Search Publications
The Complex Neutral Gas Dynamics of the Dwarf Starburst Galaxy NGC 625
Cannon, John M.; Skillman, Evan D.; McClure-Griffiths, N. M. +1 more
We present new multiconfiguration H I aperture synthesis imaging of the nearby dwarf starburst galaxy NGC 625 obtained with the Australia Telescope Compact Array. Total H I column density images show gas well aligned with the optical major axis and low column density H I extending to greater than 6 optical scale lengths. The H I velocity field, on…
The Spectral Energy Distribution and Emission-Line Properties of the Narrow-Line Seyfert 1 Galaxy Arakelian 564
Brandt, W. N.; Kriss, G. A.; Turner, T. J. +11 more
We present the intrinsic spectral energy distribution (SED) of the narrow-line Seyfert 1 galaxy (NLS1) Ark 564, constructed with contemporaneous data obtained during a multiwavelength, multisatellite observing campaign in 2000 and 2001. We compare this SED with that of the NLS1 Ton S180 and with those obtained for broad-line Seyfert 1 galaxies to …
Hubble Space Telescope WFPC2 Study of the Trapezium Cluster: The Influence of Circumstellar Disks on the Initial Mass Function
Panagia, N.; Robberto, M.; Song, J. +3 more
We have performed the first measures of mass accretion rates in the core of the Orion Nebula Cluster. Four adjacent fields centered on the Trapezium stars have been imaged in the U and B bands using the Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. We obtained photometry for 91 stars in the U band (F336W) and 71 stars …
Discovery of a Dwarf Poststarburst Galaxy near a High Column Density Local Lyα Absorber
Stocke, John T.; Keeney, Brian A.; Giroux, Mark L. +3 more
We report the discovery of a dwarf (MB=-13.9) poststarburst galaxy coincident in recession velocity (within uncertainties) with the highest column density absorber (NHI=1015.85 cm-2 at cz=1586 km s- 1) in the 3C 273 sight line. This galaxy is by far the closest galaxy to this absorber, project…
A Study of a Tiny Two-Ribbon Flare Driven by Emerging Flux
Shibata, Kazunari; Akiyama, Sachiko; Brooks, David H. +6 more
We present observations of the eruption of a miniature filament that occurred near NOAA Active Region 9537 on 2001 July 14. The eruption was observed by the Hida Observatory Domeless Solar Telescope, in the Hα line center and +/-0.4 Å wings, the Solar and Heliospheric Observatory EUV Imaging Telescope (EIT) and Michelson Doppler Imager, and the Yo…
The Effective Temperatures of Hot Stars. II. The Early-O Types
Bianchi, Luciana; Garcia, Miriam
We derived the stellar parameters of a sample of Galactic early-O type stars by analyzing their UV and far-UV spectra from the Far Ultraviolet Spectroscopic Explorer (905-1187 Å), the International Ultraviolet Explorer, the Hubble Space Telescope STIS, and the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer (1200-2000 Å). The dat…
Ultralow Iron Abundances in the Distant Hot Gas in Galaxy Groups
Buote, David A.; Brighenti, Fabrizio; Mathews, William G.
A new XMM observation of the outer regions of the galaxy group NGC 5044 indicates hot gas iron abundances of only ZFe/Zsolar~0.15 between r=0.2rvir and 0.4rvir. While the total baryon mass within the virial radius may be close to the cosmic mean value observed in rich clusters, the ratio of total iron ma…
Does Solar Structure Vary with Solar Magnetic Activity?
Basu, Sarbani; Mandel, Anna
We present evidence that solar structure changes with changes in solar activity. We find that the adiabatic index, Γ1, changes near the second helium ionization, i.e., at a depth of about 0.98 Rsolar. We believe that this change is a result of the change in the effective equation of state caused by magnetic fields. Inversions…
Coronal Loop Oscillations and Flare Shock Waves
Hudson, H. S.; Warmuth, A.
A statistical analysis of coronal loop oscillations observed by the Transition Region and Coronal Explorer (TRACE) shows that 12 of 28 cases were associated with metric type II bursts. The timing is consistent with the idea that in many cases the loop oscillations result from the passage of a large-scale wave disturbance originating in a flare in …
Chromospheric Waves Observed in the He I Spectral Line (λ = 10830 Å): A Closer Look
Gilbert, Holly R.; Holzer, Thomas E.
Although ``Moreton'' waves have historically been observed in Hα data, more recently waves have also been observed in chromospheric He I (λ=10830 Å) images. In a previous study, we found that chromospheric waves observed in He I data (from the Mauna Loa Solar Observatory) in two events (occurring on 2000 November 25 and 2001 January 20) are cospat…