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Observations of the Crab Nebula and Its Pulsar in the Far-Ultraviolet and in the Optical
Gull, Theodore R.; Pun, Chun S. J.; Fransson, Claes +5 more
We present far-UV observations of the Crab Nebula and its pulsar made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Broad, blueshifted absorption arising in the nebula is seen in C IV λ1550, reaching a blueward velocity of ~2500 km s-1. This can be interpreted as evidence for a fast outer shell surro…
A Coupled Model of Titan's Atmosphere and Ionosphere
Lara, L. M.; Rodrigo, R.; López-Moreno, J. J. +2 more
The paper deals with a coupled model of the upper atmosphere and ionosphere of Titan. The neutral atmosphere is described by a comprehensive photochemical model for 30° solar zenith angle with molecular and turbulent diffusive transport taken into account. At the upper boundary (1430 km) escaping flux of light molecules is included in boundary con…
N-Body Simulations of Compact Young Clusters near the Galactic Center
Lee, Hyung Mok; Figer, Donald F.; Kim, Sungsoo S. +1 more
We investigate the dynamical evolution of compact young star clusters (CYCs) near the Galactic center using Aarseth's Nbody6 codes. The relatively small number of stars in the cluster (5000-20,000) makes real-number N-body simulations for these clusters feasible on current workstations. Using Fokker-Planck (F-P) models, Kim, Morris, & Lee made…
High-Resolution Hubble Space Telescope STIS Spectra of C I and CO in theβ Pictoris Circumstellar Disk
Roberge, A.; Feldman, P. D.; Ferlet, R. +5 more
High-resolution far-ultraviolet (FUV) echelle spectra showing absorption features arising from C I and CO gas in the β Pic circumstellar (CS) disk were obtained on 1997 December 6 and 19 using the Space Telescope Imaging Spectrograph (STIS). An unsaturated spin-forbidden line of C I at 1613.376 Å not previously seen in spectra of β Pic was detecte…
The Halo Stars in NGC 5128. II. An Outer Halo Field and a New Metallicity Distribution
Harris, William E.; Harris, Gretchen L. H.
We present new Hubble Space Telescope WFPC2 (V, I) photometry for stars in NGC 5128 at a projected distance more than 30 kpc from the galaxy center. The color-magnitude diagram shows an old red-giant branch which is extremely broad in color, identical in its characteristics with our previously observed 20 kpc halo field (Harris et al.). To derive …
UBVRI and Hα Photometry of the Young Open Cluster NGC 6530
Bessell, Michael S.; Sung, Hwankyung; Chun, Moo-Young
New UBVRI and Hα photometry has been obtained for the young open cluster NGC 6530 located 10' east of the Lagoon Nebula (M8). We found 37 pre-main-sequence (PMS) stars with Hα emission and nine PMS candidates using the R-Hα color, a measure of Hα emission. From this new photometry we derived the cluster parameters (V0-MV=11.2…
Infrared Space Observatory Mid-Infrared Spectra of Reflection Nebulae
Werner, M. W.; Sellgren, K.; Uchida, K. I. +1 more
We present 5-15 µm imaging spectroscopy of the reflection nebulae vdB 17 (NGC 1333), vdB 59 (NGC 2068), vdB 101, vdB 111, vdB 133, and vdB 135, obtained with the infrared camera and circular variable filter wheel on the Infrared Space Observatory (ISO). These nebulae are illuminated by stars with Teff=3,600-19,000 K, implying UV (…
Solar and Heliospheric Observatory Observations of a Helical Coronal Mass Ejection
Thompson, B. J.; Raymond, J. C.; Ciaravella, A. +8 more
The EUV Imaging Telescope (EIT), Large Angle Spectrometric Coronagraph (LASCO), and Ultraviolet Coronagraph Spectrometer (UVCS) instruments aboard the SOHO satellite observed a prominence eruption (coronal mass ejection) on 1997 December 12. Ejected plasma moved at about 130 km s-1 in the plane of the sky and showed Doppler shifts betwe…
Modeling the motion and distribution of interstellar dust inside the heliosphere
Landgraf, M.
The interaction of dust grains originating from the local interstellar cloud with the environment inside the heliosphere is investigated. As a consequence of this interaction, the spatial distribution of interstellar dust grains changes with time. Since dust grains are charged in the interplanetary plasma and radiation environment, the interaction…
Revealing the Photodissociation Region: HST/NICMOS Imaging of NGC 7027
Bieging, John H.; Hora, Joseph L.; Dayal, Aditya +4 more
We report results from a Hubble Space Telescope (HST) and Near-Infrared Camera and Multiobject Spectrometer (NICMOS) program to study the distribution of hot neutral (molecular hydrogen) and ionized circumstellar material in the young planetary nebulae NGC 7027. HST/NICMOS provided very high spatial resolution imaging in line and continuum emissio…