Search Publications
A Dwarf Nova in the Core of 47 Tucanae
Paresce, Francesco; de Marchi, Guido
The Faint Object Camera on the Hubble Space Telescope detected an outburst of a star (V2) located in the core of the Galactic globular cluster 47 Tucanae that occured in 1993 October. The instrumental magnitudes at 220 and 342 nm at outburst were 15.4 and 16.2, respectively. Observations of the same object made a year before and 2 weeks later gave…
IUE Spectra and Photoionization Models of the Seyfert 2 Galaxies NGC 7674 and I ZW 92
Crenshaw, D. Michael; Wu, Chi-Chao; Harrington, J. Patrick +1 more
The physical conditions in the narrow-line regions of two Seyfert 2 galaxies, NGC 7674 and I Zw 92, are examined using IUE spectra, published optical spectra and multifrequency observations, and photoionization models. For each Seyfert galaxy, the emission-line fluxes were dereddened using the He II λ1640/λ4686 ratio. Photoionization models were c…
A Hubble Space Telescope Ultraviolet Spectrum of SN 1993J
Filippenko, Alexei V.; Pun, Chun S. J.; Fransson, Claes +10 more
We obtained a Hubble Space Telescope ultraviolet spectrum of the Type II supernova SN 1993J in M81 on 1993 April 15. The ~1650-2900 A region is smoother than observed for SN 1987A and SN 1992A and lacks strong P Cygni absorptions caused by iron peak element lines. Synthetic spectra calculated using a parameterized LTE procedure and a simple model …
Modeling and Interpretation of the Optical and HST UV Spectrum of SN 1993J
Hauschildt, P. H.; Baron, E.; Branch, D.
We present spherically symmetric, non-LTE, expanding model atmosphere synthetic spectra of SN 1993J and compare them to the ultraviolet and optical spectra obtained simultaneously on 1993 April 15 by the HST and at Lick Observatory. We are able to fit the optical and HST near-UV spectra with a variety of compositions, but find that our best fits a…
A Large, Periodic Variation in the Stellar Wind of theta 1 Orionis C
Walborn, Nolan R.; Nichols, Joy S.
A period of 15.4 days, recently discovered by Stahl et al. from intensive monitoring of hydrogen alpha emission in Theta1 Ori C during 1992-1993, has been found to phase large variations in the C IV lambda lambda 1548, 1551 wind profile of this star previously reported from International Ultraviolet Explorer (IUE) high-resolution data o…
Hubble Space Telescope Imaging of the Seyfert 2 Galaxy NGC 2110
Heckman, Timothy M.; Mulchaey, John S.; Bower, Gary A. +3 more
Hubble Space Telescope (HST) images of the Seyfert 2 galaxy NGC 2110 in the emission lines of [O III] λλ4959,5007 and Hα + [N II] λλ6548,6584 and the nearby continuum are presented. After deconvolution, the resolution of these images is ~0.1", corresponding to a linear scale of ~23 pc at the assumed distance (46.8 Mpc) to this galaxy. The dominant…
Cooling of the White Dwarf in U Geminorum between Outbursts
Szkody, Paula; Sion, Edward M.; Long, Knox S. +1 more
We have obtained far-ultraviolet (1150-1610 A) spectra of U Gem with the Faint Object Spectrograph on the Hubble Space Telescope approximately 13 and 70 days after the end of a normal dwarf nova outburst of the system. Both spectra appear dominated by the White Dwarf (WD) in U Gem. At 1400 A, the flux from U Gem declined approximately 28% between …
Multiwavelength Study of the Magnetically Active T Tauri Star HD 283447
Feigelson, Eric D.; Phillips, Robert B.; Imhoff, Catherine +4 more
We observed the luminous T Tauri star HD 283447 = V773 Tauri simultaneously at X-ray, ultraviolet, optical photometric and spectroscopic, and radio wavelengths for several hours on UT 1992 September 11. ROSAT, IUE, Very Large Array (VLA) and an intercontinental Very Long Baseline Interferometry (VLBI) network, and three optical observatories parti…
Galaxy Mergers and Gravitational Lens Statistics
Maoz, Dan; Rix, Hans-Walter; Turner, Edwin L. +1 more
We investigate the impact of hierarchical galaxy merging on the statistics of gravitational lensing of distant sources. Since no definite theoretical predictions for the merging history of luminous galaxies exist, we adopt a parameterized prescription, which allows us to adjust the expected number of pieces comprising a typical present galaxy at z…
Highly Ionized Gas Absorption in the Disk and Halo toward HD 167756 at 3.5 Kilometers per Second Resolution
Sembach, Kenneth R.; Savage, Blair D.; Cardelli, Jason A.
High-resolution spectra of interstellar Si IV, C IV, and N V absorption lines along the 4 kpc path to the inner Galaxy star HD 167756 at z = -0.85 kpc are presented. The spectra were obtained with the echelle mode of Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST) and have signal-to-noise ratios ranging from 23 …