Search Publications
Accretion Geometry in the Hard State of the Black Hole X-Ray Binary MAXI J1820+070
Zdziarski, Andrzej A.; Szanecki, Michał; Niedźwiecki, Andrzej +2 more
We study X-ray spectra from the outburst rise of the accreting black hole binary MAXI J1820+070. We find that models having the disk inclinations within those of either the binary or the jet imply significant changes of the accretion disk inner radius during the luminous part of the hard spectral state, with that radius changing from >100 to ∼1…
Black Hole Mass Measurements of Radio Galaxies NGC 315 and NGC 4261 Using ALMA CO Observations
Ho, Luis C.; Barth, Aaron J.; Buote, David A. +6 more
We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 5 and Cycle 6 observations of CO (2-1) and CO (3-2) emission at 0"2-0"3 resolution in two radio-bright, brightest group/cluster early-type galaxies, NGC 315 and NGC 4261. The data resolve CO emission that extends within their black hole (BH) spheres of influence (rg), …
Stringent upper limit on Be star fractions produced by binary interaction
Wang, C.; Milone, A. P.; Schootemeijer, A. +2 more
Context. Binary evolution can result in fast-rotating stars through accretion of angular momentum during mass-transfer phases. These fast-rotating stars are predicted to be observable as Be stars. Current models struggle to produce a satisfactory description of Be star populations, even though numerous pieces of observational evidence indicate tha…
CON-quest. Searching for the most obscured galaxy nuclei
Greve, T. R.; Gallagher, J. S.; Onishi, K. +28 more
Context. Some luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) host extremely compact (r < 100 pc) and dusty nuclei. The high extinction associated with large column densities of gas and dust toward these objects render them hard to detect at many wavelengths. The intense infrared radiation arising from warm dust in these sources…
ACCESS and LRG-BEASTS: A Precise New Optical Transmission Spectrum of the Ultrahot Jupiter WASP-103b
Nikolov, Nikolay; Gibson, Neale P.; Wilson, Jamie +17 more
We present a new ground-based optical transmission spectrum of the ultrahot Jupiter WASP-103b ( ${T}_{\mathrm{eq}}=2484$ K). Our transmission spectrum is the result of combining five new transits from the ACCESS survey and two new transits from the LRG-BEASTS survey with a reanalysis of three archival Gemini/GMOS transits and one VLT/FORS2 transit…
A hidden population of high-redshift double quasars unveiled by astrometry
Shen, Yue; Oguri, Masamune; Lazio, Joseph +6 more
Galaxy mergers occur frequently in the early Universe1 and bring multiple supermassive black holes (SMBHs) into the nucleus, where they may eventually coalesce. Identifying post-merger-scale (that is, less than around a few kpc) dual SMBHs is a critical pathway to understanding their dynamical evolution and successive mergers2
The changing face of AU Mic b: stellar spots, spin-orbit commensurability, and transit timing variations as seen by CHEOPS and TESS
Guterman, P.; Alonso, R.; Deleuil, M. +78 more
AU Mic is a young planetary system with a resolved debris disc showing signs of planet formation and two transiting warm Neptunes near mean-motion resonances. Here we analyse three transits of AU Mic b observed with the CHaracterising ExOPlanet Satellite (CHEOPS), supplemented with sector 1 and 27 Transiting Exoplanet Survey Satellite (TESS) photo…
Exploring the Galaxy's halo and very metal-weak thick disc with SkyMapper and Gaia DR2
Schmidt, B. P.; Da Costa, G. S.; Milone, A. P. +16 more
In this work, we combine spectroscopic information from the SkyMapper survey for Extremely Metal-Poor stars and astrometry from Gaia DR2 to investigate the kinematics of a sample of 475 stars with a metallicity range of $-6.5 \le \rm [Fe/H] \le -2.05$ dex. Exploiting the action map, we identify 16 and 40 stars dynamically consistent with the Gaia …
Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories
Hilker, M.; Pinna, F.; de Zeeuw, P. T. +15 more
Nuclear star clusters (NSCs) are the densest stellar systems in the Universe and are found in the centres of all types of galaxies. They are thought to form via mergers of star clusters such as ancient globular clusters (GCs) that spiral to the centre as a result of dynamical friction or through in situ star formation directly at the galaxy centre…
Dynamically Tagged Groups of Very Metal-poor Halo Stars from the HK and Hamburg/ESO Surveys
Beers, Timothy C.; Lee, Young Sun; Placco, Vinicius M. +13 more
We analyze the dynamical properties of ∼1500 very metal-poor (VMP; [Fe/H] ≲ -2.0) halo stars, based primarily on medium-resolution spectroscopic data from the HK and Hamburg/ESO surveys. These data, collected over the past 30 yr, are supplemented by a number of calibration stars and other small samples, along with astrometric information from Gaia…