Search Publications
Correlated X-ray/ultraviolet/optical variability in the very low mass AGN NGC 4395
McHardy, I.; Breedt, E.; Uttley, P. +4 more
We report the results of a 1-yr Swift X-ray/ultraviolet (UV)/optical programme monitoring the dwarf Seyfert nucleus in NGC 4395 in 2008-2009. The UV/optical flux from the nucleus was found to vary dramatically over the monitoring period, with a similar pattern of variation in each of the observed UV/optical bands (spanning 1900-5500 Å). In particu…
Discovery of the millisecond pulsar PSR J2043+1711 in a Fermi source with the Nançay Radio Telescope
Camilo, F.; Guillemot, L.; Harding, A. K. +18 more
We report the discovery of the millisecond pulsar PSR J2043+1711 in a search of a Fermi Large Area Telescope (LAT) source with no known associations, with the Nançay Radio Telescope. The new pulsar, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (? kpc) and is in a 1.48-d orbit around a low-mass compani…
Stars, dust, and the growth of ultraviolet-selected sub-L* galaxies at redshift z∼ 2
Sawicki, Marcin
This work concerns the physical properties of very faint (?= 28 AB mag; Mstars,lim∼ 108 M⊙), ultraviolet-selected (UV-selected) sub-L* BX galaxies at z∼ 2.3. Stellar masses, dust content and dust-corrected star formation rates are constrained using broad-band spectral energy distribution fitting, resulting in a num…
Testing cosmology with extreme galaxy clusters
Harrison, Ian; Coles, Peter
Motivated by recent suggestions that a number of observed galaxy clusters have masses which are too high for their given redshift to occur naturally in a standard model cosmology, we use extreme value statistics to construct confidence regions in the mass-redshift plane for the most extreme objects expected in the universe. We show how such a diag…
A Giant Metrewave Radio Telescope/Chandra view of IRAS 09104+4109: a type 2 QSO in a cooling flow
Donahue, Megan; Hoekstra, Henk; Babul, Arif +8 more
IRAS 09104+4109 is a rare example of a dust enshrouded type 2 quasi-stellar object (QSO) in the centre of a cool-core galaxy cluster. Previous observations of this z = 0.44 system showed that, as well as powering the hyperluminous infrared emission of the cluster-central galaxy, the QSO is associated with a double-lobed radio source. However, the …
Further X-ray observations of the galaxy cluster PKS 0745-191 to the virial radius and beyond
Fabian, A. C.; Sanders, J. S.; Walker, S. A. +1 more
We use new Suzaku observations of PKS 0745-191 to measure the thermodynamic properties of its intracluster medium (ICM) out to and beyond r200 (reaching 1.25r200) with better accuracy than previously achieved, owing to a more accurate and better understood background model. We investigate and resolve the tensions between the …
Photometric determination of the mass accretion rates of pre-mainsequence stars - III. Results in the Large Magellanic Cloud
Panagia, N.; De Marchi, G.; Sicilia-Aguilar, A. +2 more
We present a multi-wavelength study of three star forming regions, spanning the age range 1-14 Myr, located between the 30 Doradus complex and supernova SN1987A in the Large Magellanic Cloud (LMC). We reliably identify about 1000 pre-main sequence (PMS) star candidates actively undergoing mass accretion and estimate their stellar properties and ma…
The effect of frame dragging on the iron Kα line in X-ray binaries
Ingram, Adam; Done, Chris
The clear characteristic time-scale picked out by the low-frequency quasi-periodic oscillations (QPOs) seen in many black hole and neutron star binaries has the potential to provide a very powerful diagnostic of the inner regions of the accretion flow. However, this potential cannot be realized without a quantitative model for the QPO. We have rec…
Modelling the very high energy flare of 3C 279 using one-zone leptonic model
Godambe, S.; Sahayanathan, S.
We model the simultaneous observations of the flat-spectrum radio quasar 3C 279 at radio, optical, X-ray and very high energy (VHE) gamma-ray energies during 2006 flare using a simple one-zone leptonic model. We consider synchrotron emission due to cooling of a non-thermal electron distribution in an equipartition magnetic field and inverse Compto…
The velocity dispersion and mass function of the outer halo globular cluster Palomar 4
Djorgovski, S. G.; Grebel, Eva K.; Côté, Patrick +5 more
We obtained precise line-of-sight radial velocities of 23 member stars of the remote halo globular cluster Palomar 4 (Pal 4) using the High Resolution Echelle Spectrograph at the Keck I telescope. We also measured the mass function of the cluster down to a limiting magnitude of V∼ 28 mag using archival Hubble Space Telescope/Wide Field Planetary C…