Search Publications
A systematic search for changing-look quasars in SDSS
Ross, Nicholas P.; Magnier, Eugene; Horne, Keith +10 more
We present a systematic search for changing-look quasars based on repeat photometry from Sloan Digital Sky Survey (SDSS) and Pan-STARRS1, along with repeat spectra from SDSS and SDSS-III Baryon Oscillation Spectroscopic Survey. Objects with large, |Δg| > 1 mag photometric variations in their light curves are selected as candidates to look for c…
A global look at X-ray time lags in Seyfert galaxies
Fabian, A. C.; Reynolds, C. S.; Uttley, P. +4 more
X-ray reverberation, where light-travel time delays map out the compact geometry around the inner accretion flow in supermassive black holes, has been discovered in several of the brightest, most variable and well-known Seyfert galaxies. In this work, we expand the study of X-ray reverberation to all Seyfert galaxies in the XMM-Newton archive abov…
A quasi-periodic modulation of the iron line centroid energy in the black hole binary H1743-322
Ingram, Adam; Done, Chris; Middleton, Matthew +5 more
Accreting stellar-mass black holes often show a `Type-C' quasi-periodic oscillation (QPO) in their X-ray flux and an iron emission line in their X-ray spectrum. The iron line is generated through continuum photons reflecting off the accretion disc, and its shape is distorted by relativistic motion of the orbiting plasma and the gravitational pull …
The effects of high density on the X-ray spectrum reflected from accretion discs around black holes
Steiner, James F.; Fabian, Andrew C.; McClintock, Jeffrey E. +5 more
Current models of the spectrum of X-rays reflected from accretion discs around black holes and other compact objects are commonly calculated assuming that the density of the disc atmosphere is constant within several Thomson depths from the irradiated surface. An important simplifying assumption of these models is that the ionization structure of …
The KMOS AGN Survey at High redshift (KASHz): the prevalence and drivers of ionized outflows in the host galaxies of X-ray AGN
Alexander, D. M.; Bauer, F. E.; Swinbank, A. M. +7 more
We present the first results from the KMOS (K-band Multi-Object Spectrograph) AGN (active galactic nuclei) Survey at High redshift (KASHz), a VLT/KMOS integral-field spectroscopic (IFS) survey of z ≳ 0.6 AGN. We present galaxy-integrated spectra of 89 X-ray AGN (L2-10 keV = 1042-1045 erg s-1), for which …
The discovery, monitoring and environment of SGR J1935+2154
Campana, S.; Tiengo, A.; Götz, D. +13 more
We report on the discovery of a new member of the magnetar class, SGR J1935+2154, and on its timing and spectral properties measured by an extensive observational campaign carried out between 2014 July and 2015 March with Chandra and XMM-Newton (11 pointings). We discovered the spin period of SGR J1935+2154 through the detection of coherent pulsat…
NuSTAR catches the unveiling nucleus of NGC 1068
Harrison, F. A.; Stern, D.; Alexander, D. M. +15 more
We present a NuSTAR and XMM-Newton monitoring campaign in 2014/2015 of the Compton-thick Seyfert 2 galaxy, NGC 1068. During the 2014 August observation, we detect with NuSTAR a flux excess above 20 keV (32 ± 6 per cent) with respect to the 2012 December observation and to a later observation performed in 2015 February. We do not detect any spectra…
The extraordinary amount of substructure in the Hubble Frontier Fields cluster Abell 2744
Kneib, J. -P.; Egami, E.; Eckert, D. +21 more
We present a joint optical/X-ray analysis of the massive galaxy cluster Abell 2744 (z = 0.308). Our strong- and weak-lensing analysis within the central region of the cluster, I.e. at R < 1 Mpc from the brightest cluster galaxy, reveals eight substructures, including the main core. All of these dark matter haloes are detected with a significanc…
Measuring the dynamical state of Planck SZ-selected clusters: X-ray peak - BCG offset
Bersanelli, M.; Maino, D.; Rossetti, M. +6 more
We want to characterize the dynamical state of galaxy clusters detected with the Sunyaev-Zeldovich (SZ) effect by Planck and compare them with the dynamical state of clusters selected in X-rays survey. We analysed a representative subsample of the Planck SZ catalogue, containing the 132 clusters with the highest signal to noise ratio and character…
A spectroscopic survey of X-ray-selected AGNs in the northern XMM-XXL field
Georgakakis, A.; Salvato, M.; Buchner, J. +10 more
This paper presents a survey of X-ray-selected active galactic nuclei (AGNs) with optical spectroscopic follow-up in a ∼ 18 deg2 area of the equatorial XMM-XXL north field. A sample of 8445 point-like X-ray sources detected by XMM-Newton above a limiting flux of F_{0.5-10 keV} > 10^{-15} erg cm^{-2} s^{-1} was matched to optical (Slo…