Search Publications
Anomalous Ultraviolet Line Flux Ratios in the Cataclysmic Variables 1RXS J232953.9+062814, CE 315, BZ Ursae Majoris, and EY Cygni, Observed with the Hubble Space Telescope Space Telescope Imaging Spectrograph
Szkody, Paula; Sion, Edward M.; Hubeny, Ivan +6 more
Brief Hubble Space Telescope Space Telescope Imaging Spectrograph spectroscopic snapshot exposures of the cataclysmic variables 1RXS J232953.9+062814, CE 315, BZ UMa, and EY Cyg reveal very large N V/C IV line flux ratios, similar to those observed in AE Aqr. Such anomalous line flux ratios have so far been observed in 10 systems and presumably re…
Molecular Gas in NUclei of GAlaxies (NUGA). I. The counter-rotating LINER NGC 4826
Tacconi, L. J.; Hunt, L. K.; Schinnerer, E. +8 more
We present new high-resolution observations of the nucleus of the counter-rotating LINER NGC 4826, made in the J=1-0 and J=2-1 lines of 12CO with the IRAM Plateau de Bure mm-interferometer(PdBI).The CO maps, which achieve 0.8arcsec (16 pc) resolution in the 2-1 line, fully resolve an inner molecular gas disk which is truncated at an out…
Observations of 1000 km s−1 Doppler shifts in 107 K solar flare supra-arcade
Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang
An X1.5 flare on the west limb of the Sun on 21 April 2002 developed a large supra-arcade about 30 min after flare onset. The growth of the supra-arcade can be followed in both TRACE 195 Å images and SUMER spectra. Its growth seems to be associated with dark (in TRACE images), sunward moving channels that descend onto the arcade from above. SUMER …
The DEEP Groth Strip Survey. VII. The Metallicity of Field Galaxies at 0.26 < z < 0.82 and the Evolution of the Luminosity-Metallicity Relation
Kobulnicky, Henry A.; Weiner, Benjamin J.; Faber, S. M. +6 more
Using spectroscopic data from the Deep Extragalactic Evolutionary Probe Groth Strip Survey (DGSS), we analyze the gas-phase oxygen abundances in the warm ionized medium for 64 emission-line field galaxies in the redshift range 0.26<z<0.82. These galaxies comprise a small subset selected from among 693 objects in the DGSS. They are chosen for…
The Nature of Damped Lyα Absorbing Galaxies at z <= 1: A Photometric Redshift Survey of Damped Lyα Absorbers
Chen, Hsiao-Wen; Lanzetta, Kenneth M.
We study the nature of damped Lyα absorption (DLA) systems at z<=1 using a sample of 11 DLA galaxies, for which accurate redshift measurements are available. Five of the 11 systems are identified in our ongoing photometric redshift survey of DLA galaxies, while the remaining six systems are identified by previous groups using either spectroscop…
CO (J=7-->6) Observations of NGC 253: Cosmic-Ray-heated Warm Molecular Gas
Bolatto, A. D.; Stacey, G. J.; Bradford, C. M. +5 more
We report observations of the CO J=7-->6 transition toward the starburst nucleus of NGC 253. This is the highest excitation CO measurement in this source to date and allows an estimate of the molecular gas excitation conditions. Comparison of the CO line intensities with a large velocity gradient, escape probability model indicates that the bul…
Surface brightness profiles and structural parameters for 10 rich stellar clusters in the Small Magellanic Cloud
Mackey, A. D.; Gilmore, G. F.
As a follow-up to our recent study of a large sample of Large Magellanic Cloud (LMC) clusters, we have conducted a similar study of the structures of 10 Small Magellanic Cloud (SMC) clusters, using archival Hubble Space Telescope snapshot data. We present surface brightness profiles for each cluster and derive structural parameters, including core…
Kinetic equilibrium of iron in the atmospheres of cool stars. III. The ionization equilibrium of selected reference stars
Korn, A. J.; Gehren, T.; Shi, J.
Non-LTE line formation calculations of Fe I are performed for a small number of reference stars to investigate and quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravit…
Flaring X-Ray Emission from HST-1, a Knot in the M87 Jet
Sparks, W. B.; Wilson, A. S.; Harris, D. E. +3 more
We present Chandra X-ray monitoring of the M87 jet in 2002, which shows that the intensity of HST-1, an optical knot 0.8" from the core, increased by a factor of 2 in 116 days and a factor of 4 in 2 yr. There was also a significant flux decrease over 2 months, with suggestive evidence for a softening of the spectrum. From this variability behavior…
Study of Ribbon Separation of a Flare Associated with a Quiescent Filament Eruption
Zhang, Hongqi; Qiu, Jiong; Jing, Ju +1 more
In this paper, we present a detailed study of a two-ribbon flare in the plage region observed by Kanzelhohe Solar Observatory (KSO), which is one of the stations in our global Hα network. We select this event due to its very clear filament eruption, two-ribbon separation, and association with a fast coronal mass ejection (CME). We study the separa…