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Analysis of the Early Spectra and Light Curve of SN 1987A
Hauschildt, Peter H.; Ensman, Lisa M.
Numerical modeling of supernova spectra, light curves, and hydrodynamics requires physical inputs, numerical techniques, approximations, and assumptions which must be thoroughly understood in order to study the details of supernova explosions. Here, we discuss some of these in the context of the early evolution of supernova 1987A. Gray radiation-h…
Simultaneous Soft and Hard X-Ray Spectroscopy of AM Herculis with EXOSAT: Discovery of Photospheric Absorption Features
Paerels, Frits; van Teeseling, Andre; Heise, John
We present 0.1-10 keV spectroscopic observations of AM Herculis obtained with the Transmission Grating Spectrometers and Medium Energy experiments on EXOSAT, taken when the object was in its 'reversed X-ray mode.' The observation covers over six binary orbits without interruption, enabling us to analyze the phase and intensity dependence of both t…
On the Velocity Dispersion in the Core of the Globular Cluster M15
Meylan, G.; Mayor, M.; Dubath, P.
A projected velocity dispersion sigmap of 0 = 14.0 km/s is derived from an integrated light spectrum obtained at the European Southern Observatory (ESO) at La Silla, Chile, over a central 6 sec x 6 sec area in the core of the globular cluster M15. Extensive numerical simulations of velocity dispersion determinations from integrated ligh…
A Search for Chromospheric Emission in A-Type Stars Using the Goddard High-Resolution Spectrograph
Gilliland, Ronald L.; Simon, Theodore; Landsman, Wayne B.
We have used the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST) to search for chromospheric emission in the ultraviolet C II 1335 A lines of eight A-type stars. The B-V colors of these stars range from 0.12 to 0.22. We have detected emission in the spectrum of the A7 V star Altair, but in no other star. We present …
Spectral Variations in the Low-Mass X-Ray Binary 4U 0614+09
Singh, K. P.; Apparao, K. M. V.
We report the X-ray spectra of a binary 4U 0614+09 observed with EXOSAT on five different occasions in 1984 and 1986. In four observations in 1984, the source intensity was 'low' compared to its intensity in the 1986 observation. The source was steady on timescales of 10 to 1000 s in each of the 1984 observations but highly variable during the 198…
Far-Ultraviolet Imaging of the Globular Cluster NGC 6681 with WFPC2
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +13 more
We have imagined the globular cluster NGC 6681 in the far-UV and visible with Wide Field/Planetary Camera-2 (WFPC2) on the Hubble Space Telescope (HST). Our far-UV images show a sparsely populated and fully resolved central region, and we detect 122 stars. The far-UV to visible color-magnitude diagram shows a well-defined horizontal branch with no…
Hubble Space Telescope Fine Guidance Sensor Interferometric Observations of the Core of 30 Doradus
Lattanzi, M. G.; Bucciarelli, B.; Evans, I. N. +7 more
We present the results of the first high angular resolution observations taken with a Fine Guidance Sensor (FGS) aboard the Hubble Space Telescope (HST) of a star cluster embedded in very bright background. The strong and complex background around the R136 cluster in the 30 Dor nebula does not prevent the FGS from achieving performance close to it…
Generalized Spectral Model for 1--100 keV X-Ray Emission from Cygnus X-3 Based on EXOSAT Data
Singh, K. P.; Rao, A. R.; Chitnis, V. R. +1 more
The X-ray spectrum of the highly variable X-ray source, Cyg X-3, has so far defied a consistent explanation based on simple emission models. We have extracted two of the best data sets from the EXOSAT archives and performed a detailed spectral analysis for its 'high' and 'low' states. The analysis of the less frequently occurring 'low' state is pr…
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. II. SMP 85, A Young Planetary
Dopita, Michael A.; Ford, Holland C.; Maran, Stephen P. +6 more
We have obtained Hubble Space Telescope Planetary Camera images in the [O III] λ5007 A emission line, and FOS UV spectrophotometry of the low-excitation planetary nebula SMP 85 in the Large Magellanic Cloud. By combining these results with existing optical spectrophotometry, absolute flux measurements, and dynamical and density information, we hav…
Directivity of 100--500 keV Solar Flare Hard X-Ray Emission
Hurley, K.; Niel, M.; Li, P. +3 more
We have identified 28 solar flares simultaneously observed by a SIGNE detector aboard the Venera 13 and Venera 14 spacecraft and the Hard X-Ray Burst Spectrometer (HXRBS) aboard the Solar Maximum Mission (SMM), over a wide range of observing angles. Fourteen of them were also observed by the Gamma Ray Spectrometer (GRS) on SMM and were included in…