Search Publications
Magnetic field measurements and wind-line variability of OB-type stars
Rygl, K. L. J.; Neiner, C.; Wiersema, K. +8 more
Context: The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely to be related to such magnetic fields.
Aims: We attempt to improve our understanding of massive-star magne…
Limits on Hot Galactic Halo Gas from X-Ray Absorption Lines
Yao, Y.; Nowak, M. A.; Wang, Q. D. +2 more
Although the existence of large-scale hot gaseous halos around massive disk galaxies has been theorized for a long time, there is yet very little observational evidence. We report the Chandra and XMM-Newton grating spectral detection of O VII and Ne IX Kα absorption lines along the sight line of 4U 1957+11. The line absorption is consistent with t…
Plasma environment of Mars as observed by simultaneous MEX-ASPERA-3 and MEX-MARSIS observations
Barabash, S.; Lundin, R.; Winningham, J. D. +11 more
Simultaneous in situ measurements carried out by the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) and Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instruments on board the Mars Express (MEX) spacecraft for the first time provide us with the local parameters of cold ionospheric and hot solar wind plasma components…
MHD Modeling of Coronal Large-Amplitude Waves Related to CME Lift-off
Vainio, R.; Pomoell, J.; Kissmann, R.
We have employed a two-dimensional magnetohydrodynamic simulation code to study mass motions and large-amplitude coronal waves related to the lift-off of a coronal mass ejection (CME). The eruption of the filament is achieved by an artificial force acting on the plasma inside the flux rope. By varying the magnitude of this force, the reaction of t…
The ACS LCID Project: RR Lyrae Stars as Tracers of Old Population Gradients in the Isolated Dwarf Spheroidal Galaxy Tucana
Skillman, Evan D.; Cole, Andrew A.; Mateo, Mario +9 more
We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous, longer period RR Lyrae variables. Through comparison w…
Coronal Jet Observed by Hinode as the Source of a3He-rich Solar Energetic Particle Event
Krucker, Säm; Shibata, Kazunari; Nitta, Nariaki V. +5 more
We study the solar source of the 3He-rich solar energetic particle (SEP) event observed on 2006 November 18. The SEP event showed a clear velocity dispersion at energies below 1 MeV nucleon-1, indicating its solar origin. We associate the SEP event with a coronal jet in an active region at heliographic longitude of W50°, as o…
Composition of the Venus mesosphere measured by Solar Occultation at Infrared on board Venus Express
Vandaele, A. C.; Montmessin, F.; Fedorova, A. +8 more
Solar Occultation at Infrared (SOIR), which is a part of the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument on board Venus Express, combines an echelle-grating spectrometer with an acoustooptical tunable filter. It performs solar occultation measurements in the IR region at a high spectral resoluti…
Weighing the Quiescent Central Black Hole in an Elliptical Galaxy with X-Ray-Emitting Gas
Gebhardt, Karl; Humphrey, Philip J.; Buote, David A. +2 more
We present a Chandra study of the hot interstellar medium (ISM) in the giant elliptical galaxy NGC 4649. In common with other group-centered ellipticals, its temperature profile rises with radius in the outer parts of the galaxy, from ~0.7 keV at 2 kpc to ~0.9 keV by 20 kpc. However, within the central ~2 kpc the trend reverses, and the temperatur…
The secrets of T Pyxidis. II. A recurrent nova that will not become a SN Ia
Selvelli, P.; González-Riestra, R.; Gilmozzi, R. +1 more
Aims: We compare the observed and theoretical parameters for the quiescent and outburst phases of the recurring nova T Pyx.
Methods: IUE data were used to derive the disk luminosity and the mass accretion rate, and to exclude the presence of quasi-steady burning at the WD surface. XMM-NEWTON data were used to verify this conclusion.
Result…
Venus upper atmospheric CO, temperature, and winds across the afternoon/evening terminator from June 2007 JCMT sub-millimeter line observations
Clancy, R. T.; Sandor, B. J.; Moriarty-Schieven, G. H.
The Venus mesosphere constitutes a highly variable transition region between the zonal rotation of the lower atmosphere and the diurnal circulation of the upper atmosphere. It further serves as the primary photochemical region of the Venus atmosphere. We obtained James Clerk Maxwell Telescope (JCMT, Mauna Kea Hawaii) sub-millimeter line observatio…