Search Publications
Optical Slitless Spectroscopy of Large Magellanic Cloud Planetary Nebulae: A Study of the Emission Lines and Morphology
Mutchler, Max; Blades, J. Chris; Balick, Bruce +3 more
Hubble Space Telescope Space Telescope Imaging Spectrograph slitless spectroscopy of LMC planetary nebulae (PNs) is the ideal tool to study their morphology and their ionization structures at once. We present the results from a group of 29 PNs that have been spatially resolved, for the first time, in all the major optical lines. Images in the ligh…
Discovery and Implications of a New Large-Scale Stellar Bar in NGC 5248
Laine, Seppo; Jogee, Shardha; Knapen, Johan H. +3 more
For decades, the grand-design SAB spiral galaxy NGC 5248 has been postulated to host a short bar of semimajor axis 22" (1.6 kpc). From dynamical and morphological arguments, however, we argue that its spiral structure is being driven by a large-scale bar whose corotation radius lies at ~115" (8.6 kpc). Our estimate is based partially on a deep R-b…
Hubble Space Telescope Imaging of a Peculiar Stellar Complex in NGC 6946
Elmegreen, Bruce G.; Hodge, Paul W.; Larsen, Søren S. +4 more
The stellar populations in a stellar complex in NGC 6946 are analyzed on images taken with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The complex is peculiar because of its very high density of stars and clusters and semicircular shape. Its physical dimensions are about the same as for the local Gould Belt, but the stel…
The Unusually Long Duration Gamma-Ray Burst GRB 000911: Discovery of the Afterglow and Host Galaxy
Axelrod, T. S.; Price, P. A.; Harrison, F. A. +18 more
Of all the well-localized gamma-ray bursts, GRB 000911 has the longest duration (T90=500 s) and ranks in the top 1% of BATSE bursts for fluence. Here we report the discovery of the afterglow of this unique burst. In order to simultaneously fit our radio and optical observations, we are required to invoke a model involving a hard electro…
Emergence and Drastic Breakdown of a Twisted Flux Rope to Trigger Strong Solar Flares in NOAA Active Region 9026
Kurokawa, Hiroki; Ishii, Takako T.; Wang, Tongjiang
An emerging twisted flux rope model to explain the drastic evolution of a flare-productive NOAA Active Region 9026 is presented. The drastic changes in the δ-type sunspot configuration were found to start shortly before the big flares of 2000 June 6: (1) rapid proper motions of sunspots started at the both sides of the central δ sunspot about 7 hr…
Very Large Telescope and Hubble Space Telescope Observations of the Host Galaxy of GRB 990705
Le Floc'h, E.; Sanders, D. B.; Mereghetti, S. +6 more
We present Very Large Telescope spectroscopic observations of the GRB 990705 host galaxy and highlight the benefits provided by the prompt phase features of gamma-ray bursts (GRBs) to derive the redshifts of the latter. In the host spectrum, we indeed detect an emission feature that we attribute to the [O II] λλ3726, 3729 doublet and derive an una…
Infrared Space Observatory Observations of the Unidentified 30 Micron Feature in Proto-Planetary Nebulae
Volk, Kevin; Kwok, Sun; Szczerba, Ryszard +1 more
The intrinsic emission profile of the unidentified broad 30 µm emission feature is derived from Infrared Space Observatory (ISO) spectra of proto-planetary nebulae (PPNs). The feature is resolved into two components: a narrower feature at 26 µm and a broader feature at 33 µm. The intrinsic profiles of these two features and their…
Flare- and Shock-accelerated Energetic Particles in the Solar Events of 2001 April 14 and 15
Cohen, C. M. S.; Maclennan, C. G.; Mason, G. M. +5 more
We report heavy-ion composition and spectra for the solar energetic particle (SEP) events of 2001 April 14 and 15, using the combined capabilities of the Advanced Composition Explorer (ACE), Wind, and the Interplanetary Monitoring Platform 8 (IMP-8) to cover the energy range from ~30 keV nucleon-1 to ~400 MeV nucleon-1. These…
Associated Absorption in Radio Quasars. I. C IV Absorption and the Growth of Radio Sources
Lehnert, Matthew D.; Athreya, Ramana M.; Saunders, Richard D. E. +4 more
We assess the global properties of associated C IV λλ1548, 1550 absorption lines measured in the spectra of radio-loud quasars drawn from a near-complete, low-frequency-selected sample. The observations span rest-frame C IV in two redshift ranges, 0.7<z<1.0 and 1.5<z<3.0, which were targeted in the UV with the Hubble Space Telescope Sp…
Variability of the Broad Balmer Emission Lines in 3C 390.3 from 1992 to 2000
Zheng, W.; Peterson, B. M.; Pronik, V. I. +2 more
We describe the results of an optical spectral monitoring campaign on the Seyfert galaxy 3C 390.3 carried out with a CCD spectrograph at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory in 1992-2000. Light curves for the Hα and Hβ emission lines and for the continuum in both the Hα and Hβ spectral regions are given. The lag betwe…