Search Publications
Accretion flow diagnostics with X-ray spectral timing: the hard state of SWIFT J1753.5-0127
Maccarone, T. J.; Uttley, P.; Cassatella, P.
Recent XMM-Newton studies of X-ray variability in the hard states of black hole X-ray binaries (BHXRBs) indicate that the variability is generated in the 'standard' optically thick accretion disc that is responsible for the multi-colour blackbody emission. The variability originates in the disc as mass-accretion fluctuations and propagates through…
The properties of the brightest Lyα emitters at z=5.7
Schaerer, D.; Meisenheimer, K.; Lidman, C. +5 more
We use deep Very Large Telescope (VLT) optical and near-infrared spectroscopy and deep Spitzer/IRAC imaging to examine the properties of two of the most luminous Lyα emitters at z= 5.7. The continuum redward of the Lyα line is clearly detected in both objects, thus facilitating a relatively accurate measurement (10-20 per cent uncertainties) of th…
Variable stars in the Cetus dwarf spheroidal galaxy: population gradients and connections with the star formation history
Stetson, P. B.; Bono, G.; Fiorentino, G. +7 more
We investigate the variable star content of the isolated, Local Group, dwarf spheroidal (dSph) galaxy Cetus. Multi-epoch, wide-field images collected with the Very Large Telescope/Visible Multiobject Spectrograph camera allowed us to detect 638 variable stars (630 RR Lyrae stars and eight anomalous Cepheids), 475 of which are new detections. We pr…
X-ray colour-colour selection for heavily absorbed active galactic nuclei
Nandra, Kirpal; Brightman, Murray
We present a method for the identification of heavily absorbed active galactic nuclei (AGN) (NH > 1023 cm-2) from X-ray photometric data. We do this using a set of XMM-Newton reference spectra of local galaxies for which we have accurate NH information, as described in Brightman & Nandra. The tech…
Residual cooling and persistent star formation amid active galactic nucleus feedback in Abell 2597
Fabian, A. C.; Combes, F.; Salomé, P. +18 more
New Chandra X-ray and Herschel Far-Infrared (FIR) observations enable a multiwavelength study of active galactic nucleus (AGN) heating and intracluster medium (ICM) cooling in the brightest cluster galaxy (BCG) of Abell 2597 (z= 0.0821). The new Chandra observations reveal the central ≲30 kpc X-ray cavity network to be more extensive than previous…
Evolution of the spectral curvature in the ultraluminous X-ray source Holmberg II X-1
Kaaret, P.; Farrell, S. A.; Poutanen, J. +2 more
Ultraluminous X-ray sources (ULXs) are interesting systems as they can host intermediate-mass black holes. Alternatively, ULXs can represent stellar mass black holes accreting at super-Eddington rates. Recently, spectral curvature or breaks at energies above a few keV have been detected in high-quality ULX spectra. These spectral features have bee…
The luminosity function and stellar mass-to-light ratio of the massive globular cluster NGC 2419
Dalessandro, E.; Bellazzini, M.; Ibata, R. +1 more
We used archival Hubble Space Telescope Wide Field Camera 3 (WFC3) images to obtain the luminosity function of the remote globular cluster NGC 2419 from 2 mag above the horizontal branch level down to ≃ 3.0 mag below the turn-off point (to MI≃ 6.4), approximately covering the range of initial stellar masses ?. The completeness-corrected…
HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae
Klochkov, D.; Santangelo, A.; Quirrenbach, A. +191 more
The massive binary system Eta Carinae and the surrounding H II complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E≥ 100 GeV) γ-ray emission could be expected. This paper presents data collected during VHE γ-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orb…
New insights into the star formation histories of candidate intermediate-age early-type galaxies from K'-band imaging of globular clusters
Georgiev, Iskren Y.; Goudfrooij, Paul; Puzia, Thomas H.
We investigate the age and metallicity distributions of bright globular clusters (GCs) in the candidate intermediate-age early-type galaxies NGC 3610, 584 and 3377 using a combination of new Gemini's Near InfraRed Imager and Spectrometer K'-band imaging and existing optical VI photometry from Hubble Space Telescope data. The V-I versus I-K' colour…
Dwarf galaxies in the Coma cluster - I. Velocity dispersion measurements
Mobasher, B.; Tully, R. B.; Guzmán, R. +8 more
We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magn…