Search Publications
Emission Line and Ultraviolet to X-Ray Continuum Correlations: Constraints on the Anisotropy of the Ionizing Continuum in Active Galactic Nuclei
Wang, Ting-Gui; Zhou, You-Yuan; Lu, You-Jun
Anisotropic emission of the ionizing continuum is a general prediction of accretion disk models. In this paper, we present the results of correlation analysis of the UV emission line and UV to X-ray continuum properties for a large sample of broad emission line AGNs observed with ROSAT, IUE, and HST. We find strong correlations between the C IV/Ly…
Hubble Space Telescope Imaging of the Circumstellar Nebulosity of T Tauri
Ballester, Gilda E.; Krist, John E.; Crisp, David +14 more
Short-exposure Planetary Camera images of T Tauri have been obtained using broadband filters spanning the wavelength range 0.55-0.80 µm. The optically visible star lies very close to an arc of reflection nebulosity. The arc's northern arm extends approximately 5" from the star, while its southwestern arm appears brighter and extends only 2".…
The Absolute Magnitude of RR Lyrae Stars Derived from the Hipparcos Catalogue
Yoshii, Yuzuru; Tsujimoto, Takuji; Miyamoto, Masanori
The present determination of the absolute magnitude MV(RR) of RR Lyrae stars is twofold, relying upon Hipparcos proper motions and trigonometric parallaxes separately. First, applying the statistical parallax method to the proper motions, we find V(RR)>=0.69+/-0.10 for 99 halo RR Lyrae stars with <[Fe/H>=-1.58. Second, applying…
The Host Galaxy of the Gamma-Ray Burst 971214
Piro, L.; Frontera, F.; Bloom, J. S. +13 more
We report on Hubble Space Telescope (HST) observations of the host galaxy of GRB 971214, taken 4 months after the burst. The redshift of the proposed host galaxy at z=3.418, combined with optical and radio observations of the burst afterglow, implies the extremely large isotropic energy release from the burst in γ-rays of Eγ~3×1053…
M87: A Misaligned BL Lacertae Object?
Kriss, Gerard A.; Dopita, Michael A.; Hartig, George F. +5 more
The nuclear region of M87 was observed with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) at six epochs, spanning 18 months, after the HST image quality was improved with the deployment of the corrective optics (COSTAR) in 1993 December. From the FOS target acquisition data, we have established that the flux from the opti…
Evidence for Strong and Weak Turbulence Processes in the Source Region of a Local Type III Radio Burst
MacDowall, R. J.; Thejappa, G.
We present the Ulysses Unified Radio and Plasma Wave Experiment (URAP) observations of a local type III radio burst and the associated plasma wave activity generated in the vicinity of the spacecraft. These observations represent the first clear evidence of (1) the occurrence of ion-acoustic waves as well as whistlers in close association with Lan…
Dissecting Capella's Corona: GHRS Spectra of the Fe XXI λ1354 and He II λ1640 Lines from Each of the Capella Stars
Brown, Alexander; Wood, Brian E.; Osten, Rachel A. +1 more
We report on moderate (λ/Δλ = 20,000) and high (λ/Δλ = 90,000) resolution spectra of the 104-day period Capella binary system (HD 34029) obtained with Hubble Space Telescope's Goddard High-Resolution Spectrometer (GHRS) on 1995 September 9 and 1996 April 9. The observations include a long-duration, moderate-resolution spectrum of the coronal Fe XX…
Radiative Transfer Models of Emission and Absorption in the H2O 6 Micron Vibration-Rotation Band toward Orion-BN-KL
Cernicharo, José; van Dishoeck, Ewine F.; Wright, Christopher M. +2 more
We report the spectrum of Orion-BN/KL between 5.3 and 7.2 µm observed with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. H2O lines of the ν2=1-0 bending mode with λ < 6.3 µm (the R-branch) are observed in absorption, while lines with λ > 6.3 µm (the P-branch) are obse…
Cosmological Parameters from Multiple-Arc Gravitational Lensing Systems. I. Smooth Lensing Potentials
Link, Robert; Pierce, Michael J.
We describe a new approach for the determination of cosmological parameters using gravitational lensing systems with multiple arcs. We exploit the fact that a given cluster can produce multiple arcs from sources over a broad range in redshift. The coupling between the critical radius of a single arc and the projected mass density of the lensing cl…
Seismic Holography of Solar Activity
Braun, D. C.; Lindsey, C.; Fan, Y. +1 more
Helioseismic images of sunspots show a remarkable acoustic anomaly surrounding the sunspot. We applied the computational formalism of ``helioseismic holography'' to SOHO-MDI observations to render acoustic images of NOAA AR 7973, an active region containing a moderately large sunspot. The results of this study are based on simple ``acoustic power …