Search Publications
Morpho-kinematic Analysis of the Point-symmetric, Bipolar Planetary Nebulae Hb 5 and K 3-17, A Pathway to Poly-polarity
López, J. A.; Steffen, W.; García-Díaz, Ma. T. +2 more
The kinematics of the bipolar planetary nebulae Hb 5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry, and very fast bipolar o…
Dwarf galaxies in the Coma cluster - I. Velocity dispersion measurements
Mobasher, B.; Tully, R. B.; Guzmán, R. +8 more
We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magn…
'Distance mapping' and the 3D structure of BD +30° 3639
Akras, S.; Steffen, W.
BD +30° 3639 is a member of a group of uncommon planetary nebulae with Wolf-Rayet central star and higher expansion velocities in [O III] than in [N II] lines. Images and high-resolution spectra from the literature are used in order to construct a 3D model of the nebula using the morpho-kinematic code SHAPE. We find that two homologous expansion l…
X-Ray Spectral Variability in NGC 3783
Fabian, A. C.; Miller, J. M.; Reynolds, C. S. +6 more
NGC 3783 was observed for approximately 210 ks by Suzaku and in this time showed significant spectral and flux variability at both short (20 ks) and long (100 ks) timescales. The full observation is found to consist of approximately six "spectral periods" where the behavior of the soft (0.3-1.0 keV) and hard (2-10 keV) bands are somewhat distinct.…
Seasonal and clock angle control of the location of flux transfer event signatures at the magnetopause
Milan, S. E.; Fear, R. C.; Palmroth, M.
Most models of flux transfer event (FTE) formation produce pairs of structures which in general move away from the subsolar region and give rise to signatures which can be observed in both the Northern and Southern Hemispheres. The multiple reconnection line (X line) model is unusual as a reconnection-based model that is capable of producing a sin…
Revised and updated catalogue of the First Byurakan Survey of late-type stars
Gigoyan, K. S.; Mickaelian, A. M.
There have been 15 lists of late-type stars published between 1990 and 2010. These late-type stars have been found in the low-dispersion spectroscopic plates of the First Byurakan Survey (FBS). The systematic search and selection was carried out on a surface ∼16 000 deg2 on almost the whole area of the FBS. As a result, a comprehensive …
Accurate classification of 29 objects detected in the 39 month Palermo Swift/BAT hard X-ray catalogue
Palazzi, E.; Minniti, D.; Masetti, N. +15 more
Through an optical campaign performed at four telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift /Burst Alert Telescope (BAT) and listed in the 39 mont…
Joint spectral-timing modelling of the hard lags in GX 339-4: constraints on reflection models
Wilms, J.; Uttley, P.; Cassatella, P. +1 more
The X-ray variations of hard state black hole X-ray binaries above 2 keV show 'hard lags', in that the variations at harder energies follow variations at softer energies, with a time lag τ depending on frequency ν approximately as τ∝ν-0.7. Several models have so far been proposed to explain this time delay, including fluctuations propag…
Formation, shape, and evolution of magnetic structures in CIRs at 1 AU
McComas, D. J.; Desai, M. I.; Broiles, T. W.
We have surveyed the properties of 153 co-rotating interaction regions (CIRs) observed at 1 AU from January, 1995 through December, 2008. We identified that 74 of the 153 CIRs contain planar magnetic structures (PMSs). For planar and non-planar CIRs, we compared distributions of the bulk plasma and magnetic field parameters. Our identification of …
Triaxiality, principal axis orientation and non-thermal pressure in Abell 383
Limousin, Marceau; Morandi, Andrea
While clusters of galaxies are regarded as one of the most important cosmological probes, the conventional spherical modelling of the intracluster medium and the dark matter (DM), and the assumption of strict hydrostatic equilibrium (i.e. the equilibrium gas pressure is provided entirely by thermal pressure) are very approximate at best. Extending…