Search Publications
Abundances in the H I Envelope of the Extremely Low Metallicity Blue Compact Dwarf Galaxy SBS 0335-052 from Far Ultraviolet Spectroscopic Explorer Observations
Thuan, Trinh X.; Izotov, Yuri I.; Lecavelier des Etangs, Alain
We present Far Ultraviolet Spectroscopic Explorer spectroscopy of SBS 0335-052, the second most metal-deficient blue compact dwarf (BCD) galaxy known [log(O/H)=-4.70]. In addition to the H I Lyman series, we detect C II, N I, N II, O I, Si II, Ar I, and Fe II absorption lines, mainly arising from the extended H I envelope in which SBS 0335-052 is …
Discovery of Extremely Embedded X-Ray Sources in the R Coronae Australis Star-forming Core
Hamaguchi, Kenji; Corcoran, Michael F.; Petre, Rob +5 more
With the XMM-Newton and Chandra observatories, we detected two extremely embedded X-ray sources in the R Corona Australis (R CrA) star-forming core, near IRS 7. These sources, designated as XE and XW, have X-ray absorption columns of ~3×1023 cm-2 equivalent to AV~180 mag. They are associated w…
Distribution of the Magnetic Flux in Elements of the Magnetic Field in Active Regions
Abramenko, V. I.; Longcope, D. W.
The unsigned magnetic flux content in the flux concentrations of two active regions is calculated by using a set of 248 high-resolution Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms for each active region. Data for flaring active region NOAA 9077 (2000 July 14) and nonflaring active region NOAA 0061 (2002 August 9) were …
Diamagnetic and Expansion Effects on the Observable Properties of the Slow Solar Wind in a Coronal Streamer
Velli, M.; Dahlburg, R. B.; Einaudi, G. +1 more
The plasma density enhancements recently observed by the Large-Angle Spectrometric Coronagraph (LASCO) instrument on board the Solar and Heliospheric Observatory (SOHO) spacecraft have sparked considerable interest. In our previous theoretical study of the formation and initial motion of these density enhancements it is found that beyond the helme…
A Mode-Fitting Methodology Optimized for Very Long Helioseismic Time Series
Korzennik, S. G.
I describe and present the results of a newly developed fitting methodology optimized for very long time series. The development of this new methodology was motivated by the fact that we now have more than half a decade of nearly uninterrupted observations by the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), with …
Evidence of a Starburst within 9 Parsecs of the Active Nucleus of NGC 1097
Filippenko, A. V.; Storchi-Bergmann, T.; Wilson, A. S. +4 more
We report evidence of a recent burst of star formation located within 9 pc of the active nucleus of NGC 1097. The observational signatures of the starburst include UV absorption lines and continuum emission from young stars observed in a small-aperture Hubble Space Telescope spectrum. The burst is <= a few × 106 yr old, has a mass of…
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…