Search Publications
Self-Consistent Dynamic Models of Steady Ionization Fronts. I. Weak-D and Weak-R Fronts
Henney, W. J.; Ferland, G. J.; Williams, R. J. R. +1 more
We present a method for including steady state gas flows in the plasma physics code Cloudy, which was previously restricted to modeling static configurations. The numerical algorithms are described in detail, together with an example application to plane-parallel ionization-bounded H II regions. As well as providing the foundation for future appli…
A Candidate Neutron Star Associated with Galactic Center Supernova Remnant Sagittarius A East
Maeda, Yoshitomo; Garmire, Gordon P.; Baganoff, Frederick K. +6 more
We present imaging and spectral studies of the supernova remnant (SNR) Sagittarius (Sgr) A East from deep observations with Chandra. The spatially resolved spectral analysis of Sgr A East reveals the presence of a two-temperature thermal plasma (kT~1 and 5 keV) near the center of the SNR. The central region is dominated by emission from highly ion…
Absolute Proper Motion of the Sagittarius Dwarf Galaxy and of the Outer Regions of the Milky Way Bulge
Girard, Terrence M.; van Altena, William F.; López, Carlos E. +1 more
We have determined the absolute proper motion of the Sagittarius dwarf spheroidal galaxy (Sgr) from the Southern Proper Motion Catalog 3, by selecting red giant candidates from the Two Micron All Sky Survey. We obtain µlcosb=-2.35+/-0.20 and µb=2.07+/-0.20 mas yr-1. Using the same procedure, we also det…
Catastrophic Cooling of Impulsively Heated Coronal Loops
Erdélyi, Robert; Mendoza-Briceño, César A.; Sigalotti, Leonardo Di G.
The physical mechanisms that cause the heating of the solar corona are still far from being completely understood. However, recent highly resolved observations with the current solar missions have shown clear evidence of frequent and very localized heating events near the chromosphere that may be responsible for the observable high temperatures of…
Radio and X-Ray Signatures of Magnetic Reconnection behind an Ejected Flux Rope
Pick, M.; Krucker, S.; Démoulin, P. +2 more
We present a detailed study of a complex solar event observed on 2002 June 2. Joint imaging EUV, X-ray, and multiwavelength radio observations allow us to trace the development of the magnetic structure involved in this solar event up to a radial distance of the order of 2 Rsolar. The event involves type II, III, and IV bursts. The type…
Limits from the Hubble Space Telescope on a Point Source in SN 1987A
Filippenko, Alexei V.; Garnavich, Peter; Fransson, Claes +16 more
We observed supernova 1987A (SN 1987A) with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) in 1999 September and again with the Advanced Camera for Surveys (ACS) on the HST in 2003 November. Our spectral observations cover ultraviolet (UV) and optical wavelengths from 1140 to 10266 Å, and our imaging observatio…
Three-dimensional Structure of Coronal Mass Ejections from LASCO Polarization Measurements
Wang, Dennis; Dere, Kenneth P.; Howard, Russell
The three-dimensional structure of a coronal mass ejection (CME) is essential information for understanding the process by which they are ejected from the Sun. Coronagraphic measurements readily provide information on the structure of CMEs in the plane of the sky. It has been known for some time that polarization measurements can provide informati…
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
Peterson, Bradley M.; Vestergaard, Marianne
We study the low-contrast Fe II emission blends in the ultraviolet (1250-2200 Å) and optical (4000-6000 Å) spectra of the Seyfert 1 galaxy NGC 5548 and show that these features vary in flux and that these variations are correlated with those of the optical continuum. The amplitude of variability of the optical Fe II emission is 50%-75% that of Hβ,…
Reevaluation of the Magnetic Structure and Evolution Associated with the Bastille Day Flare on 2000 July 14
Zhang, Hongqi; Liu, Chang; Wang, Haimin +1 more
The Bastille Day flare on 2000 July 14 was well observed by several space- and ground-based observatories and studied extensively by many researchers. Recently, we discovered that a large fraction of X-class flares are associated with a very interesting evolutionary pattern in δ sunspots: part of the outer δ spot structure decays rapidly after maj…
XMM-Newton Observation of an X-Ray Trail between the Spiral Galaxy NGC 6872 and the Central Elliptical Galaxy NGC 6876 in the Pavo Group
Jones, Christine; Forman, William R.; Nulsen, Paul +2 more
We present XMM-Newton observations of a trail of enhanced X-ray emission extending along the full 8.7 arcmin ×4' region between the large spiral galaxy NGC 6872 and the dominant elliptical galaxy NGC 6876 in the Pavo group, the first known X-ray trail associated with a spiral galaxy in a poor galaxy group and, with a projected length of…