Search Publications
Coronal Radiation and Helium λ584 Emission in Active Regions
Fredvik, T.; Maltby, P.
Based on EUV observations of eleven sunspot regions obtained with the Coronal Diagnostic Spectrometer, CDS, on SOHO we have studied the spatial distribution, temporal variation and wavelength shift of the He i λ584 line. We find a relatively high spatial correlation between the coronal line Fe xvi λ360 and the He i λ584 line. This points to corona…
Transient Infall Events in the Disk of AB Aurigae: The β Pictoris Phenomenon at 2-4 Megayears
Massa, D.; Grady, C. A.; Bjorkman, K. S. +1 more
Surveys of Herbig Ae/Be stars have indicated that infalling, circumstellar gas similar to that routinely detected toward β Pic is preferentially observed close to the disk midplane. Recent millimeter interferometry of the historically prototypical Herbig Ae star, AB Aur, indicates that this star is viewed slightly above the disk midplane (i=76
Mapping the gas kinematics and ionization structure of four ultraluminous IRAS galaxies
Abraham, R. G.; Crawford, C. S.; Wilman, R. J.
We present a study of the morphology, kinematics and ionization structure of the extended emission-line regions in four intermediate-redshift (0.118<z<0.181) ultraluminous infrared galaxies, derived from ARGUS two-dimensional fibre spectroscopy. The gas kinematics in the hyperluminous system IRAS F20460+1925 lack coherent structure, with a f…
The Fall and Rise of V854 Centauri: Long-Term Ultraviolet Spectroscopy of a Highly Active R Coronae Borealis Star
Marang, Fred; Clayton, Geoffrey C.; Lawson, Warrick A. +6 more
We examine long-term low-dispersion International Ultraviolet Explorer SWP and LWP spectroscopy of the R Coronae Borealis (RCB) star V854 Cen, obtained across the deep (DeltaV>6 mag) 1991, 1992-1993, and 1994 declines. We also report the optical light curve for the star in the interval 1987-1998, including multicolor photometry obtained during …
Multiresolution wavelet analysis of SUMER/SOHO observations in a solar prominence
Vial, J. -C.; Bocchialini, K.; Rovira, M. +3 more
We have studied through a multiresolution wavelet analysis the oscillations in a limb prominence. Intensity fluctuations in time and height corresponding to different lines of Si iv and O iv observed with SUMER on board SOHO have been analyzed in the wavelet bands of J3= 1 min 36 s to 3 min 12 s and J4=3 min 12 s to 6 min 24 …
The Central Regions of M81
Davidge, T. J.; Courteau, S.
High-angular resolution near-infrared images obtained with the Canada-France-Hawaii Telescope adaptive optics system are combined with archival Hubble Space Telescope data to investigate the central regions of the nearby Sb galaxy M81 (NGC 3031). The spectral-energy distribution of the circumnuclear region, which extends out to 1.5" (~24 pc if mu_…
Identification of absorbing galaxies towards the QSO J2233-606 in the Hubble Deep Field South
Tresse, Laurence; Petitjean, Patrick; Cristiani, Stefano +2 more
We present spectroscopic observations of galaxies lying within 1' of QSO J2233-606 in the Hubble Deep Field South (HDF-S). Several are found to be coincident in redshift with absorption-line systems seen in the HST J2233-606 spectrum. We detect a new z_em = 1.336 QSO with I = 20.8 at a projected angular separation of 44.5'' (or rho = 200h(-1) kpc;…
Power spectra comparison between GOLF and spatially masked MDI velocity signals
Henney, C. J.; Scherrer, P. H.; Turck-Chièze, S. +5 more
The Global Oscillations at Low Frequency (GOLF) and the Michelson Doppler Imager (MDI) instruments aboard the Solar and Heliospheric Observatory (SOHO) give an excellent opportunity to search for solar low frequency oscillation modes previously undetected from ground based experiments. Presented here is a comparison of the velocity power spectra b…
Fate of the Universe, Age of the Universe, Dark Matter, and the Decaying Vacuum Energy
Özer, Murat
It is shown that in cosmological models based on a vacuum energy decaying as a-2, where a is the scale factor of the universe, the fate of the universe in regard to whether it will collapse in the future or expand forever is determined not by the curvature constant k but by an effective curvature constant keff. It is argued t…
Ionized ultraviolet and soft X-ray absorption in the low-redshift active galactic nucleus PG 1126-041
Wamsteker, W.; Brinkmann, W.; Wang, J. X. +2 more
We present here the analysis of ultraviolet spectra from IUE and an X-ray spectrum from ROSAT PSPC observations of the X-ray-weak, far-infrared-loud AGN, PG 1126-041 (Mrk 1298). The first UV spectra taken in 1992 June, simultaneously with ROSAT, show strong absorption lines of Nv, Civ and Siiv, extending over a velocity range from -1000 to -5000km…