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Inferring Photospheric Velocity Fields Using a Combination of Minimum Energy Fit, Local Correlation Tracking, and Doppler Velocity
Longcope, D. W.; Ravindra, B.; Abbett, W. P.
The minimum energy fit (MEF), a velocity inversion technique, infers all components of the photospheric velocity that are consistent with the induction equation. From the set of consistent velocity fields, it selects the smallest overall flow speed by minimizing a kinetic energy functional. If partial velocity information is available from other m…
Frequencies of wave packets of whistler-mode chorus inside its source region: a case study
Gurnett, D. A.; Pickett, J. S.; Trakhtengerts, V. Y. +5 more
Whistler-mode chorus is a structured wave emission observed in the Earth's magnetosphere in a frequency range from a few hundreds of Hz to several kHz. We investigate wave packets of chorus using high-resolution measurements recorded by the WBD instrument on board the four Cluster spacecraft. A night-side chorus event observed during geomagnetical…
Asteroid 2867 Steins. III. Spitzer Space Telescope observations, size determination, and thermal properties
Jorda, L.; Lamy, P. L.; Barucci, M. A. +6 more
Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008.
Aims: An early characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return.
Methods: We used the infrared spectrograph (IRS) of the Spitzer Space Telescop…
Spectroscopy and multiband photometry of the afterglow of intermediate duration γ-ray burst GRB 040924 and its host galaxy
Hornstrup, A.; Vreeswijk, P. M.; Wijers, R. A. M. J. +19 more
Aims: We present optical photometry and spectroscopy of the afterglow and host galaxy of gamma-ray burst GRB 040924. This GRB had a rather short duration of T90 ~2.4 s, and a well sampled optical afterglow light curve. We aim to use this dataset to find further evidence that this burst is consistent with a massive star core-collapse pro…
A Study of the ρ Ophiuchi Cloud: Mapping the Distribution and the Motions of Interstellar Gas
Welty, Daniel E.; Snow, Theodore P.; Destree, Joshua D.
Guest Investigator results from Hipparcos, combined with high-resolution optical spectra obtained with the Anglo-Australian Observatory, Kitt Peak National Observatory, and McDonald Observatory, are used to create a three-dimensional map of the stars and several interstellar gas components in the ρ Oph cloud complex. Many principal gas components …
A Comparison among Solar Diameter Measurements Carried Out from the Ground and outside Earth's Atmosphere
Thuillier, G.; Djafer, D.; Sofia, S.
The solar diameter has been measured since the 17th century, using different methods and instruments, and without a clear strategy of measurement, which could explain the lack of coherence between the results obtained. The present study confirms that the discrepancies between solar diameter measurements are mostly due to differences in instrumenta…
UV and Radio Observations of the Coronal Shock Associated with the 2002 July 23 Coronal Mass Ejection Event
Mancuso, S.; Avetta, D.
We report on the analysis of a fast coronal mass ejection (CME)-driven shock observed on 2002 July 23 with the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO). The CME was first detected in white light by the Large Angle and Spectrometric Coronagraph Experiment (LASCO), and shock-associated type I…
The serendipituous discovery of a short-period eclipsing polar in 2XMMp
Watson, M. G.; Schwope, A.; Osborne, J. P. +3 more
We report the serendipituous discovery of the new eclipsing polar 2XMMp J131223.4+173659. Its striking X-ray light curve attracted immediate interest when we were visually inspecting the source products of the 2XMMp catalogue. This light curve revealed its likely nature as a magnetic cataclysmic variable of AM Herculis (or polar) type with an orbi…
NGC 602 Environment, Kinematics and Origins
Sabbi, E.; Nota, A.; Gallagher, J. S. +3 more
The young star cluster NGC 602 and its associated HII region, N90, formed in a relatively isolated and diffuse environment in the Wing of the Small Magellanic Cloud. Its isolation from other regions of massive star formation and the relatively simple surrounding HI shell structure allows us to constrain the processes that may have led to its forma…
Validating Time-Distance Far-Side Imaging of Solar Active Regions through Numerical Simulations
Zhao, Junwei; Kosovichev, Alexander G.; Hartlep, Thomas +1 more
Far-side imaging using time-distance helioseismology methods is assessed using numerically generated artificial data. The data are generated using direct numerical simulations of acoustic oscillations in a spherical solar model. Localized variations of the sound speed in the surface and subsurface layers are used to model the perturbations associa…