Search Publications
Formation of Minor-Ion Charge States in the Fast Solar Wind: Roles of Differential Flow Speeds of Ions of the Same Element
Chen, Y.; Hu, Y.; Esser, R.
To investigate the possibility of differential flow speeds between ions of the same element and their roles in the determination of ionic fractions, this paper extends our latest minor-ion model to a five-fluid model, describing the behavior of five species of minor ions of one given element in the fast solar wind. We solve the five sets of mass, …
Using Multiwavelength Observations to Determine the Black Hole Mass and Accretion Rate in the Type 1 Seyfert Galaxy NGC 5548
Chiang, James; Blaes, Omer
We model the spectral energy distribution of the type 1 Seyfert galaxy NGC 5548, fitting data from simultaneous optical, UV, and X-ray monitoring observations. We assume a geometry consisting of a hot central Comptonizing region surrounded by a thin accretion disk. The properties of the disk and the hot central region are determined by the feedbac…
A Method for Black Hole Mass Determination in Accretion-powered X-Ray Sources
Titarchuk, Lev; Shrader, Chris R.
We describe a method for the determination of black hole masses based on information inferred from high-energy spectra. It is required that the spectral energy distribution consist of thermal and Comptonized components. One can then, in principle, infer the depth of the gravitational potential well for sources of known distance. The thermal compon…
GRB 010921: Strong Limits on an Underlying Supernova from the Hubble Space Telescope
Piro, L.; Axelrod, T. S.; Frontera, F. +24 more
GRB 010921 was the first HETE-2 gamma-ray burst (GRB) to be localized via its afterglow emission. The low redshift of the host galaxy, z=0.451, prompted us to undertake intensive multicolor observations with the Hubble Space Telescope with the goal of searching for an underlying supernova (SN) component. We do not detect any coincident SN to a lim…
Probing the Size of Low-Redshift Lyα Absorbers
Stocke, John T.; Giroux, Mark L.; Ganguly, Rajib +1 more
The 3C 273 and RX J1230.8+0115 sight lines probe the outskirts of the Virgo Cluster at physical separations between the sight lines of 200 and 500 h-170 kpc. We present an analysis of available Hubble Space Telescope STIS echelle and Far-Ultraviolet Spectroscopic Explorer (FUSE) UV spectroscopy of RX J1230.8+0115, in which we…
Stellar Hydrodynamics in Radiative Regions
Rigby, Jane R.; Knierman, Karen A.; Young, Patrick A. +1 more
We present an analysis of the response of a radiative region to waves generated by a convective region of the star; this wave treatment of the classical problem of ``overshooting'' gives extra mixing relative to the treatment traditionally used in stellar evolutionary codes. The interface between convectively stable and unstable regions is dynamic…
The Homogeneity of Interstellar Krypton in the Galactic Disk
Meyer, David M.; Cartledge, Stefan I. B.; Lauroesch, J. T.
We present an analysis of high-resolution Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of Kr I λ1236 absorption in seven sight lines that probe a variety of interstellar environments. In combination with krypton and hydrogen column densities derived from current and archival STIS and Far-Ultraviolet Spectroscopic…
Temporal Evolution of a Streamer Complex: Coronal and in Situ Plasma Parameters
Parenti, S.; Romoli, M.; Riley, P. +5 more
We report on observations acquired by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO), from 2000 June 10 to June 17 at the time of a SOHO-Sun-Ulysses quadrature. UVCS took data at 1.6 and 1.9 Rsolar with a slit normal to the solar radius and centered along the radial to Ulysses. A str…
Detection of Pulsed X-Ray Emission from XMM-Newton Observations of PSR J0538+2817
Cropper, M.; McGowan, K. E.; Kennea, J. A. +5 more
We report on the XMM-Newton observations of the 143 ms pulsar PSR J0538+2817. We present evidence for the first detections of pulsed X-rays from the source at a frequency that is consistent with the predicted radio frequency. The pulse profile is broad and asymmetric, with a pulse fraction of 18%+/-3%. We find that the spectrum of the source is we…
Galaxies under the Cosmic Microscope: A Gemini Multiobject Spectrograph Study of Lensed Disk Galaxy 289 in A2218
Smail, I.; Kneib, J. -P.; Smith, Graham P. +7 more
In this paper, we exploit the gravitational potential of the rich cluster A2218 as a magnifying glass. We demonstrate that the magnification due to the cluster allows us to observe distant background galaxies at a comparable level of detail to galaxies at z~0.1. Using the Gemini Multiobject Spectrograph (GMOS) integral field unit (IFU) on Gemini N…