Search Publications
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…
The host galaxy/AGN connection. Brightness profiles of early-type galaxies hosting Seyfert nuclei
Capetti, A.; Balmaverde, B.
We recently presented evidence of a connection between the brightness profiles of nearby early-type galaxies and the properties of the AGN they host. The radio loudness of the AGN appears to be univocally related to the host's brightness profile: radio-loud nuclei are only hosted by “core” galaxies while radio-quiet AGN are only found in “power-la…
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 …
Absorption and reflection of radio waves in the Martian ionosphere
Morgan, D. D.; Picardi, G.; Kirchner, D. L. +2 more
Radio wave absorption in the Martian ionosphere has been predicted and tested against MARSIS radar observations. Models of the ionosphere densities and of absorption in a CO2 neutral atmosphere were used. The appearance of ground reflections in the MARSIS observations is shown to be consistent with predictions of reflection and absorpti…
Evolution of ring current and radiation belt particles under the influence of storm-time electric fields
Nishimura, Y.; Shinbori, A.; Ono, T. +2 more
Electric field and potential distributions in the inner magnetosphere during geomagnetic storms have been investigated using the Akebono/EFD data. Using this electric field, we study injection of ring current particles and acceleration of radiation belt electrons by single-particle calculations. During the main phase, the dawn-dusk electric field …
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 …
Observations of Transient Active Region Heating with Hinode
Warren, Harry P.; Hara, Hirohisa; Ugarte-Urra, Ignacio +3 more
We present observations of transient active region heating events observed with the Extreme Ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope (XRT) on Hinode. This initial investigation focuses on NOAA active region 10940 as observed by Hinode on 2007 February 1 between 12 and 19UT. In these observations we find numerous examples of trans…
Are solar maximum fan streamers a consequence of twisting sheet structures?
Habbal, S. R.; Morgan, H.
Context: Fan streamers are often observed at low to mid latitudes in the corona at solar maximum, appearing narrow in latitudinal extent near the Sun, and fanning out with height, adopting an approximately linear, but not necessarily radial, configuration above ~3 R⊙.
Aims: We offer arguments to support the conjecture that such stru…
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…