Search Publications
Physical Structure of Planetary Nebulae. III. The Large and Evolved NGC 1360
Guerrero, Martín A.; Chu, You-Hua; Gruendl, Robert A. +1 more
NGC 1360 is a large planetary nebula (PN) without an obvious shell morphology. We have analyzed Hα images and high-dispersion echelle spectra of NGC 1360 in order to construct spatio-kinematic models and to determine its density distribution. The best-fit model indicates that NGC 1360 is a prolate ellipsoidal shell whose major axis is twice as lon…
Cosmic Filaments in Superclusters
Miller, Eric D.; Bregman, Joel N.; Dupke, Renato A.
Large-scale structure calculations show that modest overdensity filaments will connect clusters of galaxies and these filaments are reservoirs of baryons, mainly in gaseous form. To determine whether such filaments exist, we have examined the UV absorption line properties of three active galactic nuclei (AGNs) projected behind possible filaments i…
The Effects of Periodically Gapped Time Series on Cross-Correlation Lag Determinations
Maraschi, L.; Treves, A.; Celotti, A. +2 more
The three bright TeV blazars Mrk 421, Mrk 501, and PKS 2155-304 are highly variable in synchrotron X-ray emission. In particular, these sources can exhibit variable time lags between flux variations at different X-ray energy bands. However, there are a number of issues that may significantly bias lag determinations. Edelson et al. (2001) recently …
Optical and IUE Spectra of the Planetary Nebula NGC 7026
Feibelman, Walter A.; Hyung, Siek
We investigated spectroscopic data of the extended planetary nebula NGC 7026 in the wavelengths 3700-10,050 Å, secured with the Hamilton Echelle Spectrograph at Lick Observatory. This optical wavelength spectrum has been analyzed along with the International Ultraviolet Explorer (IUE) UV spectral data. The diagnostic diagram indicates that the pla…
Detection of Atomic Chlorine in Io's Atmosphere with the Hubble Space Telescope GHRS
Feldman, Paul D.; Strobel, Darrell F.; McGrath, Melissa A. +1 more
We report the detection of atomic chlorine emissions in the atmosphere of Io using Hubble Space Telescope observations with the Goddard High Resolution Spectrograph (GHRS). The Cl I λ1349 dipole allowed and Cl I] λ1386 forbidden transition multiplets are detected at a signal-to-noise ratio of 6 and 10, respectively, in a combined GHRS spectrum acq…
Far-Ultraviolet Observations of RR Lyrae Stars in the Core of NGC 1851
Anderson, Scott F.; Homer, Lee; Margon, Bruce +1 more
There are extraordinarily few far-ultraviolet (FUV) observations of RR Lyrae stars in the literature. We present Hubble Space Telescope (HST) FUV (~1600 Å) imaging of the core of the globular cluster NGC 1851. Eleven new variables with light curves consistent with those of RR Lyrae stars are discovered, increasing the total number of RR Lyrae know…
Modelling of dust scattering toward the Coalsack
Shalima, P.; Murthy, Jayant
Murthy, Henry & Holberg discovered intense far-ultraviolet (FUV) (λλ912-1600) emission from the direction of the Coalsack molecular cloud 10 years ago. We have used their results in conjunction with a Monte Carlo model for the scattering in the region to show that the scattering is from dust in the foreground of the Coalsack. The albedo of the…
The Zeeman-sensitive Emission Lines of Mg I at 12 Microns in Procyon
Ryde, N.; Ryde, F.; Korn, A. J. +1 more
Emission lines of magnesium at 12 µm have been observed in the spectrum of Procyon. We reproduce the observed disk-averaged line flux from Procyon (as well as the observed intensity profiles from the Sun) by calculating the line formation and relaxing the assumption of local thermodynamic equilibrium. We find that the lines in Procyon are fo…
Analysis of a Solar Eruptive Event on November 4, 2001, Using CORONAS-F/SPIRIT Data
Grechnev, V. V.; Chertok, I. M.; Kuzin, S. V. +5 more
We analyze large-scale solar activity following the eruption of a very powerful, geoeffective coronal mass ejection in the 23rd solar cycle, observed at 175, 284, and 304 Å on November 4, 2001, using data from the CORONAS-F/SPIRIT telescope. In particular, we have shown that the restructuring of the magnetic field above the eruption center was acc…
Continuous and burst-like accretion on to substellar companions in Mira winds
Struck, Curtis; Cohanim, Babak E.; Willson, Lee Anne
We present numerical hydrodynamical modelling of the effects of a giant planet or brown-dwarf companion orbiting within the extended atmosphere and wind formation zone of an approximately solar-mass Mira variable star. The large-scale, time-dependent accretion flows within the radially oscillating and outflowing circumstellar gas around Miras are …