Search Publications
Proper Motion of the Sagittarius Dwarf Galaxy Based on Hubble Space Telescope Imaging
Piatek, Slawomir; Pryor, Carlton; Olszewski, Edward W.
We have derived a proper motion of Sagittarius using archival data obtained with the Hubble Space Telescope. The data consist of imaging at three epochs with a time baseline of about four years in three distinct fields. The zero point for the proper motion is based on the foreground Galactic stellar populations along the line of sight. The measure…
Detection of Free Unstable Modes and Massive Bodies in Saturn's Outer B Ring
Porco, C. C.; Spitale, J. N.
Voyager images and Cassini occultation data have previously shown that the behavior of the outer edge of Saturn's massive B ring is determined only in part by a static response to the 2:1 inner Lindblad resonance with Mimas. In Cassini images of this region, we find, in addition to the expected wavenumber-2 forced distortion, evidence for unforced…
The Star Cluster Population of the Collisional Ring Galaxy NGC 922
Knezek, Patricia M.; Meurer, Gerhardt R.; Elmegreen, Debra M. +3 more
We present a detailed study of the star cluster population detected in the galaxy NGC 922, one of the closest collisional ring galaxies known to date, using Hubble Space Telescope/Wide Field Planetary Camera 2 UBVI photometry, population synthesis models, and N-body/smoothed particle hydrodynamics simulations. We find that 69% of the clusters are …
The Architecture of the Cassini Division
Sotin, C.; Brown, R. H.; Baines, K. H. +6 more
The Cassini Division in Saturn's rings contains a series of eight named gaps, three of which contain dense ringlets. Observations of stellar occultations by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft have yielded ~40 accurate and precise measurements of the radial position of the edges of all of these gaps and ring…
Hard X-ray Emission Associated with White Dwarfs. III.
Chu, You-Hua; Bilíková, Jana; Gruendl, Robert A. +1 more
Hard X-ray emission associated with white dwarfs (WDs) can be used to diagnose the presence of late-type binary companions, mass accretion from companions, or physical processes with unknown origins. Since our previous systematic searches for hard X-ray emission associated with WDs, the Galactic WD catalog has been augmented by >10,000 new WDs …
Hubble Space Telescope Spectrophotometry and Models for Solar Analogs
Bohlin, R. C.
Absolute flux distributions for seven solar analog stars are measured from 0.3 to 2.5 µm by Hubble Space Telescope (HST) spectrophotometry. In order to predict the longer wavelength mid-IR fluxes that are required for James Webb Space Telescope calibration, the HST spectral energy distributions are fit with Castelli & Kurucz model atmosp…
Spectral Irradiance Calibration in the Infrared. XVII. Zero-magnitude Broadband Flux Reference for Visible-to-infrared Photometry
Kraemer, Kathleen E.; Price, Stephan D.; Engelke, Charles W.
The absolutely calibrated infrared (IR) stellar spectra of standard stars described by Engelke et al. are being extended into the visible and will span a continuous wavelength range from ~0.35 µm to 35.0 µm. This paper, which is a continuation of the series on calibration initiated with Cohen et al., presents the foundation of this ext…
Spectroscopy of M81 Globular Clusters
Nantais, Julie B.; Huchra, John P.
We obtained spectra of 74 globular clusters (GCs) in M81. These GCs had been identified as candidates in a Hubble Space Telescope (HST) Advanced Camera for Surveys I-band survey. Sixty-eight of these 74 clusters lie within 7' of the M81 nucleus. Sixty-two of these clusters are newly spectroscopically confirmed, more than doubling the number of con…
The Hα Variations of η Carinae During the 2009.0 Spectroscopic Event
Okazaki, A. T.; Fernández-Lajús, E.; Gies, D. R. +2 more
We report on Hα spectroscopy of the 2009.0 spectroscopic event of η Carinae collected via SMARTS observations using the Cerro Tololo Interamerican Observatory 1.5 m telescope and echelle spectrograph. Our observations were made almost every night over a two-month interval around the predicted minimum of η Car. We observed a significant fading of t…
Combined Analysis of Images and Spectral Energy Distributions of Taurus Protostars
Whitney, Barbara A.; Gramajo, Luciana V.; Gómez, Mercedes +1 more
We present an analysis of spectral energy distributions (SEDs), near- and mid-infrared images, and Spitzer spectra of eight embedded Class I/II objects in the Taurus-Auriga molecular cloud. The initial model for each source was chosen using the grid of young stellar objects (YSOs) and SED fitting tool of Robitaille et al. Then the models were refi…