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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 …
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…
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. I. The Nature of the Continuum Emission
Crenshaw, D. Michael; Kraemer, Steven B.
We present the first long-slit spectra of the Seyfert 2 galaxy NGC 1068 obtained by the Space Telescope Imaging Spectrograph (STIS) the spectra cover the wavelength range 1150-10270 Å at a spatial resolution of 0.05"-0.1" and a spectral resolving power of λ/Δλ~1000. In this first paper, we concentrate on the far-UV to near-IR continuum emission fr…
Recent Changes in the Near-Infrared Structure of η Carinae
Smith, Nathan; Gehrz, Robert D.
Near-infrared imaging at two phases in the 5 yr spectroscopic cycle of η Carinae reveals changes in the spatial structure of the inner core that may be related to recently reported near-infrared photometric variability. The central source changed from a pointlike object to a more extended, bipolar or shell structure. This behavior is reminiscent o…
Radio Tracking of a White-Light Coronal Mass Ejection from Solar Corona to Interplanetary Medium
Plunkett, S. P.; Kaiser, M. L.; Reiner, M. J. +2 more
For a solar flare/coronal mass ejection (CME) event on 1999 May 3, type II radio emissions were observed from the metric through the hectometric wavelength regimes. By comparing the dynamics of the CME with that implied by the frequency range and frequency drift rates of the type II radio emissions, it is concluded that the decametric-hectometric …
Space Telescope Imaging Spectrograph Echelle Observations of NGC 4151: Variable Ionization of the Intrinsic UV Absorbers
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +5 more
We present echelle observations of the intrinsic UV absorption lines in the Seyfert galaxy NGC 4151; these observations were obtained with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope on 1999 July 19. The UV-continuum flux at 1450 Å decreased by factor of about 4 over the previous 2 years, and there was a correspondin…
High-Resolution Infrared Imaging of the Compact Nuclear Source in NGC 4258
Chary, R.; Scoville, N. Z.; Matthews, K. +4 more
We present high-resolution imaging of the nucleus of NGC 4258 from 1 to 18 µm. Our observations reveal that the previously discovered compact source of emission is unresolved even at the near-infrared resolution of ~0.2" FWHM, which corresponds to about 7 pc at the distance of the galaxy. This is consistent with the source of emission being …
Hubble Space Telescope Observations and Photoionization Modeling of the LINER Galaxy NGC 1052
Kraemer, S. B.; Crenshaw, D. M.; Bruhweiler, F. C. +2 more
We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observations of the low-ionization nuclear emission-line region (LINER) galaxy NGC 1052. The WFPC2 imagery clearly differentiates extended nebular Hα emission from that of the compact core. Faint Object Spectrograph (FOS) observations provide a full set of optic…