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X-ray spectral variability of the Seyfert galaxy NGC 4593.

Ghosh, K. K.; Soundarajaperumal, S.

X-ray (0.1-10 keV) spectra of NGC 4593 were obtained with EXOSAT on seven epochs between 1984 and 1986 using the low and medium energy detectors. Detailed results of the spectral analysis of the seven spectra (obtained from the EXOSAT database) of this galaxy are presented here. Power-law, two power-law, thermal bremsstrahlung and broken power- la…

The Spectral Form and Evolution of Interplanetary Ion Events from Jupiter

Simnett, G. M.; Krimigis, S. M.; Tappin, S. J. +4 more

Evidence for accelerated electrons upstream from Jupiter's bow shock: Ulysses results

Chaizy, P.; Anderson, K. A.; Lin, R. P. +1 more

Several transient increases of electrons with energies in the range 40-100 keV have been detected upstream and immediately downstream from the Jovian bow shock (and only in these regions), by instruments on the Ulysses spacecraft during February 1992. The energy spectra of these electrons differ markedly from the energy spectrum of the trapped mag…

Hubble Space Telescope Observations of the Center of Globular Cluster M15

Yanny, Brian

Images of the dense center of globular cluster M15 (NGC 7078) have been obtained with the Hubble Space Telescope in the V and I filters. Accurate photometry is possible in the very densest part of the cluster center with rms errors of <0.3 magnitudes for stars down to the main sequence turnoff. Evidence for radial segregation between horizontal…

The Ulysses encounter with Jupiter: an introduction

Smith, Edward J.; Wenzel, Klaus-Peter

Goddard High-Resolution Spectrograph Observations of Narrow Discrete Stellar Wind Absorption Features in the Ultraviolet Spectrum of the O7.5 III Star XI Persei

Ebbets, Dennis C.; Bolton, C. T.; Shore, Steven N. +2 more

We report the observation of transient narrow absorption components (NACs) in the stellar wind of the O giant Xi Per. Two sets of GHRS observations of the Si IV ultraviolet resonance doublet have been obtained. These features are extremely weak, with column densities of approximately 10 exp 12/sq cm and optical depths of order 0.1. The features ar…

The star-formation history of GR8 with HST imagery.

Dufour, R. J.; Wyatt, R. J.

The authors report the results of a deep imaging study of the nearby irregular galaxy GR8 using the Wide-Field Camera on the Hubble Space Telescope. These data enable them to perform photometry on stars as faint as R ≡ 24.5 with spatial resolution superior to ground-based observations. Color-magnitude diagrams in the "BVR" filters are presented an…

Structure, motion, and composition of the Orion Nebula.

O'Dell, C. R.

The author reviews the large scale structure of the Orion Nebula, incorporating recent results from 21 cm absorption studies, optical emission line investigations, and Hubble Space Telescope imaging. The ionization structure at the brightest ionization front is clearly defined and demonstrates a well organized flow away from the front. The ionized…

Are PSR 0656+14, PSR 0950+08, and PSR 1822-09 gamma-ray pulsars?

Brown, Lawrence E.; Hartmann, Dieter H.

The possible discovery of three new γ-ray pulsars PSR 0656+14, PSR 0950+08, and PSR 1822-09 (Ma, Lu, Yu, and Young, 1993) in data obtained with the COS-B experiment is reinvestigated using a refined technique for pulsar light curve analysis. The results of this study do not confirm the previously claimed γ-ray pulsar nature of any of these pulsars…

Effect of interstellar absorption on the MG II H & K profiles and fluxes of RS CVn stars

Doyle, J. G.; Houdebine, E. R.; Butler, C. J.