Search Publications
Statistical microlensing towards magnified high-redshift star clusters
Dai, Liang
We study light variability of gravitationally magnified high-redshift star clusters induced by a foreground population of microlenses. This arises as the incoherent superposition of light variations from many source stars traversing the random magnification pattern on the source plane. The light curve resembles a scale-invariant, Gaussian process …
Collisions in a gas-rich white dwarf planetary debris disc
Hermes, J. J.; Gänsicke, Boris T.; von Hippel, Ted +5 more
WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3-5 $\mu$m flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. Stochastic brightening events superimposed on the decline in…
The GALAH survey: Chemical homogeneity of the Orion complex
Lewis, Geraint F.; Ting, Yuan-Sen; Buder, Sven +18 more
Due to its proximity, the Orion star forming region is often used as a proxy to study processes related to star formation and to observe young stars in the environment they were born in. With the release of Gaia DR2, the distance measurements to the Orion complex are now good enough that the 3D structure of the complex can be explored. Here we tes…
IGM transmission bias for z ≥ 2.9 Lyman continuum detected galaxies
Ryan-Weber, E. V.; Rafelski, M.; Bassett, R. +4 more
Understanding the relationship between the underlying escape fraction of Lyman continuum (LyC) photons (fesc) emitted by galaxies and measuring the distribution of observed fesc values at high redshift is fundamental to the interpretation of the reionization process. In this paper, we perform a statistical exploration of the …
NGTS-19b: a high-mass transiting brown dwarf in a 17-d eccentric orbit
Jackman, James A. G.; Wheatley, Peter J.; Bayliss, Daniel +34 more
We present the discovery of NGTS-19b, a high-mass transiting brown dwarf discovered by the Next Generation Transit Survey. We investigate the system using follow-up photometry from the South African Astronomical Observatory, as well as sector 11 Transiting Exoplanet Survey Satellite data, in combination with radial velocity measurements from the C…
Classification of 4XMM-DR9 sources by machine learning
Wu, Xue-Bing; Zhang, Yanxia; Zhao, Yongheng
The ESA's X-ray Multi-mirror Mission (XMM-Newton) created a new high-quality version of the XMM-Newton serendipitous source catalogue, 4XMM-DR9, which provides a wealth of information for observed sources. The 4XMM-DR9 catalogue is correlated with the Sloan Digital Sky Survey (SDSS) DR12 photometric data base and the AllWISE data base; we then get…
The evolution of rapid optical/X-ray timing correlations in the initial hard state of MAXI J1820+070
Dhillon, V. S.; Charles, P. A.; Misra, R. +11 more
We report on a multiepoch campaign of rapid optical/X-ray timing observations of the superbright 2018 outburst of MAXI J1820+070, a black hole low-mass X-ray binary system. The observations spanned 80 d in the initial hard state and were taken with NTT/ULTRACAM and GTC/HiPERCAM in the optical (usgsrsisz<…
Variability, periodicity, and contact binaries in WISE
Zakamska, Nadia L.; Chandra, Vedant; Hwang, Hsiang-Chih +2 more
The time-series component of Wide-field Infrared Survey Explorer (WISE) is a valuable resource for the study of variable objects. We present an analysis of an all-sky sample of ~450 000 AllWISE+NEOWISE infrared light curves of likely variables identified in AllWISE. By computing periodograms of all these sources, we identify ~56 000 periodic varia…
Fomalhaut b could be massive and sculpting the narrow, eccentric debris disc, if in mean-motion resonance with it
Booth, Mark; Krivov, Alexander V.; Faramaz, Virginie +4 more
The star Fomalhaut hosts a narrow, eccentric debris disc, plus a highly eccentric companion Fomalhaut b. It is often argued that Fomalhaut b cannot have significant mass, otherwise it would quickly perturb the disc. We show that material in internal mean-motion resonances with a massive, coplanar Fomalhaut b would actually be long-term stable, and…
Dating individual quasars with the He II proximity effect
Hennawi, Joseph F.; Worseck, Gábor; Prochaska, J. Xavier +2 more
Constraints on the time-scales of quasar activity are key to understanding the formation and growth of supermassive black holes (SMBHs), quasar triggering mechanisms, and possible feedback effects on their host galaxies. However, observational estimates of this so-called quasar lifetime are highly uncertain (tQ ~ 104-109…