Search Publications
The Ultraviolet Extinction Curve of Intraclump Dust in Taurus (TMC-1): Constraints on the 2175 Å Bump Absorber
Gordon, Karl D.; Whittet, D. C. B.; Clayton, Geoffrey C. +1 more
Ultraviolet extinction curves for three early-type stars that sample dust in the Taurus dark cloud in the vicinity of TMC-1 are analyzed to examine the contribution of internal (intraclump) dust to the total line-of-sight extinction. One of our selected targets samples only dust in the ``diffuse-screen'' component of the cloud, where the dust grai…
Helioseismic Mapping of the Magnetic Canopy in the Solar Chromosphere
Finsterle, W.; McIntosh, S. W.; Jefferies, S. M. +2 more
We determine the three-dimensional topography of the magnetic canopy in and around active regions by mapping the propagation behavior of high-frequency acoustic waves in the solar chromosphere.
Revealing the X-Ray Emission Processes of Old Rotation-powered Pulsars: XMM-Newton Observations of PSR B0950+08, PSR B0823+26, and PSR J2043+2740
Weisskopf, Martin C.; Tennant, Allyn F.; Becker, Werner +4 more
We have completed part of a program to study the X-ray emission properties of old rotation-powered pulsars with XMM-Newton in order to probe and identify the origin of their X-radiation. The X-ray emission from these old pulsars is largely dominated by nonthermal processes. None of the observed spectra required adding a thermal component consistin…
A Multiwavelength Scattered Light Analysis of the Dust Grain Population in the GG Tauri Circumbinary Ring
Duchêne, G.; Ghez, A. M.; Macintosh, B. A. +1 more
We present the first 3.8 µm image of the dusty ring surrounding the young binary system GG Tau, obtained with the W. M. Keck II 10 m telescope's adaptive optics system. This is the longest wavelength at which the ring has been detected in scattered light so far, allowing a multiwavelength analysis of the scattering properties of the dust gra…
Radio Observation of Electron Acceleration at Solar Flare Reconnection Outflow Termination Shocks
Mann, Gottfried; Aurass, Henry
Using meter-wave solar radio spectral observations of the 2001 September 28 flare, we discuss simultaneously appearing type II-like bursts observed at 40-80 MHz and ~300 MHz as radio signatures of the upper and lower reconnection outflow termination shock (TS). The features are identified during the impulsive phase but well after the regular trave…
The Space Density of High-redshift QSOs in the Great Observatories Origins Deep Survey
Stern, D.; Alexander, D. M.; Treister, E. +14 more
We present a sample of 17 high-redshift (3.5<~z<~5.2) quasi-stellar object (QSO) candidates in the 320 arcmin2 area of the Great Observatories Origins Deep Survey, selected in the magnitude range 22.45<z850<25.25 using deep imaging with the Advanced Camera for Surveys on board the Hubble Space Telescope and the Ad…
A Transition to a Low/Soft State in the Ultraluminous Compact X-Ray Source Holmberg II X-1
Dewangan, Gulab C.; Griffiths, Richard E.; Miyaji, Takamitsu +1 more
We present three XMM-Newton observations of the ultraluminous compact X-ray source Holmberg II X-1 in its historical brightest and faintest states. The source was in its brightest state in 2002 April with an isotropic X-ray luminosity of ~2×1040 ergs s-1 but changed to a peculiar low/soft state in 2002 September in which the …
The Birth of a Super-Star Cluster: NGC 5253
Turner, Jean L.; Beck, Sara C.
We present images of the 7 mm free-free emission from the radio ``supernebula'' in NGC 5253 made with the Very Large Array and the Pie Town link. The images reveal structure in the nebula, which has a <=1 pc (~50 mas radius) core requiring the excitation of 1200 O7 stars. The nebula is elongated, with an arc of emission curving to the northeast…
Detection of He II λ4686 in η Carinae
Steiner, J. E.; Damineli, A.
We report the detection of the emission line He II λ4686 in η Carinae. The equivalent width of this line is ~100 mÅ along most of the 5.5 yr cycle and jumps to ~900 mÅ just before phase 1.0, followed by a brief disappearance. The similarity between the intensity variations of this line and those of the X-ray light curve is remarkable, suggesting t…
A Supernova Factory in the Merger System Arp 299
Teng, Stacy H.; Neff, Susan G.; Ulvestad, James S.
We have imaged the nearby galaxy merger Arp 299 at arcsecond and milliarcsecond resolution, using both the Very Large Array (VLA) and the Very Long Baseline Array. The large-scale radio emission from the merger contains five bright, compact radio sources embedded in diffuse emission, with diameters less than 200 pc. Supernova rates of 0.1-1 yr