Search Publications
Galaxy Disruption in a Halo of Dark Matter
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +2 more
The relics of disrupted satellite galaxies have been found around the Milky Way and Andromeda, but direct evidence of a satellite galaxy in the early stages of disruption has remained elusive. We have discovered a dwarf satellite galaxy in the process of being torn apart by gravitational tidal forces as it merges with a larger galaxy's dark matter…
Doubly Ionized Carbon Observed in the Plasma Tail of Comet Kudo-Fujikawa
Feldman, Paul D.; Raymond, John C.; Povich, Matthew S. +6 more
Comet C/2002 X5 (Kudo-Fujikawa) was observed near its perihelion of 0.19 astronomical unit by the Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory spacecraft. Images of the comet reconstructed from high-resolution spectra reveal a quasi-spherical cloud of neutral hydrogen and a variable tail of C+ and C…
Helioseismic Measurement of Solar Torsional Oscillations
Thompson, M. J.; Christensen-Dalsgaard, J.; Schou, J. +2 more
Bands of slower and faster rotation, the so-called torsional oscillations, are observed at the Sun's surface to migrate in latitude over the 11-year solar cycle. Here, we report on the temporal variations of the Sun's internal rotation from solar p-mode frequencies obtained over nearly 6 years by the Michelson Doppler Imager (MDI) instrument on bo…
A Classical Nova, V2487 Oph 1998, Seen in X-rays Before and After Its Explosion
Hernanz, Margarita; Sala, Glòria
Classical nova explosions are very energetic and frequent phenomena caused by explosive hydrogen burning on top of an accreting white dwarf. Observations of the recent nova V2487 Oph 1998 by the X-ray Multi-Mirror satellite (XMM-Newton) provide evidence that accretion (probably on a magnetic white dwarf) was reestablished as early as 2.7 years aft…
Formation of the Three-Ring Structure Around Supernova 1987A
Tanaka, T.; Washimi, H.
From a magnetohydrodynamic simulation, we reproduce a three-ring structure in the circumstellar space of the supernova (SN) 1987A observed by the Hubble Space Telescope. When a star develops from a red supergiant (RSG) to a blue supergiant (BSG) just before the SN explosion, a wind-wind interaction occurs between the slow stellar wind from the RSG…
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…