Search Publications
The kilohertz quasi-periodic oscillations during the Z and atoll phases of the unique transient XTE J1701-462
Homan, Jeroen; Belloni, Tomaso; Wijnands, Rudy +6 more
We analysed 866 observations of the neutron star low-mass X-ray binary XTE J1701-462 during its 2006-2007 outburst. XTE J1701-462 is the only example so far of a source that during an outburst showed, beyond any doubt, spectral and timing characteristics both of the Z and atoll type. There are 707 RXTE observations (~2.5 Ms) of the source in the Z…
Diamonds on the Hat: globular clusters in the Sombrero galaxy (M104)
Bailin, Jeremy; Spitler, Lee R.; Forbes, Duncan A. +1 more
Images from the Hubble Space Telescope Advanced Camera for surveys are used to carry out a new photometric study of the globular clusters (GCs) in M104, the Sombrero galaxy. The primary focus of our study is the characteristic distribution function of linear sizes [size distribution function (SDF)] of the GCs. We measure the effective radii for 65…
Searching for the inverse-Compton emission from bright cluster-centre radio galaxies
Hardcastle, M. J.; Croston, J. H.
We use deep archival Chandra and XMM-Newton observations of three of the brightest cluster-centre radio galaxies in the sky, Cygnus A, Hercules A and Hydra A, to search for inverse-Compton emission from the population of electrons responsible for the low-frequency radio emission. Using simulated observations, we derive robust estimates for the unc…
Constraining the low-mass end of the initial mass function with gravitational lensing
Courbin, Frédéric; Saha, Prasenjit; Ferreras, Ignacio +2 more
The low-mass end of the stellar initial mass function (IMF) is constrained by focusing on the baryon-dominated central regions of strong lensing galaxies. We study in this Letter the Einstein Cross (Q2237+0305), a z = 0.04 barred galaxy whose bulge acts as lens on a background quasar. The positions of the four quasar images constrain the surface m…
A new analysis of the short-duration, hard-spectrum GRB 051103, a possible extragalactic soft gamma repeater giant flare
Cline, T.; Hurley, K.; Yamaoka, K. +34 more
GRB 051103 is considered to be a candidate soft gamma repeater (SGR) extragalactic giant magnetar flare by virtue of its proximity on the sky to M81/M82, as well as its time history, localization and energy spectrum. We have derived a refined interplanetary network localization for this burst which reduces the size of the error box by over a facto…
X-ray reflection in a sample of X-ray bright ultraluminous X-ray sources
Fabian, A. C.; Caballero-García, M. D.
We apply a reflection-based model to the best available XMM-Newton spectra of X-ray bright ultraluminous X-ray sources (NGC 1313 X-1, NGC 1313 X-2, M 81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is apparent in the data of all the sources at energies 6-7keV. The drop is interpreted here in terms of relativistically bl…
Spatially resolved study of the physical properties of the ionized gas in NGC 595
Kennicutt, R. C.; Monreal-Ibero, A.; Relaño, M. +1 more
We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous HII regions in M33. This type of observations allows us to study the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral ra…
Searching for dark matter in X-rays: how to check the dark matter origin of a spectral feature
Boyarsky, Alexey; Ruchayskiy, Oleg; Iakubovskyi, Dmytro +3 more
A signal from decaying dark matter (DM) can be unambiguously distinguished from spectral features of astrophysical or instrumental origin by studying its spatial distribution. We demonstrate this approach by examining the recent claim of Loewenstein and Kusenko regarding the possible DM origin of the 2.5 keV line in Chandra observations of the Mil…
MACS J1423.8+2404: gravitational lensing by a massive, relaxed cluster of galaxies at z = 0.54
Kneib, J. -P.; Smith, G. P.; Schrabback, T. +8 more
We present results of a gravitational lensing and optical study of MACS J1423.8+2404 (z = 0.545, MACS J1423), the most relaxed cluster in the high-redshift subsample of clusters discovered in the MAssive Cluster Survey (MACS). Our analysis uses high-resolution images taken with the Hubble Space Telescope in the F555W and F814W passbands, ground-ba…
Stellar winds and mass loss from extreme helium stars
Hamann, W. -R.; Jeffery, C. S.
Extreme helium stars are very rare low-mass supergiants in a late stage of evolution. They are probably contracting to become white dwarfs following a violent phase of evolution which caused them to become hydrogen-deficient giants, possibly R CrB stars. Using the latest generation of models for spherically expanding stellar atmospheres, we set ou…