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The Ringed Spiral Galaxy NGC4622. II. An Independent Determination that the Two Outer Arms Lead
Byrd, Gene G.; Freeman, Tarsh; Buta, Ronald J. +1 more
The spiral galaxy NGC4622 was recognized by Byrd et al. (1989, Celest. Mech., 45, 31) to have a single inner arm winding outward counterclockwise (CCW) and an outer pair of arms winding outward clockwise (CW). Using HST and ground-based observations, Buta et al. (2003, AJ, 125, 634) used a dust silhouette method to determine that the disk of NGC46…
The Curlometer and Other Gradient Based Methods
Eastwood, Jonathan P.; Dunlop, Malcolm W.
The magnetic field measurements on the four Cluster spacecraft can be combined to produce a determination of the electric current density, j, point by point in time, from Ampere's law, i.e., through an estimate of the curl of the magnetic field, B, assuming the displacement current may be neglected (an assumption nearly always true in space plasma…
Ground-based variability surveys towards Centaurus A: worthwhile or not?
Héraudeau, P.; de Jong, J. T. A.; Kuijken, K. H.
Context: Difference imaging has proven to be a powerful technique for detecting and monitoring the variability of unresolved stellar sources in M 31. Using this technique in surveys of galaxies outside the Local Group could have many interesting applications.
Aims: The goal of this paper is to test difference imaging photometry on Centaurus A,…
Radiance and Doppler shift distributions across the network of the quiet Sun
Tu, C. -Y.; Tian, H.; He, J. -S. +1 more
Aims: The radiance and Doppler-shift distributions across the solar network provide observational constraints of two-dimensional modeling of transition-region emission and flows in coronal funnels. These distributions have not, however, been studied in detail and we attempt an investigation for a quiet Sun region.
Methods: Two different method…
Orientation of the hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 ephemerides based on asteroid observations
Chernetenko, Yu. A.
Highly accurate observations of 116 asteroids are used to determine the orientation of the Hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 majorplanet ephemerides. These observations include the photographic observations of 15 asteroids obtained as part of the programs for observing selected asteroids and re…
The complex galaxy cluster Abell 514: New results obtained with the XMM-Newton satellite
Schindler, S.; Gitti, M.; Dolag, K. +1 more
Aims: We study the X-ray morphology and dynamics of the galaxy cluster Abell 514. Also, the relation between the X-ray properties and Faraday Rotation measures of this cluster are investigated in order to study the connection of magnetic fields and the intra-cluster medium.
Methods: We use two combined XMM-Newton pointings that are split into …
A Systematic Survey of H I Lyα and O VI Doublet Profiles Observed in Polar Coronal Holes at Solar Minimum
Nakagawa, Akinari
A systematic, comprehensive survey of H I Lyα and O VI doublet profiles in polar coronal holes is performed using spectroscopic observation by the SOHO Ultraviolet Coronagraph Spectrometer (UVCS) at solar minimum in 1996-1997. By decomposing coronal hole profiles into component Gaussians, we determine detailed height distributions of profile param…
The unusual UV continuum of quasar Ton 34 and the possibility of crystalline dust absorption
Binette, L.; Krongold, Y.
Context: Luminous quasars are known to display a sharp steepening of the continuum near 1100 Å. This spectral feature is not well fitted by current accretion disk models, unless Comptonization of the disk emission is invoked. Absorption by carbon crystalline dust has been proposed to account for this feature.
Aims: Ton 34 (zq = 1.92…
Dissecting the star formation history of starburst galaxies: the case of NGC 7673
Pasquali, A.; Castangia, P.
We have collected archival data on NGC 7673 to constrain the star formation history that produced the young star clusters and the field stellar population in this galaxy during the last 2 Gyr. We have considered the sample of 50 star clusters detected by Hubble Space Telescope/WFPC2 in the UV,V and I bands and estimated their age, intrinsic redden…
The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars
Zhang, Ke; Jiang, Biwei
The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the c…