Search Publications
A Remarkable Auroral Event on Jupiter Observed in the Ultraviolet with the Hubble Space Telescope
Paresce, F.; Waite, J. H.; Grodent, D. +7 more
Two sets of ultraviolet images of the Jovian north aurora were obtained with the Faint Object Camera on board the Hubble Space Telescope. The first series shows an intense discrete arc in near corotation with the planet. The maximum apparent molecular hydrogen emission rate corresponds to an electron precipitation of ~1 watt per square meter, whic…
The spectrum of the planetary nebula NGC 6572.
Feibelman, W. A.; Hyung, S.; Aller, L. H.
A detailed, high-spectral-resolution study of the spectrum of the planetary nebula NGC 6572 is made for the optical region 365 to 1005 nm, using the Hamilton echelle spectrograph of Lick Observatory, and for the ultraviolet (UV) spectral region 125 to 320 rIm with the high-dispersion mode of the International Ultraviolet Explorer (lUE) satellite. …
GHRS Observations of Cool, Low-Gravity Stars. I. The Far-Ultraviolet Spectrum of alpha Orionis (M2 Iab)
Brown, Alexander; Robinson, Richard D.; Linsky, Jeffrey L. +2 more
We present far-UV (1200-1930 A) observations of the prototypical red supergiant star alpha Ori, obtained with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). The observations, obtained in both low- (G140L) and medium- (G160/200M) resolution modes, unambiguously confirm that the UV 'continuum' tentatively seen w…
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…
Absolute Flux Calibration of Optical Spectrophotometric Standard Stars
Colina, L.; Bohlin, R. C.
A method based on Landolt photometry in B and V is developed to correct for a wavelength independent offset of the absolute flux level of optical spectrophotometric standards. The method is based on synthetic photometry techniques in B and V and is accurate to approximately 1%. The correction method is verified by Hubble Space Telescope Faint Obje…
The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive
Giommi, Paolo; Barr, Paul; Sambruna, Rita M. +3 more
We analyzed the 0.1-10 keV spectra of 26 blazars (21 BL Lac objects and 5 highly polarized quasars), on the basis of 93 exposures taken from the EXOSAT archives. Fits were performed first with a single power-law model. Indications are found that better fits can be obtained with models where the slope steepens at higher energies. We therefore consi…
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 …
Effects of spacecraft potential on three-dimensional electron measurements in the solar wind
Scime, Earl E.; Bame, Samuel J.; Phillips, John L.
Using the three-dimensional, low-energy electron spectrometer aboard the Ulysses spacecraft, we have measured the gyrotropicity of electron distributions in the solar wind. In order to make these observations, we have developed a new technique for correcting spacecraft charging effects in three-dimensional, low-energy particle measurements. Compar…
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…