Search Publications
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…
Deviations from the Flux-Recurrence Time Relationship in GS 1826-238: Potential Transient Spectral Changes
Rothschild, Richard E.; Galloway, Duncan K.; Homer, Lee +1 more
The low-mass X-ray binary GS 1826-238 is presently unique for its consistently regular bursting behavior. In previous Rossi X-Ray Timing Explorer (RXTE) measurements between 1997 November and 2002 July, this source exhibited (nearly) limit-cycle bursts with recurrence times that decreased proportionately as the persistent flux increased. Here we r…
Non-Local Thermodynamic Equilibrium Model of NGC 6543's Central Star and Its Relation to the Surrounding Planetary Nebula
Hillier, D. J.; Richer, M. G.; Peimbert, M. +3 more
We analyze the chemical composition of the central star of the planetary nebula NGC 6543 based on a detailed NLTE model of its stellar wind. The logarithmic abundances by number are H = 12.00, He = 11.00, C = 9.03, N = 8.36, O = 9.02, Si = 8.19, P = 5.53, S = 7.57, and Fe = 7.24. Compared with the solar abundances, most of the elements have solar …
XMM-Newton Discovery of 217 s Pulsations in the Brightest Persistent Supersoft X-Ray Source in M31
Trudolyubov, Sergey P.; Priedhorsky, William C.
We report on the discovery of a periodic modulation in the bright supersoft X-ray source XMMU J004252.5+411540 detected in the 2000-2004 XMM-Newton observations of M31. The source exhibits X-ray pulsations with a period P ~ 217.7 s and a quasi-sinusoidal pulse shape and pulsed fraction ~7%-11%. We did not detect statistically significant changes i…
Intergalactic He II Absorption in the Spectra of Quasars at Redshifts 3.5 and 3.8, Observed with the HST ACS Prism
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +8 more
We present the UV spectra of two quasars obtained with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) prism (R ~ 100). One quasar, at redshift z = 3.5, shows an absorption edge consistent either with nearly fully ionized helium with an intergalactic He II Lyα optical depth at 304 Å of τ304 > 3.1 (90% confidence), or…