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Correlated Dynamics of Hot and Cool Plasmas in the Main Phase of a Solar Flare
Wilhelm, K.; Curdt, W.; Dammasch, I. E. +1 more
We report far-ultraviolet observations of a solar limb flare obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer. At a fixed pointing of the slit above the limb, spectra were simultaneously obtained in several emission lines that covered a wide temperature range from ~104 to ~107 K. The te…
Galactic Starburst NGC 3603 from X-Rays to Radio
Ptak, A.; Corcoran, M. F.; Brandner, W. +10 more
NGC 3603 is the most massive and luminous visible starburst region in the Galaxy. We present the first Chandra ACIS-I X-ray image and spectra of this dense, exotic object, accompanied by a deep centimeter-wavelength Australia Telescope Compact Array radio image at similar <~1" spatial resolution and Hubble Space Telescope/ground-based optical d…
Optical Identification of Multiple Faint X-Ray Sources in the Globular Cluster NGC 6752: Evidence for Numerous Cataclysmic Variables
Anderson, Scott F.; Kaspi, Victoria M.; Verbunt, Frank +8 more
We report on the Chandra X-Ray Observatory ACIS-S3 imaging observation of the globular cluster NGC 6752. We detect six X-ray sources within the 10.5" core radius and 13 more within the 115" half-mass radius down to a limiting luminosity of LX~1030 ergs s-1 for cluster sources. We reanalyze archival data from the Hu…
Optical Spectroscopy of Metal-rich H II Regions and Circumnuclear Hot Spots in M83 and NGC 3351
Bresolin, Fabio; Kennicutt, Robert C., Jr.
We present optical spectroscopy of a sample of metal-rich extragalactic H II regions in the spiral galaxies M83 (NGC 5236), NGC 3351, and NGC 6384. The metal abundance, estimated from semiempirical methods using strong emission lines, is found to be above solar for most of the objects. The sample includes a number of circumnuclear H II regions (ho…
A Comparison of Solar p-Mode Parameters from the Michelson Doppler Imager and the Global Oscillation Network Group: Splitting Coefficients and Rotation Inversions
Thompson, M. J.; Howe, R.; Komm, R. +7 more
Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) onboard SOHO, we compare frequency-splitting data and resulting inversions about the Sun's internal rotation. Helioseismology has been very successful in making detailed and subtle inferences about the solar interior. But the…
The Faint Optical Afterglow and Host Galaxy of GRB 020124: Implications for the Nature of Dark Gamma-Ray Bursts
Piro, L.; Axelrod, T. S.; Frontera, F. +24 more
We present ground-based optical observations of GRB 020124 starting 1.6 hr after the burst, as well as subsequent Very Large Array and Hubble Space Telescope (HST) observations. The optical afterglow of GRB 020124 is one of the faintest afterglows detected to date, and it exhibits a relatively rapid decay, Fν~t-1.60+/-0.04, f…
GRB 011121: A Massive Star Progenitor
Wieringa, M. H.; Axelrod, T. S.; Frontera, F. +29 more
Of the cosmological gamma-ray bursts, GRB 011121 has the lowest redshift, z=0.36. More importantly, the multicolor excess in the afterglow detected in the Hubble Space Telescope (HST) light curves is compelling observational evidence of an underlying supernova. Here we present near-infrared and radio observations of the afterglow, and from our com…
Three LINERs under the Chandra X-Ray Microscope
Moran, Edward C.; Shields, Joseph C.; Eracleous, Michael +1 more
We use observations of three galaxies hosting low-ionization nuclear emission-line regions (LINERs; NGC 404, NGC 4736, and NGC 4579) with the Chandra X-Ray Observatory to study their power sources. We find very diverse properties within this small group: NGC 404 has an X-ray faint nucleus with a soft, thermal spectrum; NGC 4736 harbors a plethora …
Flare Activity and Magnetic Helicity Injection by Photospheric Horizontal Motions
Moon, Y. -J.; Wang, Haimin; Yurchyshyn, Vasyl +5 more
We present observational evidence that the occurrence of homologous flares in an active region is physically related to the injection of magnetic helicity by horizontal photospheric motions. We have analyzed a set of 1 minute cadence magnetograms of NOAA AR 8100 taken over a period of 6.5 hr by the Michelson Doppler Imager on board the Solar and H…
Photospheric Motions and Coronal Mass Ejection Productivity
Zhang, H.; Nindos, A.
Shearing motions have been frequently used in MHD simulations of coronal mass ejection (CME) initiation but have hardly been reported from observations of CME-producing regions. In this Letter, we investigate whether the bulk of magnetic helicity carried away from the Sun by CMEs comes from helicity injected to the corona by such motions or by eme…