Search Publications
Ionized nebulae surrounding brightest cluster galaxies
Fabian, A. C.; Crawford, C. S.; Hatch, N. A.
We present integral field spectroscopic observations of six emission-line nebulae that surround the central galaxy of cool core clusters. Qualitatively similar nebulae are observed in cool core clusters even when the dynamics and possibly formation and excitation source are different. Evidence for a nearby secondary galaxy disturbing a nebula, as …
An absorption origin for the soft excess in Seyfert 1 active galactic nuclei
Done, Chris; Gierliński, Marek; Middleton, Matthew
The soft excess seen in the X-ray spectra of many active galactic nuclei (AGN) can be well modelled by reflection from a partially ionized accretion disc. However, this often requires extreme parameters, both in terms of the underlying space-time and the reflection geometry, and requires that the disc is far from hydrostatic equilibrium. An altern…
The composition of Saturn's E ring
Kempf, S.; Postberg, F.; Srama, R. +7 more
We present the first in situ direct measurement of the composition of particles in Saturn's rings. The Cassini cosmic dust analyser (CDA) measured the mass spectra of nearly 300 impacting dust particles during the 2004 October E ring crossing. An initial interpretation of the data shows that the particles are predominantly water ice, with minor co…
Testing the accuracy of synthetic stellar libraries
Coelho, Paula; Martins, Lucimara P.
One of the main ingredients of stellar population synthesis models is a library of stellar spectra. Both empirical and theoretical libraries are used for this purpose, and the question about which one is preferable is still debated in the literature. Empirical and theoretical libraries are being improved significantly over the years, and many libr…
A deeper search for the progenitor of the Type Ic supernova 2002ap
Smartt, S. J.; Young, D. R.; Maund, J. R. +6 more
Images of the site of the Type Ic supernova (SN) 2002ap taken before explosion were analysed previously by Smartt et al. We have uncovered new unpublished, archival pre-explosion images from the Canada-France-Hawaii Telescope (CFHT) that are vastly superior in depth and image quality. In this paper we present a further search for the progenitor st…
The XMM-Large Scale Structure catalogue: X-ray sources and associated optical data. Version I
Maccagni, D.; Chiappetti, L.; Altieri, B. +34 more
Following the presentation of the XMM-Large Scale Structure (XMM-LSS) survey X-ray source detection package by Pacaud et al., we provide the source lists for the first surveyed 5.5deg2. The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 point-like or extended sources above a detection likelihood of 15 i…
A limit on the presence of Earth-mass planets around a Sun-like star
Steffen, Jason H.; Agol, Eric
We present a combined analysis of all publicly available visible Hubble Space Telescope observations of transits of the planet HD 209458b. We derive the times of transit, planet radius, inclination, period, and ephemeris. We then use the times of transit to place constraints on the existence of secondary planets in the system. We show that planets…
Bulk Comptonization spectra in blazars
Ghisellini, G.; Fabian, A. C.; Celotti, A.
We study the time-dependent spectra produced via the bulk Compton process by a cold, relativistic shell of plasma moving (and accelerating) along the jet of a blazar, scattering on external photons emitted by the accretion disc and reprocessed in the broad-line region (BLR). The bulk Comptonization of disc photons is shown to yield a spectral comp…
The light curve of the companion to PSR B1957+20
Fruchter, A. S.; Torres, M. A. P.; Gibbons, R. A. +3 more
We present a new analysis of the light curve for the secondary star in the eclipsing binary millisecond pulsar system PSR B1957+20. Combining previous data and new data points at minimum from the Hubble Space Telescope, we have 100 per cent coverage in the R-band. We also have a number of new Ks-band data points, which we use to constra…
Environmental dependence of active galactic nuclei activity in the supercluster A901/2
Gray, M. E.; Wolf, C.; Meisenheimer, K. +5 more
We present XMM data for the supercluster A901/2, at z ~ 0.17, which is combined with deep imaging and 17-band photometric redshifts (from the COMBO-17 survey), two degree field (2dF) spectra and Spitzer 24µm data, to identify active galactic nuclei (AGN) in the supercluster. The 90 ksec XMM image contains 139 point sources, of which 11 are i…