Search Publications
Isochrone fitting of Galactic globular clusters - IV. NGC 6362 and NGC 6723
Gontcharov, George A.; Mosenkov, Aleksandr V.; Khovritchev, Maxim Yu +10 more
We present new isochrone fits to the colour-magnitude diagrams of the Galactic globular clusters NGC 6362 and NGC 6723. We utilize 22 and 26 photometric filters for NGC 6362 and NGC 6723, respectively, from the ultraviolet to mid-infrared using data sets from Hubble Space Telescope, Gaia, unWISE, and other photometric sources. We use models and is…
Systematic errors in the maximum-likelihood regression of Poisson count data: introducing the overdispersed χ2 distribution
Bonamente, Massimiliano
This paper presents a new method to estimate systematic errors in the maximum-likelihood regression of count data. The method is applicable in particular to X-ray spectra in situations where the Poisson log-likelihood, or the Cash goodness-of-fit statistic, indicate a poor fit that is attributable to overdispersion of the data. Overdispersion in P…
Constraining the White-dwarf Mass and Magnetic Field Strength of a New Intermediate Polar through X-Ray Observations
Hailey, Charles J.; Mori, Kaya; Ramsay, Gavin +9 more
We report timing and broadband spectral analysis of a Galactic X-ray source, CXOGBS J174517.0-321356 (J1745), with a 614 s periodicity. Chandra discovered the source in the direction of the Galactic Bulge. Gong proposed that J1745 was either an intermediate polar (IP) with a mass of ~1 M ⊙, or an ultracompact X-ray binary (UCXB). To con…
Lensing in the Blue. II. Estimating the Sensitivity of Stratospheric Balloons to Weak Gravitational Lensing
Jauzac, Mathilde; Benton, Steven J.; Clark, Paul +23 more
The Superpressure Balloon-borne Imaging Telescope (SUPERBIT) is a diffraction-limited, wide-field, 0.5 m, near-infrared to near-ultraviolet observatory designed to exploit the stratosphere's space-like conditions. SUPERBIT's 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, w…
Dynamics in the outskirts of four Milky Way globular clusters: it's the tides that dominate
Lewis, Geraint F.; de Boer, Thomas; van der Marel, Roeland P. +17 more
We present the results of a spectroscopic survey of the outskirts of four globular - 1261, NGC 4590, NGC 1904, and NGC 1851 - covering targets within 1° from the cluster centres, with 2dF/AAOmega on the Anglo-Australian Telescope (AAT) and FLAMES on the very large telescope (VLT). We extracted chemo-dynamical information for individual stars, from…
X-ray properties of the white dwarf pulsar eRASSU J191213.9−441044
Marsh, T. R.; Schwope, A.; Pelisoli, I. +5 more
We report X-ray observations of the newly discovered pulsating white dwarf eRASSU J191213.9−441044 with Spectrum Roentgen Gamma and eROSITA (SRG/eROSITA) and XMM-Newton. The new source was discovered during the first eROSITA all-sky survey at a flux level of fX(0.2 − 2.3 keV) = 3.3 × 10−13 erg cm−2 s−1 a…
Inhomogeneous Galactic chemical evolution: modelling ultra-faint dwarf galaxies of the Large Magellanic Cloud
Jordan, C. J.; Vincenzo, F.; Ji, A. P. +3 more
Ultra-faint dwarf galaxies (UFDs) are among the oldest and most metal-poor galaxies in the cosmos, observed to contain no gas and a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the very first generations of stars. We present a novel inhomogeneous chemical evolution…
RR Lyrae stars as probes of the outer Galactic halo: chemical and kinematic analysis of a pilot sample
Grebel, Eva K.; Vivas, A. Katherina; Carlin, Jeffrey L. +4 more
We report the spectroscopic analysis of 20 halo ab-type RR Lyrae stars with heliocentric distances between 15 and 165 kpc, conducted using medium-resolution spectra from the Magellan Inamori Kyocera Echelle (MIKE) spectrograph. We obtain the systemic line-of-sight velocities of our targets with typical uncertainties of 5-10 km s-1 and c…
The First Survey of Quiet Sun Features Observed in Hard X-Rays with NuSTAR
Krucker, Säm; White, Stephen M.; Grefenstette, Brian W. +5 more
We present the first survey of quiet Sun features observed in hard X-rays (HXRs), using the Nuclear Spectroscopic Telescope ARray (NuSTAR), a HXR focusing optics telescope. The recent solar minimum, combined with NuSTAR's high sensitivity, has presented a unique opportunity to perform the first HXR imaging spectroscopy on a range of features in th…
Comparing Globular Cluster System Properties with Host Galaxy Environment
Ma, Chung-Pei; Greene, Jenny E.; Blakeslee, John P. +2 more
We present Hubble Space Telescope photometry in the optical (F475X) and near-infrared (F110W) bands of the globular cluster (GC) systems of the inner halos of a sample of 15 massive elliptical galaxies. The targets are selected from the volume-limited MASSIVE survey, and chosen to sample a range of environments from sparsely populated groups to th…