Search Publications
The Compton hump and variable blue wing in the extreme low-flux NuSTAR observations of 1H0707-495
Harrison, F. A.; Stern, D.; Zhang, W. W. +10 more
The narrow-line Seyfert I galaxy, 1H0707-495, has been well observed in the 0.3-10 keV band, revealing a dramatic drop in flux in the iron Kα band, a strong soft excess, and short time-scale reverberation lags associated with these spectral features. In this paper, we present the first results of a deep 250-ks NuSTAR (Nuclear Spectroscopic Telesco…
Integrated light chemical tagging analyses of seven M31 outer halo globular clusters from the Pan-Andromeda Archaeological Survey
Dotter, Aaron; Venn, Kim A.; Sakari, Charli M. +4 more
Detailed chemical abundances are presented for seven M31 outer halo globular clusters (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated light spectra taken with the Hobby-Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS) - this pap…
New constraints on the star formation history of the star cluster NGC 1856
Goudfrooij, Paul; Puzia, Thomas H.; Correnti, Matteo +1 more
We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (age ∼ 300 Myr) star cluster NGC 1856 in the Large Magellanic Cloud. We compare the observed colour-magnitude diagram (CMD), after having applied a correction for differential reddening, with Monte Carlo simulations of simple s…
Simultaneous spectral and reverberation modelling of relativistic reflection in Mrk 335
Chainakun, P.; Young, A. J.
We present an X-ray spectral and timing model to investigate the broad and variable iron line seen in the high flux state of Mrk 335. The model consists of a variable X-ray source positioned along the rotation axis of the black hole that illuminates the accretion disc producing a back-scattered, ionized reflection spectrum. We compute time lags in…
On the interpretation of sub-giant branch morphologies of intermediate-age star clusters with extended main sequence turnoffs
Girardi, Léo; Marigo, Paola; Goudfrooij, Paul +4 more
High-quality photometry of many star clusters in the Magellanic Clouds with ages of 1-2 Gyr revealed main sequence turnoffs (MSTOs) that are significantly wider than can be accounted for by a simple stellar population (SSP). Such extended MSTOs (eMSTOs) are often interpreted in terms of an age spread of several 108 yr, challenging the t…
Kuiper belt structure around nearby super-Earth host stars
Matthews, Brenda C.; Wyatt, Mark C.; Udry, Stéphane +9 more
We present new observations of the Kuiper belt analogues around HD 38858 and HD 20794, hosts of super-Earth mass planets within 1 au. As two of the four nearby G-type stars (with HD 69830 and 61 Vir) that form the basis of a possible correlation between low-mass planets and debris disc brightness, these systems are of particular interest. The disc…
Was the soft X-ray flare in NGC 3599 due to an AGN disc instability or a delayed tidal disruption event?
Read, A. M.; Komossa, S.; Motta, S. E. +1 more
We present unpublished data from a tidal disruption candidate in NGC 3599 which show that the galaxy was already X-ray bright 18 months before the measurement which led to its classification. This removes the possibility that the flare was caused by a classical, fast-rising, short-peaked, tidal disruption event. Recent relativistic simulations ind…
SXP 5.05 = IGR J00569-7226: using X-rays to explore the structure of a Be star's circumstellar disc
Haberl, F.; Udalski, A.; Bartlett, E. S. +5 more
On MJD 56590-1 (2013 Oct 25-26), observations of the Magellanic Clouds by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory discovered a previously unreported bright, flaring X-ray source. This source was initially given the identification IGR J00569-7226. Subsequent multiwavelength observations identified the system as ne…
Effects of the variability of the nucleus of NGC 1275 on X-ray observations of the surrounding intracluster medium
Fabian, A. C.; Pinto, C.; Russell, H. R. +2 more
The active galaxy NGC 1275 lies at the centre of the Perseus cluster of galaxies, which is the X-ray brightest cluster in the Sky. The nucleus shows large variability over the past few decades. We compile a light curve of its X-ray emission covering about 40 years and show that the bright phase around 1980 explains why the inner X-ray bubbles were…
The morphology of the sub-giant branch and red clump reveal no sign of age spreads in intermediate-age clusters
Bastian, N.; Niederhofer, F.
A recent surprise in stellar cluster research, made possible through the precision of Hubble Space Telescope photometry, was that some intermediate-age (1-2 Gyr) clusters in the Large and Small Magellanic Clouds have main-sequence turn-off (MSTO) widths that are significantly broader than would be expected for a simple stellar population (SSP). On…