Search Publications
Vesta: Spin Pole, Size, and Shape from HST Images
Storrs, Alex D.; Thomas, Peter C.; Binzel, Richard P. +3 more
HST images obtained over an interval of 71 hr at a scale of 52 km/pixel have been used to determine the spin pole, size, and shape of Vesta. Several bright and dark surface features allow control point stereogrammetric measurement of spin pole orientation. An independent solution of spin pole and shape can be made from the limb and terminator coor…
Self-consistent Thermal Accretion Disk Corona Models for Compact Objects. II. Application to Cygnus X-1
Begelman, Mitchell C.; Wilms, Joern; Dove, James B. +1 more
We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broadband X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper, models in which the Comptonizing medium is a slab surrounding the cold accretion disk cannot have a temperature higher than about 140 keV for optical d…
White Dwarfs in Globular Clusters: Hubble Space Telescope Observations of M4
Bond, Howard E.; Ibata, Rodrigo A.; Stetson, Peter B. +11 more
Using WFPC2 on the Hubble Space Telescope, we have isolated a sample of 258 white dwarfs (WDs) in the Galactic globular cluster M4. Fields at three radial distances from the cluster center were observed, and sizable WD populations were found in all three. The location of these WDs in the color-magnitude diagram, their mean mass of 0.51(+/-0.03) M<…
Dust and Recent Star Formation in the Core of NGC 5253
Meurer, Gerhardt R.; Calzetti, Daniela; Leitherer, Claus +4 more
Ultraviolet and optical narrow and broad band images of NGC 5253 obtained with the Hubble Space Telescope Wide Field and Planetary Camera 2 are used to derive the properties of the dust distribution and the recent star formation history of this metal-poor dwarf galaxy. Corrections for the effects of dust are important in the center of NGC 5253: du…
Dynamics of Broad Emission-Line Region in NGC 5548: Hydromagnetic Wind Model versus Observations
Korista, Kirk T.; Blandford, Roger D.; Bottorff, Mark +1 more
We analyze the results of long-term observations of the broad-line region (BLR) in the Seyfert 1 galaxy NGC 5548 and provide a critical comparison with the predictions of a hydromagnetically driven outflow model of Emmering, Blandford, & Shlosman. We use this model to generate a time series of C IV line profiles that have responded to a time-v…
A Catalog and Atlas of Cataclysmic Variables-Second Edition
Shara, Michael M.; Downes, Ronald; Webbink, Ronald F.
We present a catalog of all 1020 known cataclysmic variables (CVs). This paper is a major update of the first edition of the catalog (Downes and Shara 1993, PASP, 105, 127), which contained coordinates (measured in the reference frame of the Hubble Space Telescope Guide Star Survey for the non-novae, and obtained from the literature for the novae)…
The First Direct Measurement of the Mass of a Blue Straggler in the Core of a Globular Cluster: BSS 19 in 47 Tucanae
Livio, Mario; Saffer, Rex A.; Shara, Michael M.
Hot, young blue straggler stars are observed by the Hubble Space Telescope to exist in the cores of very old globular clusters. Theory maintains that these stars must be more massive than hydrogen-burning cluster members that are as old as the clusters themselves. We have, for the first time, verified this theoretical claim by directly measuring t…
The Dwarf Irregular Galaxy Sextans A. II. Recent Star Formation History
Skillman, Evan D.; Saha, A.; Gallagher, J. +6 more
We have used the Hubble Space Telescope to obtain photometric data of the resolved stars in the nearby (D = 1.4 Mpc) dwarf irregular galaxy Sextans A (DDO 75, A 1008-04). The data consist of WFPC2 images in 3 bands: F439W (1 hour), F555W (30 minutes), and F814W (30 minutes). We constructed very accurate color-magnitude diagrams (CMDs) in V and I d…
Hubble Space Telescope Observations of the Blue Compact Dwarf SBS 0335-052: A Probable Young Galaxy
Thuan, Trinh X.; Izotov, Yuri I.; Lipovetsky, Valentin A.
We present HST WFPC2 V and I images and GHRS UV spectrophotometry of the spectral regions around Lyα and O I λ1302 of the extremely metal-deficient (Z ~ Z⊙/41) blue compact dwarf galaxy (BCD) SBS 0335-052. All the star formation in the BCD occurs in six super-star clusters (SSCs) with ages <=25 Myr, within a region of ~2" or 520 pc i…
Carbon in the Diffuse Interstellar Medium
Sofia, Ulysses J.; Meyer, David M.; Cardelli, Jason A. +1 more
We have obtained spectra of the interstellar intersystem C II] λ2325 line toward the star τ Canis Majoris. The absorption spectra were obtained with the echelle mode (3.5 km s-1 resolution) of the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope and have a co-added signal-to-noise ratio of approximately 850. The C …