Search Publications
High-Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
Heinke, Craig; Murray, Stephen S.; Edmonds, Peter D. +1 more
We have obtained high-resolution (<~1'') deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (Lx ~ 1030-33 e…
Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer
Kruk, J. W.; Shull, J. M.; Sembach, K. R. +16 more
The neutral hydrogen (H I) and ionized helium (He II) absorption in the spectra of quasars are unique probes of structure in the early universe. We present Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the quasar HE2347-4342 in the 1000 to 1187 angstrom band at a resolving power of 15,000. We resolve the He II Lyman α…
No Supermassive Black Hole in M33?
Joseph, Charles L.; Ferrarese, Laura; Merritt, David
We observed the nucleus of M33, the third-brightest galaxy in the Local Group, with the Space Telescope Imaging Spectrograph at a resolution at least a factor of 10 higher than previously obtained. Rather than the steep rise expected within the radius of gravitational influence of a supermassive black hole, the random stellar velocities showed a d…
HST and VLT Investigations of the Fragments of Comet C/1999 S4 (LINEAR)
Jorda, L.; Lamy, P. L.; Feldman, P. D. +18 more
At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass i…
Outgassing Behavior and Composition of Comet C/1999 S4 (LINEAR) During Its Disruption
Weaver, H. A.; Lis, Dariusz C.; Bockelée-Morvan, Dominique +9 more
The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (<=30-centimeter radius) was comparable to the mass in the large fragments seen in optical images. The mass bud…
Evidence for Dust Grain Growth in Young Circumstellar Disks
Throop, Henry B.; Bally, John; Esposito, Larry W. +1 more
Hundreds of circumstellar disks in the Orion nebula are being rapidly destroyed by the intense ultraviolet radiation produced by nearby bright stars. These young, million-year-old disks may not survive long enough to form planetary systems. Nevertheless, the first stage of planet formation-the growth of dust grains into larger particles-may have b…
Imaging and Photometry of Comet C/1999 S4 (LINEAR) Before Perihelion and After Breakup
Woodney, Laura M.; Schleicher, David G.; Farnham, Tony L. +3 more
We analyzed photometric measurements and images of comet C/LINEAR before perihelion and after its breakup. Results from our photometry data include a lower limit of 0.44 kilometer for the radius of the nucleus before breakup, and a determination that it was depleted in carbon-chain molecules relative to most other comets. Our imaging and modeling …