Search Publications
A Multiwavelength Campaign on γ Cassiopeiae. I. The Case for Surface X-Ray Flaring
Smith, Myron A.; Robinson, Richard D.; Corbet, Robin H. D.
In 1996 March we obtained simultaneous Rossi X-Ray Timing Explorer RXTE Proportional Counter Array (PCA) and Hubble Space Telescope (HST) Goddard High-Resolution Spectrograph (GHRS) light curves for the B0.5e star γ Cas in order to compare its X-ray and ultraviolet continuum flux behaviors. The GHRS data set consisted of a nearly continuous sequen…
Evolution of the Angular Correlation Function
Connolly, A. J.; Szalay, A. S.; Brunner, R. J.
For faint photometric surveys, our ability to quantify the clustering of galaxies has depended on interpreting the angular correlation function as a function of the limiting magnitude of the data. Because of the broad redshift distribution of galaxies at faint magnitude limits, the correlation signal has been extremely difficult to detect and inte…
Hubble Space Telescope Imaging of IRAS 17441-2411: A Case Study of a Bipolar Nebula with a Circumstellar Disk
Volk, Kevin; Kwok, Sun; Hrivnak, Bruce J. +1 more
The bipolar proto-planetary nebula IRAS 17441-2411 (the ``Silkworm Nebula'') was observed with the Hubble Space Telescope. By fitting the observed spectral energy distribution and the V-band image by a two-dimensional radiation transfer model, we derive the properties of the circumstellar wind and a proposed circumstellar ``disk.'' We suggest that…
2.12 Micron Molecular Hydrogen Emission from Circumstellar Disks Embedded in the Orion Nebula
Schneider, Glenn; Young, Erick T.; Rieke, Marcia +5 more
We present narrowband images of two externally illuminated circumstellar disks embedded in the Orion Nebula. The images were taken with camera 2 of the Near-Infrared Camera and Multiobject Spectrometer (NICMOS) as part of the Hubble Space Telescope Early Release Observations program. Molecular hydrogen emission is confined to the silhouettes embed…
The Adiabatic Exponent in the Solar Core
Kosovichev, A. G.; Elliott, J. R.
We present helioseismic inversions of solar p-mode frequencies obtained by the Michelson Doppler Imager instrument of the Solar Oscillation Investigation project on board SOHO, which indicate a lower central value for the adiabatic exponent Γ1 in the Sun than in current models. We show how the inclusion of relativistic effects in the eq…
Physical Structure of a Coronal Streamer in the Closed-Field Region as Observed from UVCS/SOHO and SXT/Yohkoh
Romoli, M.; Raymond, J. C.; Naletto, G. +4 more
We analyze a coronal helmet streamer observed on 1996 July 25 using instruments aboard two solar spacecraft, the Ultraviolet Coronagraph Spectrometer (UVCS) on board Solar and Heliospheric Observatory (SOHO) and the Soft X-Ray Telescope (SXT) on board Yohkoh. We derive temperatures and electron densities at 1.15 R⊙ from SXT/Yohkoh obser…
Deep H-Band Galaxy Counts and Half-Light Radii from Hubble Space Telescope/NICMOS Parallel Observations
McCarthy, Patrick J.; Weymann, Ray J.; Yan, Lin +1 more
We present deep galaxy counts and half-light radii from F160W (λc=1.6 µm) images obtained with the Near-Infrared Camera and Multiobject Spectrograph on the Hubble Space Telescope. Nearly 9 arcmin2 have been imaged with camera 3, with 3 σ depths ranging from H=24.3 to 25.5 in a 0.6" diameter aperture. The slope of the co…
Infrared Imaging and Spectroscopy of the Helix with ISOCAM
Boulanger, F.; Bachiller, R.; Cernicharo, J. +8 more
We report infrared images of the Helix Nebula centered at 6.9 µm (LW2 filter) and 15 µm (LW3 filter) obtained with ISOCAM on board the Infrared Space Observatory (ISO). Three fields were also measured using the ISOCAM circular variable filter (CVF). The CVF data show that the 5-16.6 µm spectrum is dominated by the pure (v=0-0) ro…
Optical and Near-Infrared Model Images of the Circumstellar Environments of Classical T Tauri Stars
Wood, Kenneth; Kenyon, Scott J.; Whitney, Barbara +1 more
We describe model calculations of optical and near-infrared scattered light images expected from class II T Tauri stars--the star-plus-disk systems. The parameters controlling the disk shape, size, and mass are chosen to be within theoretically and observationally derived limits. We restrict our models to nearly edge-on disks, since for lower incl…
Evidence for a 20 Parsec Disk at the Nucleus of Centaurus A
Marconi, Alessandro; Axon, David J.; Capetti, Alessandro +6 more
We report Hubble Space Telescope NICMOS observations of the central region of NGC 5128 at 2.2 µm and in Paα. The continuum images show extended emission typical of an elliptical galaxy and a strong unresolved central source we identify as the nucleus of the galaxy. Its position is consistent with ground-based IR and radio data, and with the …