Search Publications
VLF wave activity in the solar wind and the photoelectron effect in electric field measurements: Ulysses observations
Balogh, A.; McComas, D. J.; Lin, Naiguo +2 more
We present observations of very low frequency (VLF) waves (0.2 to 448 Hz) made by Ulysses during the solar maximum and compare the observations with those obtained when the solar activity was approaching a minimum. The occurrences and properties of the waves are found to be similar during the solar maximum and solar minimum periods for slow and in…
The RCW 114 nebula: An old supernova remnant or a WR wind-blown bubble?
Lallement, R.; Welsh, B. Y.; Sallmen, S. +1 more
We present medium resolution spectra (R ~ 7 km s-1) of the interstellar NaI D1 & D2 absorption lines observed towards 7 early-type stars with distances ranging from 221 to ~ 1.5 kpc in the line-of-sight to the RCW 114 nebula. Our observed pattern of absorption is in conflict with the findings of Bedford et al. (1984) who placed an u…
Probing the extended emission-line region in 3C 171 with high-frequency radio polarimetry
Hardcastle, M. J.
I present high-frequency polarimetric radio observations of the radio galaxy 3C 171, in which depolarization is associated with an extended emission-line region. The radio hotspots, known to be depolarized at low radio frequencies, become significantly polarized above (observer's frame) frequencies of 15 GHz. There is some evidence that some of th…
The Nature of the Ultraviolet/X-Ray Absorber in PG 2302+029
Hamann, Fred; Shields, Joseph C.; Jannuzi, Buell T. +2 more
We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029. This quasar has a rare system of ultra-high-velocity (-56,000 km s-1) UV absorption lines that form in an outflow from the active nucleus. The Chandra data indicate that soft X-ray absorption is also present. We perform a joint UV and X-ray analysis, using photoio…
Technique for Detecting Warm-Hot Intergalactic Gas in Quasar Ultraviolet Spectra
Binette, Luc; Rodríguez-Martínez, Mario; Haro-Corzo, Sinhue +1 more
The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~1200 Å. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being intrinsic to quasars. We consider the possibility that the steepening may result from a tenuous absorption compone…
Flare characteristics: Properties of eruptive and non-eruptive events and their associations
Culhane, J. L.; Harra, L. K.; Kay, H. R. M. +1 more
The complex: relationship between solar flares and coronal mass ejections is investigated using a comparison of flare parameters for a total of 69 ejective and non-ejective flares. In the case of solar flares which do not show mass ejection there seems to be a clear relationship between the peak intensity and duration, with higher intensity events…
The Hubble Deep Field South Flanking Fields
Ferguson, Henry C.; Lucas, Ray A.; Baum, Stefi A. +22 more
As part of the Hubble Deep Field South program, a set of shorter two-orbit observations were obtained of the area adjacent to the deep fields. The WFPC2 flanking fields cover a contiguous solid angle of 48 arcmin2. Parallel observations with the STIS and NICMOS instruments produce a patchwork of additional fields with optical and near-i…
First INTEGRAL observations of eight persistent neutron star low mass X-ray binaries
Frontera, F.; Goldoni, P.; Santangelo, A. +16 more
Early results from the INTEGRAL Core Program, for a sample of eight persistently bright neutron star low mass X-ray binaries in the energy range from 5 keV to 200 keV, are presented. It is shown that INTEGRAL efficiently detects sources and that spectra may be obtained up to several hundreds of keV by combining data from three of the four INTEGRAL…
LBQS 1429-0053: A binary quasar rather than a lensed quasar.
Kneib, J. -P.; Faure, C.; Alloin, D. +3 more
Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a binary quasar or a doubly-imaged lensed quasar. Direct search of a putative lensing galaxy is unsuccessful down to R=27, J=24, Ks=22.5 and H=22.5. Moreover, no galaxy overdensity close to the quasar…
Comparison of Total Solar Irradiance with NASA/National Solar Observatory Spectromagnetograph Data in Solar Cycles 22 and 23
Jones, Patricia B.; Jones, Harrison P.; Branston, Detrick D. +1 more
NASA/National Solar Observatory Spectromagnetograph (SPM) data are compared with spacecraft measurements of total solar irradiance (TSI) variations for 8 yr beginning with the declining phase of solar cycle 22 and extending into the maximum of cycle 23. Previously reported conclusions based on a similar comparison for a shorter time period appear …