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LBQS 0103-2753: A 0.3" Binary Quasar
Burbidge, E. M.; Junkkarinen, V.; Shields, G. A. +4 more
Imaging and spectroscopy with the Hubble Space Telescope show that LBQS 0103-2753 (V=17.8, z=0.848) is a binary quasar with a separation of 0.3", or 2.3 kpc. This is by far the smallest separation binary quasar reported to date. The two components have very different spectra, including the presence of strong broad absorption lines (BALs) in compon…
Tailored Analyses of the WN 8 Stars WR 40 and WR 16
Hillier, D. J.; Herald, J. E.; Schulte-Ladbeck, R. E.
We present the results of tailored spectral analyses of two WN 8 Wolf-Rayet stars: WR 40 (HD 96548) and WR 16 (HD 86161). These analyses were carried out utilizing line-blanketed non-LTE model atmospheres with provisions for a clumped wind. For the first time in WN analyses, stellar parameters are derived by attempting to match the entire observed…
Why Are Solar Filaments More Extended in Extreme-Ultraviolet Lines than in Hα?
Heinzel, P.; Schmieder, B.; Tziotziou, K.
A long solar filament was observed simultaneously in the Hα line by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic Spectrometer on SOHO. Co-alignment of optical and EUV images reveals that the dark EUV filament is much more extended than the Hα filament. Assuming that the EUV filament represents Lyman continuum absorption of the b…
Imaging an Emerging Active Region with Helioseismic Tomography
Christensen-Dalsgaard, Jørgen; Duvall, Thomas L., Jr.; Jensen, Jesper Munk +1 more
The wave-speed structure beneath an emerging active region is derived from helioseismic time-distance data using inversion techniques developed in geophysics. We use Fresnel zone-based sensitivity kernels along with a Fourier domain-based regularized least-squares inversion technique. The results show that wave-speed anomalies extend down to 20 Mm…
The Discovery of Cepheids and a New Distance to NGC 2841 Using the Hubble Space Telescope
Garnavich, P. M.; Richmond, M. W.; Stetson, P. B. +5 more
We report on the discovery of Cepheids in the spiral galaxy NGC 2841, based on observations made with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. NGC 2841 was observed over 12 epochs using the F555W filter and over five epochs using the F814W filter. Photometry was performed using the DAOPHOT/ALLFRAME package. We discove…
The Crab Nebula's Moving Wisps in Radio
Frail, D. A.; Hester, J. J.; Bietenholz, M. F.
We present three high-resolution radio images of the Crab Nebula, taken in 1998.6, 1998.8, and 2000.1 with the VLA. These are the best radio images of the Crab to date. We show that, near the pulsar, there are significant changes between our three observing epochs. These changes have an elliptical geometry very similar to that of the optical wisps…
Spatially Resolved O II Recombination Line Observations of the Ring Nebula, NGC 6720
Garnett, Donald R.; Dinerstein, Harriet L.
We present new long-slit CCD spectra of O II permitted lines and [O III] forbidden lines in the Ring Nebula NGC 6720. These observations provide spatially resolved information on both O II and [O III] over the 70" diameter of the main shell. We find significant differences in the spatial distribution of the O II lines and [O III] λ4959. The [O III…
The Intrinsic Absorber in QSO 2359-1241: Keck and HUBBLE SPACE TELESCOPE Observations
White, Richard L.; Gregg, Michael D.; Becker, Robert H. +4 more
We present detailed analyses of the absorption spectrum seen in QSO 2359-1241 (NVSS J235953-124148). Keck HIRES data reveal absorption from 20 transitions arising from He I, Mg I, Mg II, Ca II, and Fe II. Hubble Space Telescope data show broad absorption lines (BALs) from Al III λ1857, C IV λ1549, Si IV λ1397, and N V λ1240. Absorption from excite…
GRB 000418: A Hidden Jet Revealed
Berger, E.; Bloom, J. S.; Cline, T. +15 more
We report on optical, near-infrared, and centimeter radio observations of GRB 000418 that allow us to follow the evolution of the afterglow from 2 to 200 days after the γ-ray burst (GRB). In modeling these broadband data, we find that an isotropic explosion in a constant-density medium is unable to simultaneously fit both the radio and optical dat…
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Arakelian 564. II. Ultraviolet Continuum and Emission-Line Variability
Brandt, W. N.; Clavel, J.; Kriss, G. A. +15 more
We present results of an intensive 2 month campaign of approximately daily spectrophotometric monitoring of the narrow-line Seyfert 1 galaxy (NLS1) Ark 564 with the Hubble Space Telescope. The fractional variability amplitude of the continuum variations between 1365 and 3000 Å is ~6%, about a factor of 3 less than that found in typical Seyfert 1 g…