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Hot Coronal Loop Oscillations Observed by SUMER: Slow Magnetosonic Wave Damping by Thermal Conduction
Ofman, L.; Wang, Tongjiang
Recently, strongly damped Doppler shift oscillations of hot (T>6 MK) coronal loops were observed with the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory. The oscillations are interpreted as signatures of slow-mode magnetosonic waves excited impulsively in the loops. Using …
Solar Phenomena Associated with ``EIT Waves''
Thompson, B. J.; Biesecker, D. A.; Vourlidas, A. +2 more
In an effort to understand what an ``EIT wave'' is and what its causes are, we have looked for correlations between the initiation of EIT waves and the occurrence of other solar phenomena. An EIT wave is a coronal disturbance, typically appearing as a diffuse brightening propagating across the Sun. A catalog of EIT waves, covering the period from …
Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona
Kusano, K.; Sakurai, T.; Yokoyama, T. +1 more
We develop a new methodology that can determine magnetic helicity flux as well as Poynting flux across the photosphere based on magnetograph observation. By applying this method, we study the injection mechanism of magnetic helicity and magnetic free energy into the solar corona. In order to derive the helicity and energy fluxes, first the velocit…
Toward a Mass and Radius Determination of the Nearby Isolated Neutron Star RX J185635-3754
Walter, Frederick M.; Neuhäuser, Ralph; Lattimer, James M. +3 more
We discuss efforts to determine the mass, radius, and surface composition of the nearby compact object RX J185635-3754 from its multiwavelength spectral energy distribution. We compute nonmagnetized model atmospheres and emergent spectra for selected compositions and gravities and discuss efforts to fit existing and new observational data from ROS…
Large-Amplitude X-Ray Outbursts from Galactic Nuclei: A Systematic Survey using ROSAT Archival Data
Brandt, W. N.; Eracleous, Michael; Boller, Th. +1 more
In recent years, luminous X-ray outbursts with variability amplitudes as high as ~400 have been serendipitously detected from a small number of active and inactive galaxies. These outbursts may result from the tidal disruptions of stars by supermassive black holes, as well as accretion disk instabilities. In order to place the first reliable const…
The Luminosity Function of Star Clusters in Spiral Galaxies
Larsen, Søren S.
Star clusters in six nearby spiral galaxies are examined using archive images from the Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST). The galaxies have previously been studied from the ground and some of them are known to possess rich populations of ``young massive clusters.'' Comparison with the HST images indica…
Mid-Infrared line diagnostics of active galaxies. A spectroscopic AGN survey with ISO-SWS
Lutz, D.; Genzel, R.; Sturm, E. +5 more
We present medium resolution (R ~ 1500) ISO-SWS 2.4-45 mu m spectra of a sample of 29 galaxies with active nuclei. This data set is rich in fine structure emission lines tracing the narrow line regions and (circum-)nuclear star formation regions, and it provides a coherent spectroscopic reference for future extragalactic studies in the mid-infrare…
Coronal Holes and the High-Speed Solar Wind
Cranmer, Steven R.
Coronal holes are the lowest density plasma components of the Sun's outer atmosphere, and are associated with rapidly expanding magnetic fields and the acceleration of the high-speed solar wind. Spectroscopic and polarimetric observations of the extended corona, coupled with interplanetary particle and radio sounding measurements going back severa…
Doppler Shift Oscillations of Hot Solar Coronal Plasma Seen by SUMER: A Signature of Loop Oscillations?
Solanki, S. K.; Curdt, W.; Innes, D. E. +2 more
We report observations of strongly damped Doppler shift oscillations detected in a flare line, Fe XIX, with the Solar Ultraviolet Measurement of Emitted Radiation spectrometer. Spectra were recorded above an active region at the western limb of the Sun, from lines with formation temperatures ranging from 0.01 to 10 MK. However, the oscillations we…
Hubble Space Telescope and Chandra Monitoring of the Crab Synchrotron Nebula
Gallagher, J. S.; Mori, K.; Hester, J. J. +6 more
We report the results of coordinated Hubble Space Telescope and Chandra observations of the Crab synchrotron nebula. Similar dynamical structures, including equatorial wisps moving outward at ~0.5c, are seen in both passbands. The inner X-ray ring is a variable, irregular structure from which wisps and diffuse emission emerge. The X-ray/visible je…