Search Publications
Validated helioseismic inversions for 3D vector flows
Hanasoge, S. M.; Gizon, L.; Švanda, M. +1 more
Context. According to time-distance helioseismology, information about internal fluid motions is encoded in the travel times of solar waves. The inverse problem consists of inferring three-dimensional vector flows from a set of travel-time measurements. While only few tests of the inversions have been done, it is known that the retrieval of the sm…
New Evidence for High Activity of the Supermassive Black Hole in our Galaxy
Koyama, K.; Nobukawa, M.; Tsuru, T. G. +1 more
Prominent K-shell emission lines of neutral iron (hereafter Fe I-K lines) and hard-continuum X-rays from molecular clouds (MCs) in the Sagittarius B (Sgr B) region were found in two separate Suzaku observations in 2005 and 2009. The X-ray flux of the Fe I-K lines decreased in correlation with the hard-continuum flux by a factor of 0.4-0.5 in four …
Spatially resolved kinematics of an ultracompact dwarf galaxy
Infante, L.; Grebel, E. K.; Hilker, M. +3 more
We present the internal kinematics of UCD3, the brightest known ultracompact dwarf galaxy (UCD) in the Fornax cluster, making this the first UCD with spatially resolved spectroscopy. Our study is based on seeing-limited observations obtained with the ARGUS Integral Field Unit of the VLT/FLAMES spectrograph under excellent seeing conditions (0.5-0.…
Continuous upflows and sporadic downflows observed in active regions
Peter, H.; Solanki, S. K.; Curdt, W. +1 more
Aims: We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops.
Methods: We analyzed images of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at multiple temperatures to detect apparent motions in the coronal loops.
Results:…
An analytic model for blue straggler formation in globular clusters
Sills, Alison; Knigge, Christian; Leigh, Nathan
We present an analytic model for blue straggler formation in globular clusters. We assume that blue stragglers are formed only through stellar collisions and binary star evolution, and compare our predictions to observed blue straggler numbers. We can summarize our key results as follows. (1) Binary star evolution consistently dominates blue strag…
Rotational dynamics and internal structure of Titan
Nimmo, Francis; Bills, Bruce G.
Estimates of the moments of inertia of Titan, as separately deduced from its gravitational field and spin pole orientation, are quite different. This discrepancy can be resolved if Titan is either not precessing as a rigid body (e.g. if the shell is decoupled from the interior by an ocean), or if the spin pole is not fully damped (e.g. due to atmo…
Turbulent and fast motions of H2 gas in active galactic nuclei
Combes, F.; Dasyra, K. M.
Querying the Spitzer archive for optically-selected active galactic nuclei (AGN) observed in high-resolution-mode spectroscopy, we identified radio and/or interacting galaxies with highly turbulent motions of H2 gas at a temperature of a few hundred Kelvin. Unlike all other AGN that have unresolved H2 line profiles at a spect…
On the nature of particle energization via resonant wave-particle interaction in the inhomogeneous magnetospheric plasma
Shklyar, D. R.
When a quasi-monochromatic wave propagating in an inhomogeneous magnetoplasma has sufficiently large amplitude, there exist phase-trapped resonant particles whose energy increases or decreases depending on the "sign" of inhomogeneity. The variation of energy density of such particles can greatly exceed the wave energy density which contradicts ene…
Spectroscopic evidence for helicity in explosive events
Curdt, W.; Tian, H.
Aims: We report spectroscopic observations in support of a novel view of transition region explosive events, observations that lend empirical evidence that at least in some cases explosive events may be nothing else but spinning narrow spicule-like structures.
Methods: Our spectra of textbook explosive events with simultaneous Doppler fl…
Response of Saturn's auroral ionosphere to electron precipitation: Electron density, electron temperature, and electrical conductivity
Galand, Marina; Moore, Luke; Miller, Steve +2 more
In the high-latitude regions of Saturn, the ionosphere is strongly coupled to the magnetosphere through the exchange of energy. The influx of energetic particles from Saturn's magnetosphere enhances the ionospheric densities and temperatures, affects the electrodynamical properties of the ionosphere, and contributes to the heating of the thermosph…