Search Publications
Is there a fundamental upper limit to the mass of a star cluster?
Leaman, Ryan; Schinnerer, Eva; van de Ven, Glenn +2 more
The discovery around the turn of the millennium of a population of very massive (M⋆ > 2 × 106 M⊙) compact stellar systems (CSS) with physical properties (radius, velocity dispersion, stellar mass etc.) that are intermediate between those of the classical globular cluster (GC) population and galaxies led to quest…
Ultraviolet and optical spectroscopy of AGB stars showing UV excess
Guerrero, Martín A.; Ortiz, Roberto; Costa, Roberto D. D.
We have examined ultraviolet (UV) and optical UB spectra of 20 UV-emitting Asymptotic Giant Branch (AGB) stars of various variability classes to study the intensity of the continuum and emission lines as a function of stellar visual magnitude to shed light on the origin of their UV emission. A significant fraction (60 per cent) of these stars show…
Asteroseismic modelling of the subgiant µ Herculis using SONG data: lifting the degeneracy between age and model input parameters
Bedding, Timothy R.; Stello, Dennis; Deng, Licai +3 more
We model the oscillations of the SONG target µ Herculis to estimate the parameters of the star. The ℓ = 1 mixed modes of µ Her provide strong constraints on stellar properties. The mass and age given by our asteroseismic modelling are 1.10^{+0.11}_{-0.06} M⊙ and 7.55^{+0.96}_{-0.79} Gyr, respectively. The initial helium abun…
An extragalactic chromosome map: the intermediate-age SMC cluster Lindsay 1
Dalessandro, E.; Salaris, M.; Cabrera-Ziri, I. +8 more
The discovery of star-to-star abundance variations (a.k.a. multiple populations - MPs) within globular clusters (GCs), which are generally not found in the field or in lower mass open clusters, has led to a search for the unique property of GCs that allow them to host this phenomenon. Recent studies have shown that MPs are not limited to the ancie…
GMRT 610 MHz observations of galaxy clusters in the ACT equatorial sample
Hilton, Matt; Sifón, Cristóbal; Bond, J. Richard +11 more
We present Giant Metrewave Radio Telescope (GMRT) 610 MHz observations of 14 Atacama Cosmology Telescope (ACT) clusters, including new data for nine. The sample includes 73 per cent of ACT equatorial clusters with M500 > 5 × 1014 M⊙. We detect diffuse emission in three of these (27^{+20}_{-14} per cent): we dete…
Absolute properties of RU Cnc revisited: an active RS CVn-type eclipsing binary with red giant branch and main-sequence components
Koçak, D.; Yakut, K.; Çokluk, K. A. +3 more
We present observations and analysis of an RS CVn-type double-lined eclipsing binary system, RU Cnc. The system has been observed for over a century. High-quality long-cadence observations, newly obtained from the Kepler K2 C5 and C18 campaigns, and two radial velocity curves were combined and analysed simultaneously, assuming a multispot model. T…
The subgiant HR 7322 as an asteroseismic benchmark star
Huber, Daniel; Stokholm, Amalie; White, Timothy R. +5 more
We present an in-depth analysis of the bright subgiant HR 7322 (KIC 10005473) using Kepler short-cadence photometry, optical interferometry from CHARA, high-resolution spectra from SONG, and stellar modelling using GARSTEC grids, and the Bayesian grid-fitting algorithm BASTA. HR 7322 is only the second subgiant with high-quality Kepler asteroseism…
Testing the warmness of dark matter
Nunes, Rafael C.; Kumar, Suresh; Yadav, Santosh Kumar
Dark matter (DM) as a pressureless perfect fluid provides a good fit of the standard Λ cold dark matter (ΛCDM) model to the astrophysical and cosmological data. In this paper, we investigate two extended properties of DM: a possible time dependence of the equation of state of DM via Chevallier-Polarski-Linder parametrization, wdm = w
Searching for fast extragalactic X-ray transients in Chandra surveys
Bauer, F. E.; Brandt, W. N.; Xue, Y. Q. +4 more
Recent works have discovered two fast (≈10 ks) extragalactic X-ray transients in the Chandra Deep Field-South (CDF-S XT1 and XT2). These findings suggest that a large population of similar extragalactic transients might exist in archival X-ray observations. We develop a method that can effectively detect such transients in a single Chandra exposur…
The XUV irradiation and likely atmospheric escape of the super-Earth π Men c
Wheatley, Peter J.; Bourrier, Vincent; Ehrenreich, David +1 more
π Men c was recently announced as the first confirmed exoplanet from the TESS mission. The planet has a radius of just 2 R⊕ and it transits a nearby Sun-like star of naked-eye brightness, making it the ideal target for atmospheric characterization of a super-Earth. Here we analyse archival ROSAT and Swift observations of π Men in order …