Search Publications
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…
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…
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…
Isotopic Ratios in Titan's Atmosphere from Cassini CIRS Limb Sounding: HC3N in the North
Irwin, P. G. J.; Teanby, N. A.; Flasar, F. M. +8 more
This Letter reports the first detection of the three 13C isotopologues of HC3N on Titan, from Cassini Composite Infrared Spectrometer (CIRS) infrared spectra. The data are limb spectra taken at latitudes N54°-N69° in 2006 and 2007 when HC3N was enhanced in the north. Using a new line list for the ν5 band…
Low-Frequency Lyα Power Spectra Observed by UVCS in a Polar Coronal Hole
Bemporad, A.; Poletto, G.; Matthaeus, W. H.
The occurrence of f-1 noise in interplanetary magnetic fields (in the 1 × 10-5 to 1 × 10-4 Hz band) and other plasma parameters has now been known for about 20 years and has been recently identified also in the photospheric magnetic fields. However, the relationship between interplanetary and solar fluctuation spec…
A Kiloparsec-Scale X-Ray Jet in the BL Lac Source S5 2007+777
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +2 more
X-ray jets in AGNs are commonly observed in FR II and FR I radio galaxies, but rarely in BL Lac objects, most probably due to their orientation close to the line of sight and the ensuing foreshortening effects. Only three BL Lac objects are known so far to contain a kpc-scale X-ray jet. In this paper we present the evidence for the existence of a …
Exploratory Study of the X-Ray Properties of Quasars with Intrinsic Narrow Absorption Lines
Charlton, Jane C.; Eracleous, Michael; Misawa, Toru +1 more
We have used archival Chandra and XMM-Newton observations of quasars hosting intrinsic narrow UV absorption lines (intrinsic NALs) to carry out an exploratory survey of their X-ray properties. Our sample consists of three intrinsic NAL quasars and one "mini-BAL" quasar, plus four quasars without intrinsic absorption lines for comparison. These wer…
Lensing Probabilities for Spectroscopically Selected Galaxy-Galaxy Strong Lenses
Keeton, Charles R.; Dobler, Gregory; Bolton, Adam S. +1 more
Spectroscopic galaxy-galaxy lens searches are presently the most prolific method of identifying strong lens systems in large data sets. We study the probabilities associated with these lens searches, namely the probability of identifying a candidate with rogue [O II] emission lines in a galaxy's spectrum, and the probability that the candidate wil…