Search Publications
Is There a High-Energy Particle Population in the Quiet Solar Corona?
Doschek, G. A.; Feldman, U.; Ralchenko, Yu.
A study of spectra emitted by the quiet solar corona indicates that the majority of line intensities originating in low-lying levels are consistent with isothermal plasma of ~1.3×106 K. Nevertheless, a number of line intensities and, in particular, those belonging to ions that are typical of higher temperatures are brighter than expecte…
Search for Electron-Positron Annihilation Radiation from the Jet in 3C 120
McHardy, Ian M.; Agudo, Iván; Jorstad, Svetlana G. +3 more
We report an attempt to detect the electron-positron annihilation line from the radio galaxy 3C 120, in which the jet interacts strongly with interstellar clouds. Such interactions should cause most of the jet plasma to mix with the gas in the clouds. This will thermalize the majority of any positrons in the jet, leading to continuous annihilation…
Near- to Mid-Infrared Spectroscopy for the Giant Elliptical Galaxy NGC 1316 (Fornax A) with the AKARI Infrared Camera
Onaka, T.; Sakon, I.; Kaneda, H.
We present the near- to mid-infrared (~2.5-13 µm) spectrum of the giant elliptical galaxy NGC 1316 (Fornax A) obtained with the Infrared Camera (IRC) on board AKARI. NGC 1316 is known to have a peculiar polycyclic aromatic hydrocarbon (PAH) emission spectrum with an unusually high ratio of the 11.3 µm to the 7.7 µm emission inten…
RHESSI and Hinode X-Ray Observations of a Partially Occulted Solar Flare
Krucker, Säm; Lin, R. P.; Hannah, I. G.
This Letter presents X-ray observations of a partially limb-occulted solar flare taken by the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the X-ray telescope on board Hinode. Thermal emission originates from a simple loop at the western limb that rises slowly (~7 km s-1) until the flare peak time. Above 18 keV, faint nonthe…
What Determines the Intensity of Solar Flare/CME Events?
Reeves, Katharine K.; Golub, Leon; Su, Yingna +3 more
We present a comprehensive statistical study addressing the question of what determines the intensity of a solar flare and associated coronal mass ejection (CME). For a sample of 18 two-ribbon flares associated with CMEs, we have examined the correlations between the GOES soft X-ray peak flare flux (PFF), the CME speed (VCME) obtained f…
Are High-Redshift Quasars Blurry?
Steinbring, Eric
It has been suggested that the fuzzy nature of spacetime at the Planck scale may cause light waves to lose phase coherence, and if severe enough this could blur images of distant pointlike sources sufficiently that they do not form an Airy pattern at the focal plane of a telescope. Blurring this dramatic has already been observationally ruled out …
The Sextet Arcs: A Strongly Lensed Lyman Break Galaxy in the ACS Spectroscopic Galaxy Survey toward Abell 1689
Broadhurst, Tom; Frye, Brenda L.; Bowen, David V. +11 more
We present results of the HST Advanced Camera for Surveys spectroscopic ground-based redshift survey in the field of A1689. We measure 98 redshifts, increasing the number of spectroscopically confirmed objects sixfold. We present two spectra from this catalog of the Sextet Arcs, images that arise from a strongly lensed Lyman break galaxy (LBG) at …
Energy Distribution of Individual Quasars from Far-Ultraviolet to X-Rays. I. Intrinsic Ultraviolet Hardness and Dust Opacities
Nicastro, Fabrizio; Krongold, Yair; Humphrey, Andrew +4 more
Using Chandra and HST archival data, we have studied the individual SED of 11 quasars at redshifts 0.3<z<1.8. All UV spectra show a spectral break around 1100 Å. Five X-ray spectra showed the presence of a ``soft excess,'' and seven spectra showed an intrinsic absorption. We found that for most quasars a simple extrapolation of the far-UV po…
Magnetic Cycles in the Sun: Modeling the Changes in Radius, Luminosity, and p-Mode Frequencies
Mullan, D. J.; Townsend, R. H. D.; MacDonald, J.
We report on the results obtained with a stellar evolution code in which cyclic magnetic fields are imposed in the convection zone of a 1.0 Msolar star. Magnetic effects are incorporated in two ways: (1) the field pressure and energy density are included in the equations of hydrostatic equilibrium and conservation of energy; and (2) the…
Spatially Resolved X-Ray Spectra of NGC 4258
Yang, Y.; Li, B.; Reynolds, C. S. +1 more
We report a spatially resolved, X-ray spectral analysis of NGC 4258 using archival Chandra and XMM-Newton observations. The XMM-Newton spectrum of the nuclear region is well described by two power-law components, a soft (0.57 keV) thermal component and an Fe Kα line with EW=40+/-33 eV. The properties of the second, weaker power-law component are s…