Search Publications
Models for Solar Magnetic Loops. IV. On the Relation between Coronal and Footpoint Plasma in Active Region Loops
Landi, E.; Feldman, U.
In the present work we analyze several SUMER intensity maps of active region solar loops in order to compare the relative brightnesses of the footpoints and the coronal section of active region loops. We find that the former are barely distinguishable from the background emission of the active region, while the coronal emission of loops is confine…
Two New X-Ray/Optical/Radio Supernova Remnants in M31
Gelfand, Joseph D.; Williams, Benjamin F.; Kong, Albert K. H. +3 more
We compare a deep (37 ks) Chandra ACIS-S image of the M31 bulge to Local Group Survey narrowband optical data and Very Large Array (VLA) radio data of the same region. Our precisely registered images reveal two new optical shells with X-ray counterparts. These shells have sizes, [SII]/Hα flux ratios, and X-ray spectral properties typical of supern…
Warm-hot Intergalactic Medium Emission and the Cluster Soft Excess: A Model Comparison
Bonamente, M.; Mittaz, J.; Lieu, R. +1 more
The confirmation of the cluster soft excess (CSE) by XMM-Newton has rekindled interest as to its origin. The recent detections of CSE emission at large cluster radii together with reports of O VII line emission associated with the CSE has led many authors to conjecture that the CSE is, in fact, a signature of the warm-hot intergalactic medium (WHI…
Proper Motion Objects in the Hubble Deep Field
Winget, D. E.; von Hippel, Ted; Mendez, R. A. +1 more
Using the deepest and finest resolution images of the universe acquired with the Hubble Space Telescope and a similar image taken 7 yr later for the Great Observatories Origins Deep Survey, we have derived proper motions for the point sources in the Hubble Deep Field-North. Two faint blue objects, HDF 2234 and HDF 3072, are found to display signif…
Advanced Camera for Surveys Observations of a Strongly Lensed Arc in a Field Elliptical Galaxy
Ford, H. C.; Infante, L.; Zheng, W. +15 more
We report the discovery of a strongly lensed arc system around a field elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images of a parallel field observed during NICMOS observations of the HST Ultra Deep Field. The ACS parallel data comprise deep imaging in the F435W, F606W, F775W, and F850LP bandpasses. The mai…
Atomic Data and Spectral Line Intensities for Ca VIII
Landi, E.; Storey, P. J.; Zeippen, C. J.
In the present work a complete set of energy levels, spontaneous radiative decay rates, and thermally averaged collision strengths are calculated for the first time for the five lowest electron configurations of Ca VIII, corresponding to 40 fine-structure energy levels. Collision data are calculated using the R-matrix approximation, and results ar…
Multivariate Monte Carlo Methods for the Reflection Grating Spectrometers on XMM-Newton
Kahn, S. M.; Peterson, J. R.; Jernigan, J. G.
We propose a novel multivariate Monte Carlo method as an efficient and flexible approach to analyzing extended X-ray sources with the reflection grating spectrometers (RGS) on XMM-Newton. A multidimensional interpolation method is used to efficiently calculate the response function for the RGS in conjunction with an arbitrary spatially varying spe…
FUSE Observations of Highly Ionized Gas in the Vela Supernova Remnant
Blair, William P.; Nichols, Joy S.; Slavin, Jonathan D.
We present Far Ultraviolet Spectroscopic Explorer (FUSE) data on O VI absorption lines observed toward nine stars behind the Vela supernova remnant (SNR). The O VI observations are compared with International Ultraviolet Explorer (IUE) observations of C IV absorption toward the same stars. All of these stars are B stars, which generally have compl…
Evidence for the Same Hot Plasma after Coronal Mass Ejection Events, in Both Remote and In Situ Observations
Poletto, G.; Ko, Y. -K.; Bemporad, Alessandro +4 more
We present here evidence for highly ionized Fe observed both in the corona, in the aftermath of a coronal mass ejection, and, after propagation, in situ. The apparent source temperature is greater than 6 MK. To our knowledge, this is the first time that such an unambiguous identification has been made. This detection complements studies correlatin…
The Nature of Close Companions of the BL Lacertae Objects 1ES 0502+675 and 1ES 1440+122
Falomo, R.; Treves, A.; Urry, C. M. +2 more
We report on deep radio images and optical spectroscopy of two BL Lac objects that have very close compact companions. The two targets, 1ES 0502+675 and 1ES 1440+122, were selected from the Hubble Space Telescope imaging survey of 110 BL Lacs as candidates for possible gravitational lensing. The new observations clearly demonstrate that the compan…