Search Publications
Computational Acoustics in Spherical Geometry: Steps toward Validating Helioseismology
Christensen-Dalsgaard, J.; Schou, J.; Roth, M. +6 more
Throughout the past decade, detailed helioseismic analyses of observations of solar surface oscillations have led to advances in our knowledge of the structure and dynamics of the solar interior. Such analyses involve the decomposition of time series of the observed surface oscillation pattern into its constituent wave modes, followed by inversion…
Three-dimensional Simulation of Gamma-Ray Emission from Asymmetric Supernovae and Hypernovae
Maeda, Keiichi
Hard X- and γ-ray spectra and light curves resulting from radioactive decays are computed for aspherical (jetlike) and energetic supernova models (representing the prototypical hypernova SN 1998bw), using a three-dimensional energy- and time-dependent Monte Carlo scheme. The emission is characterized by (1) early emergence of high-energy emission,…
A Stellar-Mass Black Hole in the Ultraluminous X-Ray Source M82 X-1?
Okajima, Takashi; Ebisawa, Ken; Kawaguchi, Toshihiro
We have analyzed the archival XMM-Newton data of the bright ultraluminous X-ray source M82 X-1 with a 105 ks exposure when the source was in the steady state. Thanks to the high photon statistics from the large effective area and long exposure, we were able to discriminate different X-ray continuum spectral models. Neither the standard accretion d…
Role of the Sun's Nonaxisymmetric Open Flux in Cosmic-Ray Modulation
Rouillard, A. P.; Sheeley, N. R., Jr.; Wang, Y. -M.
We reexamine the empirical relationship between the Sun's open magnetic flux and the cosmic-ray (CR) intensity over the solar cycle. The single parameter that correlates best with the inverted CR rate is found to be the nonaxisymmetric or longitudinally varying component of the total open flux, rather than the sunspot number or the rate of coronal…
Optical Polarimetry of the Jets of Nearby Radio Galaxies. I. The Data
Baum, Stefi A.; O'Dea, Christopher P.; Perlman, Eric S. +11 more
We present an overview of new HST imaging polarimetry of six nearby radio galaxies with optical jets. These observations triple the number of extragalactic jets with subarcsecond-resolution optical polarimetry. We discuss the polarization characteristics and optical morphology of each jet. We find evidence of high optical polarization, averaging 2…
A Comprehensive Search for Gamma-Ray Lines in the First Year of Data from the INTEGRAL Spectrometer
Teegarden, B. J.; Watanabe, K.
We have carried out an extensive search for gamma-ray lines in the first year of public data from the spectrometer (SPI) on the INTEGRAL mission. INTEGRAL has spent a large fraction of its observing time in the Galactic plane with particular concentration in the Galactic center (GC) region (~3 Ms in the first year). Hence the most sensitive search…
Flares, Magnetic Fields, and Subsurface Vorticity: A Survey of GONG and MDI Data
Howe, R.; Komm, R.; Hill, F. +3 more
We search for a relation between flows below active regions and flare events occurring in those active regions. For this purpose, we determine the subsurface flows from high-resolution Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) Dynamics Program data using the ring-diagram technique. We then calculate the vorticity o…
The Chandra, Hubble Space Telescope, and VLA View of the Circumnuclear Extended Emission in the Narrow Emission Line Galaxy NGC 2110
Gallagher, Sarah C.; Lee, Julia C.; Kraft, Ralph P. +4 more
We present results from new Chandra, archival Hubble Space Telescope (HST), and VLA imaging observations of the circumnuclear extended emission in the nearby Type 2 Seyfert galaxy NGC 2110. We find resolved soft-band X-ray emission ~4" (~160 pc) north of the nucleus, which is spatially coincident with [O III] emission, but lies just beyond the nor…
Multiwavelength Observations of EXO 0748-676. II. Emission-Line Behavior
O'Brien, K.; King, A. R.; Nelemans, G. +6 more
We present optical and ultraviolet spectra, light curves, and Doppler tomograms of the low-mass X-ray binary EXO 0748-676. Using an extensive set of 15 emission-line tomograms, we show that, along with the usual emission from the stream and ``hot spot,'' there is extended nonaxisymmetric emission from the disk rim. Some of the emission and Hα and …
Lensing Magnification of Supernovae in the GOODS Fields
Goobar, A.; Mörtsell, E.; Lee, K. +3 more
Gravitational lensing of high-redshift supernovae is potentially an important source of uncertainty when cosmological parameters are being derived from the measured brightness of Type Ia supernovae, especially in deep surveys with scarce statistics. Photometric and spectroscopic measurements of foreground galaxies along the lines of sight of 33 su…