Search Publications
Isolated OB Associations in Stripped H I Gas Clouds
Freeman, K. C.; Ryan-Weber, E. V.; Oey, M. S. +4 more
HST ACS HRC images in UV (F250W), V (F555W), and I (F814W) resolve three isolated OB associations that lie up to 30 kpc from the stellar disk of the S0 galaxy NGC 1533. Previous narrowband Hα imaging and optical spectroscopy showed these objects as unresolved intergalactic H II regions having Hα luminosities consistent with single early-type O sta…
Observations of Doppler Shift Oscillations with the EUV Imaging Spectrometer on Hinode
Warren, Harry P.; Watanabe, Tetsuya; Mariska, John T. +1 more
Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory and with the Bragg Crystal Spectrometer on Yohkoh. This Letter reports the detection of low-amplitude damped oscillations i…
Damping of Slow MHD Coronal Loop Oscillations by Shocks
Verwichte, E.; Haynes, M.; Arber, T. D. +1 more
The damping of slow magnetoacoustic coronal loop oscillations by shock dissipation is investigated. Observations of large-amplitude slow-mode observations made by SUMER show a clear dependency of the damping rate on the oscillation amplitude. Fully nonlinear MHD simulations of slow-mode oscillations in the presence of thermal conduction are perfor…
GALEX Spectroscopy of SN 2005ay Suggests Ultraviolet Spectral Uniformity among Type II-P Supernovae
Smith, G. P.; Gal-Yam, A.; Kirshner, R. P. +24 more
We present the initial results from our GALEX program designed to obtain ultraviolet (UV) spectra of nearby core-collapse supernovae (SNe). Our first target, SN 2005ay in the nearby galaxy NGC 3938, is a typical member of the SN II-P subclass. Our spectra show remarkable similarity to those of the prototypical Type II-P SN 1999em, and resemble als…
Analysis of Interplanetary Coronal Mass Ejection Parameters as a Function of Energetics, Source Location, and Magnetic Structure
Reinard, A. A.
We describe a study of how ICME parameters vary as function of source location, associated flare magnitude, and magnetic structure. The strongest compositional enhancements are found to occur in events originating in central longitudes of the Sun, those with large associated flares, and those that are identified as magnetic clouds. In situ velocit…
Millisecond Microwave Spikes: Statistical Study and Application for Plasma Diagnostics
Rozhansky, I. V.; Fleishman, G. D.; Huang, G. -L.
We analyze a dense cluster of solar radio spikes registered at 4.5-6 GHz by the Purple Mountain Observatory spectrometer (Nanjing, China), operating in the 4.5-7.5 GHz range with 5 ms temporal resolution. To handle the data from the spectrometer, we developed a new technique that uses a nonlinear multi-Gaussian spectral fit based on χ2 …
The Effect of Magnetic Reconnection and Writhing in a Partial Filament Eruption
Liu, Rui; Alexander, David; Gilbert, Holly R. +1 more
We present observations from 2007 March 2 of a partial filament eruption characterized by two distinct phases of writhing motions: a quasi-static, slowly evolving phase followed by a rapid kinking phase showing a bifurcation of the filament. The quasi-static kinking motions are observed before there is any heating or flaring evident in EUV or soft…
The Shape of Cas A
Wheeler, J. Craig; Maund, Justyn R.; Couch, Sean M.
On the basis of optical, IR, and X-ray studies of Cas A, we propose a geometry for the remnant based on a "jet-induced" scenario with significant systematic departures from axial symmetry. In this model, the main jet axis is oriented in the direction of strong blueshifted motion at an angle of 110°-120° east of north and about 40°-50° to the east …
Spatial Distribution of Magnetic Reconnection in the 2006 December 13 Solar Flare as Observed by Hinode
Jing, Ju; Wang, Haimin; Chae, Jongchul
A massive two-ribbon flare and its source magnetic field region were well captured by the Solar Optical Telescope (SOT) on board Hinode in the Ca II H spectral line and by the Spectro-Polarimeter of SOT, respectively. Using the high-resolution Hinode data sets, we compare the spatial distribution of the local magnetic reconnection rate and the ene…
An Ultraluminous Supersoft X-Ray Source in M81: An Intermediate-Mass Black Hole?
Liu, Jifeng; Di Stefano, Rosanne
Ultraluminous supersoft X-ray sources (ULSSSs) exhibit supersoft spectra with blackbody temperatures of 50-100 eV and bolometric luminosities above 1039 ergs s-1 and are possibly intermediate-mass black holes (IMBHs) of >=103 M⊙ or massive white dwarfs that are progenitors of Type Ia supernovae. In th…