Search Publications
A connection between accretion states and the formation of ultrarelativistic outflows in a neutron star X-ray binary
Motta, S. E.; Fender, R. P.
The nearby accreting neutron star binary Sco X-1 is the closest example of ongoing relativistic jet production at high Eddington ratios. Previous radio studies have revealed that alongside mildly relativistic, radio-emitting ejecta, there is at times a much faster transfer of energy from the region of the accretion flow along the jet. The nature o…
Mapping the stability of stellar rotating spheres via linear response theory
Pichon, C.; Heggie, D. C.; Varri, A. L. +3 more
Rotation is ubiquitous in the Universe, and recent kinematic surveys have shown that early-type galaxies and globular clusters are no exception. Yet the linear response of spheroidal rotating stellar systems has seldom been studied. This paper takes a step in this direction by considering the behaviour of spherically symmetric systems with differe…
The Random Transiter - EPIC 249706694/HD 139139
Dai, F.; Vanderburg, A.; Jenkins, J. M. +16 more
We have identified a star, EPIC 249706694 (HD 139139), that was observed during K2 Campaign 15 with the Kepler extended mission that appears to exhibit 28 transit-like events over the course of the 87-d observation. The unusual aspect of these dips, all but two of which have depths of 200 ± 80 ppm, is that they exhibit no periodicity, and their ar…
Low-frequency X-ray timing with Gaussian processes and reverberation in the radio-loud AGN 3C 120
Wilkins, D. R.
A framework is developed to perform Fourier-domain timing analysis on X-ray light curves with gaps, employing Gaussian processes to model the probability distribution underlying the observed time series from which continuous samples can be drawn. A technique is developed to measure X-ray reverberation from the inner regions of accretion discs arou…
Nuclear kinematics in nearby AGN - I. An ALMA perspective on the morphology and kinematics of the molecular CO(2-1) emission
Storchi-Bergmann, T.; Schnorr-Müller, A.; Robinson, A. +6 more
We present the molecular gas morphology and kinematics of seven nearby Seyfert galaxies obtained from our 230 GHz ALMA observations. The CO J = 2-1 kinematics within the inner ∼30 arcsec (≲9 kpc) reveals rotation patterns that have been explored using the Bertola rotation model and a modified version of the Kinemetry package. The latter algorithm …
X-ray reverberation lags of the Fe-K line due to AGN disc winds
Done, Chris; Tsujimoto, Masahiro; Ebisawa, Ken +3 more
Short X-ray reverberation lags are seen across a broad Fe-K energy band in more than 20 active galactic nuclei (AGNs). This broad iron line feature in the lag spectrum is most significant in super-Eddington sources such as Ark 564 (L/LEdd ∼ 1) and 1H 0707-495 (L/LEdd ≳ 10). The observed lag time-scales correspond to very shor…
The long outburst of the black hole transient GRS 1716-249 observed in the X-ray and radio band
Motta, S. E.; Segreto, A.; Malzac, J. +9 more
We present the spectral and timing analysis of X-ray observations performed on the Galactic black hole transient GRS 1716-249 during the 2016-2017 outburst. The source was almost continuously observed with the Neil Gehrels Swift Observatory from 2016 December until 2017 October. The X-ray hardness ratio and timing evolution indicate that the sourc…
Quantifying the suppression of the (un)-obscured star formation in galaxy cluster cores at 0.2≲ z ≲0.9
Rodighiero, G.; Valtchanov, I.; Franceschini, A. +21 more
We quantify the star formation (SF) in the inner cores (R/R200 ≤0.3) of 24 massive galaxy clusters at 0.2≲ z ≲0.9 observed by the Herschel Lensing Survey and the Cluster Lensing and Supernova survey with Hubble. These programmes, covering the rest-frame ultraviolet to far-infrared regimes, allow us to accurately characterize stellar mas…
The backscattering ratio of comet 67P/Churyumov-Gerasimenko dust coma as seen by OSIRIS onboard Rosetta
Lara, L. M.; Bertaux, J. -L.; Lamy, P. +47 more
Remote sensing observations of dust particles ejected from comets provide important hints on the intimate nature of the materials composing these primitive objects. The measurement of dust coma backscattering ratio, BSR, defined as the ratio of the reflectance at phase angle 0° and 30°, helps tuning theoretical models aimed at solving the inverse …
The Kitt Peak Electron Multiplying CCD demonstrator
Kulkarni, S. R.; Duev, Dmitry A.; Riddle, Reed +10 more
The Kitt Peak Electron Multiplying CCD (EMCCD) demonstrator is a new instrument that has been developed for use at the Kitt Peak National Observatory's 84-inch telescope. The EMCCD enables single-band optical imaging in the Sloan g and r bands and Johnson UVRI filters. The EMCCD is chosen for its sub-electron effective read noise using large multi…