Search Publications
The correlation between solar energetic particle peak intensities and speeds of coronal mass ejections: Effects of ambient particle intensities and energy spectra
Kahler, S. W.
The correlation of peak intensities of solar energetic particle (SEP) events with the speeds of the associated coronal mass ejections (CMEs) is understood to be a result of SEP acceleration at shocks driven by the CMEs. However, the peak SEP intensities associated with CMEs of a given speed vary over ~ 4 orders of magnitude. We examine a database …
Observational Determination of the Rate of Magnetic Helicity Transport through the Solar Surface via the Horizontal Motion of Field Line Footpoints
Chae, Jongchul
Magnetic helicity may be transported to the solar corona through the solar surface either via the passage of helical magnetic field lines from below or via the shuffling of footpoints of preexisting coronal field lines. In this Letter, we show how to observationally determine the rate of magnetic helicity transport via photospheric footpoint shuff…
High-Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
Heinke, Craig; Murray, Stephen S.; Edmonds, Peter D. +1 more
We have obtained high-resolution (<~1'') deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (Lx ~ 1030-33 e…
EXPORT: Spectral classification and projected rotational velocities of Vega-type and pre-main sequence stars
Rauer, H.; Schneider, J.; Eiroa, C. +19 more
In this paper we present the first comprehensive results extracted from the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary Observational Research Team) consortium. During 1998-1999, EXPORT carried out an intensive observational effort in the framework of the origin and evolution of protoplanetary systems in order to obtain clues o…
delta Scuti and related stars: Analysis of the R00 Catalogue
Rodríguez, E.; Breger, M.
We present a comprehensive analysis of the properties of the pulsating delta Scuti and related variables based mainly on the content of the recently published catalogue by Rodríguez et al. (\cite{retal00a}, hereafter R00). In particular, the primary observational properties such as visual amplitude, period and visual magnitude and the contribution…
Chandra Observations of ``The Antennae'' Galaxies (NGC 4038/9)
Zezas, A.; Fabbiano, G.; Murray, S. S.
We report the results of a deep Chandra ACIS pointing at the merging system NGC 4038/9. We detect an extraordinarily luminous population of X-ray sources, with luminosity well above that of XRBs in M31 and the Milky Way. If these sources are unbeamed XRBs, our observations may point to them being 10-(a few)100 Msolar black hole counterp…
Population Gradients in Local Group Dwarf Spheroidal Galaxies
Grebel, Eva K.; Dolphin, Andrew; Holtzman, Jon +7 more
We present a systematic and homogeneous analysis of population gradients for the Local Group dwarf spheroidal galaxies (dSph's) Carina, Sculptor, Sextans, Tucana, and Andromeda I-III, V, and VI. For all of the Milky Way companions studied here, we find significant population gradients. The same is true for the remote dSph Tucana located at the out…
Investigation of Mass Flows beneath a Sunspot by Time-Distance Helioseismology
Zhao, Junwei; Kosovichev, Alexander G.; Duvall, Thomas L., Jr.
A time-distance helioseismic technique is employed to analyze a set of high-resolution Dopplergram observations of a large sunspot by SOHO/MDI on 1998 June 18. A regularized, damped least-squares inversion is applied to the measurements of travel times to infer mass flows around the sunspot below the solar surface. Powerful converging and downward…
XMM-Newton observations of the cluster of galaxies Sérsic 159-03
Kaastra, J. S.; Ferrigno, C.; Tamura, T. +3 more
The cluster of galaxies Sérsic 159-03 was observed with the XMM-Newton X-ray observatory as part of the Guaranteed Time program. X-ray spectra taken with the EPIC and RGS instruments show no evidence for the strong cooling flow derived from previous X-ray observations. There is a significant lack of cool gas below 1.5 keV as compared to standard i…
Nuclear Luminosities and Radio Loudness of Seyfert Nuclei
Ho, Luis C.; Peng, Chien Y.
Historically, Seyfert nuclei have been considered to be radio-quiet active galactic nuclei (AGNs). We question this widely held assumption by showing that the distribution of the radio-to-optical luminosity ratio, R≡Lν(6 cm)/Lν(B), when properly measured for the nuclear component, places the majority of type 1 Seyfert nuclei …