Search Publications
Small Polycyclic Aromatic Hydrocarbons in the Red Rectangle
Gordon, Karl D.; Witt, Adolf N.; Vijh, Uma P.
Following our initial discovery of blue luminescence in the spectrum of the Red Rectangle (RR) and its identification as fluorescence by small three- to four-ringed polycyclic aromatic hydrocarbon (PAH) molecules, we report on the spatial correlation between the blue luminescence and the 3.3 µm emission, commonly attributed to small, neutral…
A Comparison of Absorption- and Emission-Line Abundances in the Nearby Damped Lyα Galaxy SBS 1543+593
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +1 more
We have used STIS aboard HST to measure a sulfur abundance of [S/H]=-0.41+/-0.06 in the ISM of the nearby DLA galaxy SBS 1543+593. A direct comparison between this QSO absorption line abundance and abundances measured from H II region emission line diagnostics yields the same result: the abundance of sulfur in the neutral ISM is in good agreement …
The Effect of Stellar Evolution on SiC Dust Grain Sizes
Speck, Angela K.; Thompson, Grant D.; Hofmeister, Anne M.
Stars on the asymptotic giant branch (AGB) produce dust in their circumstellar shells. The nature of the dust-forming environment is influenced by the evolution of the stars, in terms of both chemistry and density, leading to an evolution in the nature of the dust that is produced. Carbon-rich AGB stars are known to produce silicon carbide (SiC). …
A Comparative Study of the Spatial Distribution of Ultraviolet and Far-Infrared Fluxes from M101
Heckman, Timothy M.; Madore, Barry F.; Tuffs, Richard J. +23 more
The total ultraviolet (UV) flux (from 1412 to 2718 Å) of M101 is compared on a pixel-to-pixel basis with the total far-infrared (FIR) flux (from 60 to 170 µm) using the maps of the galaxy taken by the Galaxy Evolution Explorer (GALEX) in the near-UV and far-UV and by the Infrared Space Observatory (ISO) at 60, 100, and 170 µm. The main…
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…