Search Publications
A High-Resolution X-Ray Image of the Jet in M87
Davis, D. S.; Marshall, H. L.; Harris, D. E. +4 more
We present the first high-resolution X-ray image of the jet in M87 using the Chandra X-Ray Observatory. There is clear structure in the jet and almost all of the optically bright knots are detected individually. The unresolved core is the brightest X-ray feature but is only 2-3 times brighter than knot A (12.3" from the core) and the inner knot HS…
Reducing heliospheric magnetic flux from coronal mass ejections without disconnection
Crooker, N. U.; Gosling, J. T.; Kahler, S. W.
Until 1995, disconnection at the Sun was thought to be the only solution to the problem of balancing the magnetic flux coronal mass ejections (CMEs) added to the heliosphere, in spite of the fact that the expected solar wind signature of disconnection was rare. Disconnection was pictured as merging between open field lines to create completely dis…
Far-Infrared Galaxies in the Far-Ultraviolet
Sanders, D. B.; Steidel, Charles C.; Heckman, Timothy M. +4 more
In an effort to better understand the UV properties of ultraluminous infrared galaxies (ULIGs), and compare them to the rest-frame UV properties of high redshift submillimeter and Lyman-break galaxies, we have obtained far- and near-UV imaging observations (λeff=1457 and 2364 Å, respectively) of two luminous infrared galaxies (LIGs-VV 1…
Revised Stellar Temperatures for Magellanic Cloud O Supergiants from Far Ultraviolet Spectroscopic Explorer and Very Large Telescope UV-Visual Echelle Spectrograph Spectroscopy
Hillier, D. J.; Crowther, P. A.; Willis, A. J. +3 more
We have undertaken quantitative analysis of four LMC and SMC O4-9.7 extreme supergiants using far-ultraviolet FUSE, ultraviolet IUE/Hubble Space Telescope, and optical Very Large Telescope UV-Visual Echelle Spectrograph spectroscopy. Extended, non-LTE model atmospheres that allow for the consistent treatment of line blanketing, developed by Hillie…
New periodic variables from the Hipparcos epoch photometry
Koen, Chris; Eyer, Laurent
Two selection statistics are used to extract new candidate periodic variables from the epoch photometry of the Hipparcos catalogue. The primary selection criterion is a signal-to-noise ratio. The dependence of this statistic on the number of observations is calibrated using about 30000 randomly permuted Hipparcos data sets. A significance level of…
What is the source of the magnetic helicity shed by CMEs? The long-term helicity budget of AR 7978
Thompson, B. J.; Mandrini, C. H.; van Driel-Gesztelyi, L. +5 more
An isolated active region (AR) was observed on the Sun during seven rotations, starting from its birth in July 1996 to its full dispersion in December 1996. We analyse the long-term budget of the AR relative magnetic helicity. Firstly, we calculate the helicity injected by differential rotation at the photospheric level using MDI/SoHO magnetograms…
The Tycho double star catalogue
Makarov, V. V.; Fabricius, C.; Urban, S. E. +3 more
We report the discovery of 13 251 visual double stars, mostly with separations between 0.3 and 1 arcsec, from a dedicated re-reduction of the Tycho data from the star mapper of the ESA Hipparcos satellite. The new doubles are combined with 18 160 WDS systems identified in the Tycho-2two, and 1220 new Tycho-2 doubles, to form the Tycho Double Star …
A Statistical Study of Two Classes of Coronal Mass Ejections
Moon, Y. -J.; Yang, Guo; Wang, Haimin +4 more
A comprehensive statistical study is performed to address the question of whether two classes of coronal mass ejections (CMEs) exist. A total of 3217 CME events observed by SOHO/LASCO in 1996-2000 have been analyzed. We have examined the distributions of CMEs according to speed and acceleration, respectively, and investigated the correlation betwe…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A 13 Year Study of Spectral Variability in NGC 5548
Filippenko, A. V.; Shapovalova, A. I.; Chavushyan, V. H. +38 more
We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hβ emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hβ measurements. The Hβ variations follow the continuum variations closely, with a typical time delay of about 20 da…
Stellar and wind properties of LMC WC4 stars. A metallicity dependence for Wolf-Rayet mass-loss rates
Hillier, D. J.; Crowther, P. A.; Fullerton, A. W. +2 more
We use ultraviolet space-based (FUSE, HST) and optical/IR ground-based (2.3 m MSSSO, NTT) spectroscopy to determine the physical parameters of six WC4-type Wolf-Rayet stars in the Large Magellanic Cloud. Stellar parameters are revised significantly relative to Gräfener et al. (\cite{Grafener1998}) based on improved observations and more sophistica…