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LBDS 53W091: An Old, Red Galaxy at z = 1.552
Windhorst, Rogier; Dey, Arjun; Spinrad, Hyron +4 more
The weak radio source LBDS 53W091 is associated with a very faint (R ~ 24.5) red (R - K ~ 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an absorption-line redshift, z = 1.552 +/- 0.002. The galaxy has a rest frame ultraviolet spectrum very similar to that of an F6 V star, and a single-burst old stellar po…
Synthetic Spectra of Hydrodynamic Models of Type Ia Supernovae
Baron, E.; Branch, David; Hauschildt, Peter H. +2 more
We present detailed non-LTE synthetic spectra of hydrodynamic supernovae (SNe) Ia models. We make no assumptions about the form of the spectrum at the inner boundary. We calculate both Chandrasekhar-mass deflagration models and sub-Chandrasekhar ``helium detonators.'' Gamma-ray deposition is handled in a simple, accurate manner. We have parameteri…
Self-consistent Thermal Accretion Disk Corona Models for Compact Objects. II. Application to Cygnus X-1
Begelman, Mitchell C.; Wilms, Joern; Dove, James B. +1 more
We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broadband X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper, models in which the Comptonizing medium is a slab surrounding the cold accretion disk cannot have a temperature higher than about 140 keV for optical d…
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304 in 1994 May. III. Probing the Inner Jet through Multiwavelength Correlations
Shull, J. M.; Takahashi, T.; Urry, C. Megan +16 more
In 1994 May, the BL Lac object PKS 2155-304 was observed continuously for ~10 days with the International Ultraviolet Explorer and the Extreme Ultraviolet Explorer and for 2 days with ASCA, as well as with ROSAT and with ground-based radio, infrared, and optical telescopes. The light curves show a well-defined X-ray flare followed by a broader, lo…
Multiwavelength Observations of 3C 273 in 1993-1995
McHardy, I.; Ghisellini, G.; McBreen, B. +30 more
We present the results of the multiwavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993, this quasar showed an increase of its flux for energies >=100 MeV from about 2.1 × 10-7 photons cm-2 s-1 to approximately 5.6 × 10-7 photons cm-2 s-1 during a rad…
Nuclear Spiral and Ring Star-forming Structures and the Starburst--Active Galactic Nucleus Connection in Barred Spirals NGC 3351 and NGC 4303
Colina, Luis; Alberdi, A.; Krabbe, A. +2 more
A high-resolution Hubble Space Telescope WFPC2 F218W UV image of the barred spiral NGC 4303 (classified as a LINER-type active galactic nucleus [AGN]) reveals for the first time the existence of a nuclear spiral structure of massive star-forming regions all the way down to the UV-bright unresolved core (size <= 8 pc) of an active galaxy.
T…The Star-grazing Extrasolar Comets in the HD 100546 System
Sitko, M. L.; Grady, C. A.; Bjorkman, Karen S. +4 more
Redshifted absorption profiles that resemble the high-velocity circumstellar gas features in the spectrum of β Pictoris have been detected in IUE data for the 10 Myr old Herbig Be star, HD 100546, on 1995 March 7. In addition to Mg II, Si II, and other refractory species similar to those seen in β Pic, the HD 100546 spectra are rich in accreting g…
A Hubble Space Telescope Faint Object Spectrograph Survey for Broad Absorption Lines in a Sample of Low-redshift Weak [O III] Quasi-stellar Objects
Turnshek, David A.; Espey, Brian R.; Monier, Eric M. +1 more
The study by Boroson & Meyers led to the suggestion that radio-quiet QSOs with weak [O III] and strong Fe II emission spectra form a class of QSOs that has a high probability of exhibiting broad absorption lines (BALs) in their spectra. Furthermore, they argued that since narrow-line [O III] emission is almost certainly emitted isotropically, …
Detailed Non-LTE Model Atmospheres for Novae during Outburst. I. New Theoretical Results
Baron, E.; Shore, Steven N.; Hauschildt, Peter H. +3 more
We present new, detailed non-LTE (NLTE) calculations for model atmospheres of novae during outburst. This fully self-consistent NLTE treatment for a number of model atoms includes 3922 NLTE levels and 47,061 NLTE primary transitions. We discuss the implication of departures from LTE for the strengths of the lines in nova spectra. The new results s…
High-Resolution Ultraviolet Observations of the Highly Ionized Interstellar Gas toward Radio Loops I and IV
Tripp, Todd M.; Sembach, Kenneth R.; Savage, Blair D.
We present new Goddard High-Resolution Spectrograph (GHRS) echelle observations of the high ionization lines of Si IV, C IV, and N V toward HD 119608, a halo star at d = 4.1 kpc behind the Loop I and IV supernova remnants. Absorption along the path to HD 119608 makes it possible to study energetic processes that may result in the flow of gas into …