Search Publications
Energy dependence of the band-limited noise in black hole X-ray binaries★
Stiele, H.; Yu, W.
Black hole low-mass X-ray binaries show a variety of variability features, which manifest as narrow peak-like structures superposed on broad noise components in power density spectra in the hard X-ray emission. In this work, we study variability properties of the band-limited noise component during the low-hard state for a sample of black hole X-r…
Origins of massive field stars in the Galactic Centre: a spectroscopic study
Morris, Mark R.; Wang, Q. Daniel; Dong, Hui +2 more
Outside of the known star clusters in the Galactic Centre, a large number of evolved massive stars have been detected; but their origins remain uncertain. We present a spectroscopic study of eight such stars, based on new Gemini Near-Infrared Spectrograph (GNIRS) and Near-IR Integral Field Spectrograph (NIFS) near-infrared observations. This work …
3C 57 as an atypical radio-loud quasar: implications for the radio-loud/radio-quiet dichotomy
Marziani, P.; Stirpe, G. M.; del Olmo, A. +4 more
Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichot…
Relationship between X-ray spectral index and X-ray Eddington ratio for Mrk 335 and Ark 564
Misra, R.; Tripathi, S.; Pathak, A. +3 more
We present a comprehensive flux-resolved spectral analysis of the bright narrow-line Seyfert 1 AGNs, Mrk 335 and Ark 564 using observations by XMM-Newton satellite. The mean and the flux-resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low-energy soft excess and the other for the high-energ…
Discovery of near-ultraviolet counterparts to millisecond pulsars in the globular cluster 47 Tucanae
Wijnands, R.; Rivera-Sandoval, L. E.; van den Berg, M. +11 more
We report the discovery of the likely white dwarf companions to radio millisecond pulsars 47 Tuc Q and 47 Tuc S in the globular cluster 47 Tucanae. These blue stars were found in near-ultraviolet images from the Hubble Space Telescope for which we derived accurate absolute astrometry, and are located at positions consistent with the radio coordina…
A high-resolution wide-field radio survey of M51
Argo, M. K.; Soria, R.; Tingay, S. J. +4 more
We present the highest resolution, wide-field radio survey of a nearby face-on star-forming galaxy to date. The multiphase centre technique is used to survey the entire disc of M51 (77 arcmin2) at a maximum resolution of 5 mas on a single 8 h pointing with the European Very Long Baseline Interferometry (VLBI) Network at 18 cm. In total,…
Energy-dependent orbital phases in NGC 300 X-1
Williams, B. F.; Binder, B.; Gross, J. +1 more
NGC 300 X-1 is a Wolf-Rayet (WR)+black hole binary that exhibits periodic decreases in X-ray flux. We present two new observations of NGC 300 X-1 from the Chandra X-ray Observatory (totalling ∼130 ks) along with Advanced Camera for Surveys imaging data from the Hubble Space Telescope (HST). We observe significant short-term variability in the X-ra…
Warm gas in and around simulated galaxy clusters as probed by absorption lines
Putman, M. E.; Emerick, A.; Bryan, G.
Understanding gas flows into and out of the most massive dark matter structures in our Universe, galaxy clusters, is fundamental to understanding their evolution. Gas in clusters is well studied in the hot (> 106 K) and cold (< 104 K) regimes, but the warm gas component (104-106 K) is poorly constr…
Reaching the peak of the quasar spectral energy distribution - I. Observations and models
Done, Chris; Elvis, Martin; McDowell, Jonathan C. +3 more
We perform a spectral analysis of a sample of 11 medium redshift (1.5 ≲ z ≲ 2.2) quasars. Our sample all have optical spectra from the SDSS, infrared spectra from GNIRS and TripleSpec, and X-ray spectra from XMM-Newton. We first analyse the Balmer broad emission line profiles which are shifted into the IR spectra to constrain black hole masses. Th…
Discovery of a quasi-periodic oscillation in the ultraluminous X-ray source IC 342 X-1: XMM-Newton results
Agrawal, V. K.; Nandi, Anuj
We report the discovery of a quasi-periodic oscillation (QPO) at 642 mHz in an XMM-Newton observation of the ultraluminous X-ray source (ULX) IC 342 X-1. The QPO has a centroid at νQPO = 642 ± 20 mHz, a coherence factor Q = 11.6 and an amplitude (rms) of 4.1 per cent with significance of 3.6σ. The energy dependence study shows that the …