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Constraints on Active Region Coronal Heating
Golub, L.; Antiochos, S. K.; DeLuca, E. E. +2 more
We derive constraints on the time variability of coronal heating from observations of the so-called active region moss by the Transition Region and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees…
Helicity Evolution in Emerging Active Regions
Pevtsov, Alexei A.; Maleev, Vasily M.; Longcope, Dana W.
We study the evolution of twist and magnetic helicity in the coronal fields of active regions as they emerge. We use multiday sequences of Solar and Heliospheric Observatory Michelson Doppler Interferometer magnetograms to characterize the region's emergence. We quantify the overall twist in the coronal field, α, by matching a linear force-free fi…
Empirically Determined Anisotropic Velocity Distributions and Outflows of O5+ Ions in a Coronal Streamer at Solar Minimum
Cranmer, S. R.; Kohl, J. L.; Frazin, R. A.
Empirical constraints on the O5+ velocity distributions and outflow speeds in a solar minimum equatorial streamer between 2.6 and 5.1 Rsolar are determined using a spectral synthesis code that includes O VI Doppler dimming. These constraints follow directly from UV spectra taken on 1996 October 12 with the Ultraviolet Coronag…
Imaging polarimetry of cometary dust: different comets and phase angles
Levasseur-Regourd, A. C.; Hadamcik, E.
Polarimetric observations of the light scattered by dust in cometary comae have been carried out at Pic-du-Midi Observatory and at Haute-Provence Observatory (France) between 1990 and 2001. The whole coma polarization can easily be inferred from integration of the fluxes on the aperture. Maps are obtained for seven comets by CCD imaging polarimetr…
Hubble Space Telescope Detection of Spiral Structure in Two Coma Cluster Dwarf Galaxies
Jerjen, Helmut; Graham, Alister W.; Guzmán, Rafael
We report the discovery of spiral-like structure in Hubble Space Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the Coma Cluster. GMP 3629 is the faintest such galaxy detected in a cluster environment, and it is the first such galaxy observed in the dense Coma Cluster. The large bulge and the faintness of the broad spi…
Nearby young stars
Schmitt, J. H. M. M.; Hubrig, S.; Wichmann, R.
We present the results of an extensive all-sky survey of nearby stars of spectral type F8 or later in a systematic search of young (zero-age main sequence) objects. Our sample has been derived by cross-correlating the ROSAT All-Sky Survey and the TYCHO catalogue, yielding a total of 754 candidates distributed more or less randomly over the sky. Fo…
The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey and the Rest-Frame R-Band Galaxy Luminosity Function at 0.5<=z<=1.5
McCarthy, Patrick J.; Martini, P.; Chen, Hsiao-Wen +6 more
We present rest-frame, R-band, galaxy luminosity function measurements for three different redshift ranges: 0.5<=z<=0.75, 0.75<=z<=1.0, and 1.0<=z<=1.5. Our measurements are based on photometric redshifts for ~3000 H-band-selected galaxies with apparent magnitudes 17<=H<=20 from the Las Campanas Infrared Survey. We show tha…
The mass and energy budget of Cassiopeia A
Kaastra, J. S.; Bleeker, J. A. M.; Willingale, R. +1 more
Further analysis of X-ray spectroscopy results (Willingale et al. \cite{Wil02}) recently obtained from the MOS CCD cameras on-board XMM-Newton provides a detailed description of the hot and cool X-ray emitting plasma in Cas A. Measurement of the Doppler broadening of the X-ray emission lines is consistent with the expected ion velocities, ~ 1500 k…
The Role of Polycyclic Aromatic Hydrocarbons in Ultraviolet Extinction. I. Probing Small Molecular Polycyclic Aromatic Hydrocarbons
Gordon, Karl D.; Witt, A. N.; Whittet, D. C. B. +6 more
We have obtained new Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra to search for structure in the ultraviolet interstellar extinction curve, with particular emphasis on a search for absorption features produced by polycyclic aromatic hydrocarbons (PAHs). The presence of these molecules in the interstellar medium has been post…
Discovery of a quiescent neutron star binary in the globular cluster M 13
Barret, D.; Webb, N.; Gendre, B.
We have discovered with XMM-Newton an X-ray source in the core of the globular cluster M 13, whose X-ray spectral properties suggest that it is a quiescent neutron star X-ray binary. The spectrum can be well fitted with a pure hydrogen atmosphere model, with Tinfty =76+/-3 eV, Rinfty =12.8+/-0.4 km and an X-ray luminosity of …