Search Publications
Identification of iron sulphide grains in protoplanetary disks
Waters, L. B. F. M.; Mutschke, H.; Henning, T. +8 more
Sulphur is depleted in cold dense molecular clouds with embedded young stellar objects, indicating that most of it probably resides in solid grains. Iron sulphide grains are the main sulphur species in cometary dust particles, but there has been no direct evidence for FeS in astronomical sources, which poses a considerable problem, because sulphur…
On the intensity contrast of solar photospheric faculae and network elements
Solanki, S. K.; Sanahuja, B.; Ortiz, A. +2 more
Sunspots, faculae and the magnetic network contribute to solar irradiance variations. The contribution due to faculae and the network is of basic importance, but suffers from considerable uncertainty. We determine the contrasts of active region faculae and the network, both as a function of heliocentric angle and magnetogram signal. To achieve thi…
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…
3D Coronal magnetic field from vector magnetograms: non-constant-alpha force-free configuration of the active region NOAA 8151
Amari, T.; Régnier, S.; Kersalé, E.
The Active Region 8151 (AR 8151) observed in February 1998 is the site of an eruptive event associated with a filament and a S-shaped structure, and producing a slow Coronal Mass Ejection (CME). In order to determine how the CME occurs, we compute the 3D coronal magnetic field and we derive some relevant parameters such as the free magnetic energy…
The Structure of the Local Interstellar Medium. I. High-Resolution Observations of Fe II, Mg II, and Ca II toward Stars within 100 Parsecs
Redfield, Seth; Linsky, Jeffrey L.
High-resolution absorption measurements (λ/Δλ>~100,000) of the resonance lines of Fe II, Mg II, and Ca II are presented for all available observed targets within 100 pc. The Fe II and Mg II spectra were obtained with the Goddard High Resolution Spectrograph (GHRS) and the Space Telescope Imaging Spectrograph (STIS) instruments aboard the Hubble…
Ultra-relativistic electrons in Jupiter's radiation belts
Johnson, W. T. K.; Klein, M.; Hofstadter, M. +18 more
Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for elect…
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…
New High Proper Motion Stars from the Digitized Sky Survey. I. Northern Stars with 0.5" yr-1<µ<2.0" yr-1 at Low Galactic Latitudes
Lépine, Sébastien; Rich, R. Michael; Shara, Michael M.
We have conducted a systematic search for high proper motion stars in the Digitized Sky Survey, in the area of the sky north of -2.8 degrees in declination and within 25 degrees of the Galactic plane. Using the SUPERBLINK software, a powerful automated blink comparator developed by us, we have identified 601 stars in the magnitude range 9<r<…
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…