Search Publications
The dwarf galaxy population in Abell 2218
Driver, Simon P.; De Propris, Roberto; Nulsen, Paul E. J. +2 more
We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z= 0.18) based on archival Hubble Space Telescope WFPC2 F606W images. These have been used to derive the luminosity function to extremely faint limits (MF606W~-13.2 mag, µ0~ 24.7 mag arcsec-2) over a wide field of view (1.…
Constraining the very heavy elemental abundance peak in the chemically peculiar star χ Lupi, with new atomic data for Os II and Ir II
Leckrone, D. S.; Lundberg, H.; Wahlgren, G. M. +2 more
The determination of elemental abundances plays an important role in understanding the atmospheric processes that lead to anomalies in spectra of chemically peculiar stars. Ongoing study of the HgMn star χ Lupi has defined much of the elemental abundance distribution but progress is dependent upon the availability and accuracy of the atomic data. …
Phase Variation in the Pulse Profile of SMC X-1
Neilsen, J.; Hickox, R. C.; Vrtilek, S. D.
We present the results of the timing and spectral analysis of X-ray high-state observations of the high-mass X-ray pulsar SMC X-1 with Chandra, XMM-Newton, and ROSAT, taken between 1991 and 2001. The source has LX~(3-5)×1038 ergs s-1, and the spectra can be modeled as a power law plus blackbody with kTBB…
Mid-infrared selection of AGN
Siebenmorgen, R.; Schartel, N.; Haas, M. +6 more
Since a large fraction of active galactic nuclei (AGN) is missed in common UV-excess surveys and is even hard to find in radio, near-IR and X-ray surveys, we have used a new AGN selection technique which is expected to be not affected by extinction. Within the scientific verification of the ISOCAM Parallel Survey at 6.7 µm we have discovered…
A spectral and spatial analysis of η Carinae's diffuse X-ray emission using CHANDRA
Weis, K.; Bomans, D. J.; Davidson, K. +1 more
The luminous unstable star (star system) η Carinae is surrounded by an optically bright bipolar nebula, the Homunculus and a fainter but much larger nebula, the so-called outer ejecta. As images from the EINSTEIN and ROSAT satellites have shown, the outer ejecta is also visible in soft X-rays, while the central source is present in the harder X-ra…
Derivation of electric potential patterns in the inner magnetosphere from Cluster EDI data: Initial results
Torbert, R. B.; Matsui, H.; Quinn, J. M. +2 more
Electric potential patterns are derived in the inner magnetosphere at 4 < L < 10 using 2 years of data from the Electron Drift Instrument (EDI) on Cluster. First, we examine the relations between the electric field and the following three parameters to understand how the potential patterns are organized: BZ component of the interp…
Densities and Velocities in Fast Coronal Mass Ejections: Radiative Pumping of the O VI Doublet
Raymond, J. C.; Ciaravella, A.
In very fast coronal mass ejections (CMEs), it is possible for O VI ions to scatter Lyβ photons that originate in the solar chromosphere and for the λ1037 transition of O VI to scatter λ1032 photons from the solar transition region. This scattering process can be identified by departures of the O VI I1032/I1037 intensity rati…
Very High Iron Abundance of the Hot Gas around the cD Galaxy of the MKW 4 Cluster
Fukazawa, Yasushi; Kawano, Naomi; Kawashima, Kengo
We observed a nearby X-ray-bright poor cluster MKW 4 with Chandra. The iron abundance is found to increase dramatically from 0.3 to 1.3 solar within 150" of the cD galaxy NGC 4073. Then MKW 4 is the second cluster to exhibit a significantly high metallicity of greater than 1 solar, after the Centaurus Cluster. Weakness of the central cool componen…
A View of PKS 2155-304 with XMM-Newton Reflection Grating Spectrometers
Maraschi, L.; Tavecchio, F.; Treves, A. +2 more
We present the high-resolution X-ray spectrum of the BL Lac object PKS 2155-304 taken with the RGS units on board XMM-Newton in 2000 November. We detect an O VII Kα resonant absorption line from warm/hot local gas at 21.59 Å (~4.5 σ detection). The line profile is possibly double peaked. We do not confirm the strong 20.02 Å absorption line seen wi…
Pickup ions at Dione and Enceladus: Cassini Plasma Spectrometer simulations
Crary, F.; Johnson, R. E.; Young, D. T. +5 more
Voyager images of the icy satellites of Saturn, Dione and Enceladus, suggest that they may have been geologically active and are not only composed of ice. Recent observations by the Hubble Space Telescope have shown the presence of ozone at both Dione and Rhea, which also implies the presence of molecular oxygen at these bodies. Observations of Ar…