Search Publications
The defining characteristics of intermediate polars - the case of three-candidate systems
Ramsay, Gavin; Wheatley, Peter J.; Hakala, Pasi +2 more
Intermediate polars (IPs) are a group of cataclysmic variables (CVs) which are thought to contain white dwarfs which have a magnetic field strength in the range ~0.1-10MG. A significant fraction of the X-ray sources detected in recent deep surveys has been postulated to consist of IPs. Until now two of the defining characteristics of IPs have been…
Testing the blazar spectral sequence: X-ray-selected blazars
Maraschi, L.; Ghisellini, G.; Tavecchio, F. +2 more
We present simultaneous optical and X-ray data from Swift for a sample of radio-loud flat-spectrum quasars selected from the Einstein Medium Sensitivity Survey (EMSS). We present also a complete analysis of Swift and INTEGRAL data on four blazars recently discussed as possibly challenging the trends of the hypothesized `blazar spectral sequence'. …
The early-type galaxies NGC 1407 and NGC 1400 - II. Star formation and chemical evolutionary history
Forbes, Duncan A.; Proctor, Robert N.; Brough, Sarah +2 more
We present a possible star formation and chemical evolutionary history for two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as part of the Group Evolution Multi-wavelength Study.
Our analysis is based on new high signal-to-noise ratio spatial…ZEN2: a narrow J-band search for z ~ 9 Lyα emitting galaxies directed towards three lensing clusters
Kneib, J. -P.; Minniti, D.; Courbin, F. +1 more
We present the results of a continuing survey to detect Lyα emitting galaxies at redshifts z ~ 9: the `z equals nine' (ZEN) survey. We have obtained deep VLT Infrared Spectrometer and Array Camera observations in the narrow J-band filter NB119 directed towards three massive lensing clusters: Abell clusters 1689, 1835 and 114. The foreground cluste…
How rapidly do neutron stars spin at birth? Constraints from archival X-ray observations of extragalactic supernovae
Soria, Roberto; Stella, Luigi; Perna, Rosalba +1 more
Traditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at birth based on their X-ray luminosities. In particular, the observed luminosity distribution of supernovae (SNe) poses a constraint on the initial rot…
On the radial distribution of white dwarfs in the globular cluster NGC 6397
Anderson, J.; Davis, D. S.; King, I. R. +5 more
We have examined the radial distribution of white dwarfs over a single Hubble Space Telescope/Advanced Camera for Surveys field in the nearby globular cluster NGC 6397. In relaxed populations, such as in a globular cluster, stellar velocity dispersion, and hence radial distribution, is directly dependent on stellar masses. The progenitors of very …
Suzaku observations of Markarian 335: evidence for a distributed reflector
Larsson, J.; Ponti, G.; Fabian, A. C. +3 more
We report on a 151-ks net exposure Suzaku observation of the narrow-line Seyfert 1 galaxy Mrk 335. The 0.5-40 keV spectrum contains a broad Fe line, a strong soft excess below about 2 keV and a Compton hump around 20-30 keV. We find that a model consisting of a power law and two reflectors provides the best fit to the time-averaged spectrum. In th…
A bright, dust-obscured, millimetre-selected galaxy beyond the Bullet Cluster (1E0657-56)
Yun, M. S.; Kohno, K.; Wilson, G. W. +24 more
Deep 1.1mm continuum observations of 1E0657-56 (the `Bullet Cluster') taken with the millimeter-wavelength camera AzTEC on the 10-m Atacama Submillimeter Telescope Experiment (ASTE), have revealed an extremely bright (S1.1mm = 15.9mJy) unresolved source. This source, MMJ065837-5557.0, lies close to a maximum in the density of underlying…
Extending the baseline: Spitzer mid-infrared photometry of globular cluster systems in the Centaurus A and Sombrero Galaxies
Spitler, Lee R.; Forbes, Duncan A.; Beasley, Michael A.
Spitzer IR Array Camera (IRAC) mid-infrared photometry is presented for the globular cluster (GC) systems of the NGC 5128 (`Centaurus A') and NGC 4594 (`Sombrero') galaxies. Existing optical photometric and spectroscopic are combined with this new data in a comprehensive optical-to-mid-IR colour catalogue of 260 GCs. Empirical colour-metallicity r…
On contamination and completeness in z >= 5 Lyman-break galaxy surveys
Lehnert, Matthew D.; Stanway, Elizabeth R.; Bremer, Malcolm N.
A large population of z > 5 Lyman-break galaxies has been identified in recent years. However, the high-redshift galaxies selected by different surveys are subject to a variety of selection effects - some overt, others more subtle. We present an analysis of sample completeness and contamination issues in high-redshift surveys, focusing on surve…