Search Publications
Characteristic Scales of Chromospheric Oscillation Wave Packets
McIntosh, Scott W.; Smillie, Darren G.
We use wavelet transforms to study the characteristic time scales of chromospheric oscillation ``wave packets'' that are observed in Transition Region and Coronal Explorer (TRACE) ultraviolet continuum image time series. Using several data sets, we investigate the statistical, spatial, and temporal intermittence of the number, duration, mean frequ…
An X-Ray Investigation of the NGC 346 Field in the Small Magellanic Cloud. III. XMM-Newton Data
Corcoran, Michael F.; Stevens, Ian R.; Nazé, Yaël +2 more
We present new XMM-Newton results on the field around the NGC 346 star cluster in the SMC. This continues and extends previously published work on Chandra observations of the same field. The two XMM-Newton observations were obtained, respectively, 6 months before and 6 months after the previously published Chandra data. Of the 51 X-ray sources det…
XMM-Newton Observation of the Double Pulsar System J0737-3039
Campana, Sergio; Possenti, Andrea; Burgay, Marta
We report on a 50 ks XMM-Newton observation of the double pulsar system J0737-3039 performed in 2004 April. We present results of the spectral analysis of these data combined with the much shorter Chandra pointing performed in 2004 January. Blackbody emission with an effective temperature of 0.20+0.02-0.02 keV (90% confidence…
A Detailed Study of Opacity in the Upper Atmosphere of Proxima Centauri
Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S. +2 more
We present far-UV and UV spectroscopic observations of Proxima Centauri obtained as part of our continued investigation into the optically thin approximation assumed for the transition regions of late-type stars. Significant opacity is found in the C III lines during both the quiescent and flaring states of Proxima Cen, with up to 70% of the expec…
Observations of Water Vapor Outflow from NML Cygnus
Li, Di; Lim, Tanya; Feuchtgruber, Helmut +2 more
We report new observations of the far-infrared and submillimeter water vapor emission of NML Cygnus based on data gathered with the Infrared Space Observatory and the Submillimeter Wave Astronomy Satellite. We compare the emission from NML Cyg to that previously published for VY CMa and W Hya in an attempt to establish the validity of recently pro…
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…
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…