quasars: Average Shape and Eddington Ratio Dependence
Ho, Luis C.; Terashima, Yuichi; Inoue, Hirohiko
We analyze X-ray spectra of 43 Palomar-Green quasars observed with XMM-Newton in order to investigate their mean Fe K line profile and its dependence on physical properties. The continuum spectra of 39 objects are well reproduced by a model consisting of a power law and a blackbody modified by Galactic absorption. The spectra of the remaining four…
Integral Field Spectroscopy of the Extended Emission-Line Region of 4C 37.43
Fu, Hai; Stockton, Alan
We present Gemini integral field spectroscopy and Keck II long-slit spectroscopy of the extended emission-line region (EELR) around the quasar 4C 37.43. The velocity structure of the ionized gas is complex and cannot be explained globally by a simple dynamical model. The spectra from the clouds are inconsistent with shock or ``shock + precursor'' …
The Nature of Optical Features in the Inner Region of the 3C 48 Host Galaxy
Fu, Hai; Stockton, Alan; Canalizo, Gabriela +1 more
The well-known quasar 3C 48 is the most powerful compact steep-spectrum radio-loud QSO at low redshifts. It also has two unusual optical features within the radius of the radio jet (~1"): (1) an anomalous, high-velocity narrow-line component, and (2) a bright continuum peak (3C 48A) ~1" northeast of the quasar. Both of these optical features have …
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…
VLT/near-infrared integral field spectrometer observations of molecular hydrogen lines in the knots of the planetary nebula NGC 7293 (the Helix Nebula)
Smith, M. D.; Zijlstra, A. A.; Lowe, K. T. E. +6 more
Knots are commonly found in nearby planetary nebulae (PNe) and star-forming regions. Within PNe, knots are often found to be associated with the brightest parts of the nebulae and understanding the physics involved in knots may reveal the processes dominating in PNe. As one of the closest PNe, the Helix Nebula (NGC 7293) is an ideal target to stud…
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 …
Colliding stellar wind models with non-equilibrium ionization: X-rays from WR 147
Zhekov, Svetozar A.
The effects of non-equilibrium ionization are explicitly taken into account in a numerical model which describes colliding stellar winds (CSW) in massive binary systems. This new model is used to analyse the most recent X-ray spectra of the WR+OB binary system WR 147. The basic result is that it can adequately reproduce the observed X-ray emission…