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The Late Afterglow and Host Galaxy of GRB 990712
Hjorth, Jens; Courbin, Frederic; Holland, Stephen +3 more
We present deep Hubble Space Telescope (HST) imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48-123 days after the burst occurred. The magnitudes of the host (R=21.9, V=22.5) and optical afterglow (R=25.4, V=…
Carbon and Hydrogen in Hot DB White Dwarfs
Vennes, Stéphane; Provencal, J. L.; Shipman, H. L. +1 more
The roles played by carbon and hydrogen in helium atmosphere (DB) white dwarf evolution is not well understood. We present GHRS observations (centered at 1215 and 1335 Å) of the hot helium white dwarfs PG 0112+104 (~30,000 K) and GD 190 (~23,000 K) and EUVE observations of the well-studied DB GD 358 (~27,000 K) and revisit pre-COSTAR observations …
Hubble Space Telescope NICMOS and WFPC2 Images of the HH 1 Jet: A Comparative Study
Bally, John; Rodríguez, Luis F.; Reipurth, Bo +2 more
We present new Hubble Space Telescope (HST) NICMOS images of the source region of the HH 1/2 flow. The HH 1 jet is traced in the [Fe II] 1.64 µm and the H2 2.12 µm lines to about 2.5" of the deeply embedded VLA source. In general, the structure of the jet is similar in H2 and [Fe II], with all the features having …
Cassini and Wind stereoscopic observations of Jovian nonthermal radio emissions: Measurement of beam widths
Gurnett, D. A.; Hospodarsky, G. B.; Kurth, W. S. +2 more
During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January the Jovian longitude difference between the two spacecraft was abou…
Polar Plumes and Inter-plume regions as observed by SUMER on SOHO
Doyle, J. G.; Teriaca, L.; Banerjee, D. +1 more
We present observations of O vi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R⊙ above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity a…
A Kinetic Model of Coronal Heating and Acceleration by Ion-Cyclotron Waves: Preliminary Results
Isenberg, Philip A.; Lee, Martin A.; Hollweg, Joseph V.
We present a kinetic model of the heating and acceleration of coronal protons by outward-propagating ion-cyclotron waves on open, radial magnetic flux tubes. In contrast to fluid models which typically insist on bi-Maxwellian distributions and which spread the wave energy and momentum over the entire proton population, this model follows the kinet…
Wide-Field J- and K-Band Galaxy Counts in the European Large-AreaInfrared Space Observatory Survey Fields
Willner, S. P.; Cohen, M.; Väisänen, P. +1 more
New near-infrared galaxy counts in the J and K bands are presented over a total area of 0.70 and 0.97 deg2, respectively. The limiting magnitudes of the deepest regions are 19.5 in J and 18.0 in K. At J>16 and K>15, our J- and K-band number counts agree well with existing surveys, provided that all data are corrected to a common m…
NICMOS Narrowband Infrared Photometry of TW Hydrae Association Stars
Kastner, Joel H.; Saumon, Didier; Forveille, Thierry +1 more
We have obtained 1.64, 1.90, and 2.15 µm narrowband images of five T Tauri stars in the TW Hya Association (TWA) using the Near-Infrared Camera and Multiobject Spectrometer aboard the Hubble Space Telescope. Most of the T Tauri stars in our study show evidence of absorption by H2O vapor in their atmospheres; in addition, the low-m…
Young massive star clusters in M51
Larsen, Søren S.
A search for young massive star clusters (YMCs) in the nearby face-on spiral galaxy M51 (NGC 5194) has been carried out using UBV CCD images from the prime focus camera on the Lick 3-m Shane telescope. The YMC population is found to be quite rich with a specific U-band luminosity TL(U)~1.4, consistent with the high current star formatio…
A multiwavelength view at the heart of the superwind in NGC253
Forbes, Duncan A.; Brodie, Jean P.; Stevens, Ian R. +2 more
Although NGC253 is one of the nearest starburst galaxies, the activity in its central regions is yet to be fully understood. Here we present new optical data from the Hubble Space Telescope of its central region, which reveal numerous discrete sources in a ring-like structure. This is combined with data at infrared, millimetre, radio and X-ray wav…