Search Publications
The dispersion in the Cepheid period-luminosity relation and the consequences for the extragalactic distance scale
Shanks, Tom; Allen, Paul D.
Using published Hubble Space Telescope (HST) Cepheid data from 25 galaxies, we have found a correlation between the dispersion in the Cepheid period-luminosity (P-L) relation and host galaxy metallicity, which is significant at the ~3σ level in the V band. In the I band the correlation is less significant, although the tighter intrinsic dispersion…
Cassini/VIMS observation of an Io post-eclipse brightening event
Brown, R. H.; Baines, K. H.; Buratti, B. J. +10 more
During the Cassini-Jupiter flyby, VIMS observed Io at different phase angles, both in full sunlight and in eclipse. By using the sunlight measurements, we were able to produce phase curves in the visual through all the near infrared wavelengths covered by the VIMS instrument (0.85-5.1 µm). The phase angle spanned from ∼2° to ∼120°. The measu…
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…
Global control of merging by the interplanetary magnetic field: Cluster observations of dawnside flank magnetopause reconnection
Balogh, A.; RèMe, H.; André, M. +7 more
Detailed Cluster observations of flank magnetopause reconnection are presented for two events on the Northern and the Southern Hemispheric dawnside flanks when the interplanetary magnetic field (IMF) clock angle ? = arctan(By/Bz) is within ∼45° of the equatorial plane. The event selection is based on the relative proximity be…
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…
A serendipitous survey for galaxy clusters by the XMM-Newton Survey Science Center
Elvis, M.; Watson, M. G.; Lamer, G. +6 more
We describe the initial results of a programme to detect and identify extended X-ray sources found serendipitously in XMM-Newton observations. We have analyzed 186 EPIC-PN images at high galactic latitude with a limiting flux of 1 × 10 -14 erg cm -2 s -1 and found 62 cluster candidates. Thanks to the enhanced sensi…
Mid-infrared imaging and modelling of the dust shell around post-AGB star HD 187885 (IRAS 19500-1709)
Gledhill, T. M.; Clube, K. L.
We present 10- and 20-µm images of IRAS 19500-1709 taken with the mid-infrared camera, OSCIR, mounted on the Gemini North Telescope. An extended circumstellar envelope is detected, with the N-band image indicating an elongation in a north-east-south-west direction. We use a dust radiation transport code to fit the spectral energy distributio…
A New Way to Model the Solar Oscillation ℓ−ν Power Spectrum
Jefferies, Stuart M.; Vorontsov, Sergei V.
We present a new approach for the precise and accurate forward modeling of the solar oscillation ℓ−ν power spectrum. The approach is designed to provide the basis for a streamlined solar seismic inversion without measurements of the p-mode frequencies. The new strategy represents a paradigm change in how information is extracted from the oscillati…
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…
The composite starburst/AGN nature of the superwind galaxy NGC 4666
Palazzi, E.; Cappi, M.; Franceschini, A. +6 more
We report the discovery of a Compton-thick AGN and of intense star-formation activity in the nucleus and disk, respectively, of the nearly edge-on superwind galaxy NGC 4666. Spatially unresolved emission is detected by BeppoSAX only at energies <10 keV, whereas spatially resolved emission from the whole disk is detected by XMM-Newton. A promine…