Search Publications
Hydrostatic Modeling of the Integrated Soft X-Ray and Extreme Ultraviolet Emission in Solar Active Regions
Winebarger, Amy R.; Warren, Harry P.
Many studies of the solar corona have shown that the observed X-ray luminosity is well correlated with the total unsigned magnetic flux. In this paper we present results from the extensive numerical modeling of active regions observed with the Solar and Heliospheric Observatory (SOHO) EUV Imaging Telescope (EIT), the Yohkoh Soft X-Ray Telescope (S…
High-Resolution Observations of Multiwavelength Emissions during Two X-Class White-Light Flares
Xu, Yan; Cao, Wenda; Liu, Chang +5 more
We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the …
Accretion and Nuclear Activity of Quiescent Supermassive Black Holes. I. X-Ray Study
Elvis, M.; Graham, Alister W.; Pellegrini, S. +5 more
We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~1038-1039 ergs s-1 (LX/LEdd~10-8 to 10-7) and colors or spectra consistent with acc…
On the He II Emission in η Carinae and the Origin of Its Spectroscopic Events
Davidson, K.; Hillier, D. J.; Humphreys, Roberta M. +2 more
We describe and analyze Hubble Space Telescope (HST) observations of transient emission near 4680 Å in η Car, reported earlier by Steiner & Damineli. If, as seems probable, this is He II λ4687, then it is a unique clue to η Car's 5.5 yr cycle. According to our analysis, several aspects of this feature support a mass-ejection model of the obser…
Trends in the Globular Cluster Luminosity Function of Early-Type Galaxies
Jordán, Andrés; Tonry, John L.; Côté, Patrick +8 more
We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 early-type galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parameterization of the GCLF, we find a highly significant correlation between the GCLF dispersion, σ, and the galaxy luminosity, MB,gal, in the sense…
Spitzer IRAC Images and Sample Spectra of Cassiopeia A's Explosion
Smith, J. D.; Reach, William T.; Rho, Jeonghee +5 more
We present Spitzer IRAC images and representative 5.27-38.5 µm IRS spectra of the Cas A SNR. We find that various IRAC channels are each most sensitive to a different spectral and physical component. Channel 1 (3.6 µm) provides an excellent match to the radio synchrotron images. Where channel 1 is strong with respect to the other IRAC …
Stochastic Acceleration in the Galactic Center HESS Source
Melia, Fulvio; Liu, Siming; Petrosian, Vahé +1 more
Stochastic acceleration of electrons interacting resonantly with a turbulent magnetic field in a small accretion torus appears to be the likely mechanism responsible for much of Sagittarius A*'s millimeter and shorter wavelength spectrum. The longer wavelength radiation is produced at larger radii by electrons either diffusing from smaller scales …
Central Star Formation and PAH Profiles in Pseudobulges and Classical Bulges
Fisher, David B.
I use Spitzer 3.6-8.0 µm color profiles and surface brightness profiles of polycyclic aromatic hydrocarbons (PAHs) to compare the radial structure of star formation in pseudobulges and classical bulges. Pseudobulges are ``bulges'' that form through secular evolution, rather than mergers. In this study, pseudobulges are identified using the p…
A Near-Infrared Analysis of the Submillimeter Background and the Cosmic Star-Formation History
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
We use new deep NIR and MIR observations to analyze the 850 µm image of the GOODS-N region. We show that much of the submillimeter background is picked out by sources with H(AB) or 3.6 µm(AB)<23.25 (1.8 µJy). These sources contribute an 850 µm background of 24+/-2 Jy deg-2. This is a much higher fraction of th…
XMM-Newton Observations of the Supernova Remnant IC 443. I. Soft X-Ray Emission from Shocked Interstellar Medium
Troja, E.; Bocchino, F.; Reale, F.
The shocked interstellar medium around IC 443 produces strong X-ray emission in the soft energy band (E<~1.5 keV). We present an analysis of such emission as observed with the EPIC MOS cameras on board the XMM-Newton observatory, with the purpose to find clear signatures of the interactions with the interstellar medium (ISM) in the X-ray band, …