Search Publications
How Do f-Mode Frequencies Change with Solar Radius?
Antia, H. M.; Chatterjee, Piyali
We test the relation between relative f-mode frequency variation (δ ν/ν) and Lagrangian perturbation in the solar radius (δ r/r) obtained by Dziembowski and Goode using several pairs of solar models and show that it does not hold true for any of the model pairs we have used. We attempt to derive a better approximation for the kernel linking the re…
The FR II Broad-Line Seyfert 1 Galaxy: PKS J1037-2705
Clarke, Tracy E.; Punsly, Brian; Tingay, Steven +3 more
In this article we demonstrate that PKS J1037-2705 has a weak accretion flow luminosity, well below the Seyfert 1/QSO dividing line, weak broad emission lines (BELs), and moderately powerful FR II extended radio emission. It is one of the few documented examples of a broad-line object in which the time-averaged jet kinetic luminosity, \overline{Q}…
Constraints on the Velocity and Spatial Distribution of Helium-like Ions in the Wind of SMC X-1 from Observations with the XMM-Newton Reflection Grating Spectrometer
Kallman, Timothy R.; Liedahl, Duane A.; Wojdowski, Patrick S.
We present here X-ray spectra of the HMXB SMC X-1 obtained in an observation with the XMM-Newton observatory beginning before eclipse and ending near the end of eclipse. With RGS on board XMM-Newton, we observe emission lines from hydrogen-like and helium-like ions of nitrogen, oxygen, neon, magnesium, and silicon. Although the resolution of the R…
Is the Optically Unidentified Radio Source FIRST J121839.7+295325 a Dark Lens?
Keeton, C. R.; Ryan, R. E., Jr.; Windhorst, R. A. +2 more
We present evidence that the optically unidentified radio source FIRST J121839.7+295325 may be strongly lensing a background galaxy. We estimate the redshift of the assumed gravitational arc, discovered in parallel imaging with HST, from MMT-Blue Channel spectroscopy to be zarc = 2.48-0.05+0.14. We present lens mod…
Effects of Solar Magnetic Activity on the Charge States of Minor Ions of Solar Wind
Wurz, Peter; Klecker, Berndt; Wang, Xuyu
We present an investigation of the effects of solar magnetic activity on the charge states of minor ions (Fe, Si, Mg, Ne, O, C) in the solar wind using ACE solar wind data, the "current sheet source surface" (CSSS) model of the corona, and SOHO MDI data during the 23rd solar cycle. We find that the mean charge states indicate a clear trend of incr…
Radio Continuum Observations of the Candidate Supermassive Black Hole in the Dwarf Elliptical VCC 128
Pasquali, Anna; Seth, Anil; Debattista, Victor P. +4 more
The presence of black holes (BHs) at the centers of dwarf elliptical galaxies (dEs) has been argued both theoretically and observationally. Using archival HST WFPC2 data, we found the Virgo cluster dwarf elliptical galaxy VCC 128 to harbor a binary nucleus, a feature that is usually interpreted as the observable signature of a stellar disk orbitin…
Time-Resolved FUSE Spectroscopy of the LMC WC + O Binaries Br 22 and Br 32
Moffat, Anthony F. J.; St-Louis, Nicole; Marchenko, Sergey V. +1 more
Using the Far Ultraviolet Spectroscopic Explorer satellite, we obtained series of spectra for two of the three known WC + O binaries in the LMC, Br 22, and Br 32 (HD 36521). Compared to Br 22, we detect a higher ratio of C IV to He II lines in Br 32, which could indicate a more advanced evolutionary stage for the latter. The orbit of the O star in…
Ice Emission and the Redshifts of Submillimeter Sources
Maloney, P. R.; Imanishi, M.; Dudley, C. C.
Observations at submillimeter wavelengths have revealed a population of sources thought to be at relatively large redshifts. The position of the 850 µm passband on the Rayleigh-Jeans portion of the Planck function leads to a maximum redshift estimate of z ~ 4.5, since sources will not retain their redshift-independent brightness close to the…
Erratum: "Probing Elemental Abundances in SNR 1987A using XMM-Newton" (ApJ, 676, 361 [2008])
Haberl, Frank; Heng, Kevin; Hasinger, Günther +1 more
Could We Have Forecast "The Day the Solar Wind Died"?
McIntosh, Scott W.; Leamon, Robert J.
In 1999 May an interval of unusually slow (<300 km s-1) and rarefied (<1 cm-3) solar wind was observed upstream of Earth by the ACE spacecraft. The event has been dubbed "The Day the Solar Wind Died." We apply our solar wind forecast model to the interval in question, to ask whether we could have predicted the phenomeno…