Search Publications
The vertical metallicity gradients of mono-age stellar populations in the Milky Way with the RAVE and Gaia data
Cropper, Mark; Lin, Jane; Casagrande, Luca +3 more
We investigate the vertical metallicity gradients of five mono-age stellar populations between 0 and 11 Gyr for a sample of 18 435 dwarf stars selected from the cross-matched Tycho-Gaia Astrometric Solution and Radial Velocity Experiment (RAVE) Data Release 5. We find a correlation between the vertical metallicity gradients and age, with no vertic…
New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55
Negueruela, I.; Roche, P.; Tabernero, H. M. +3 more
As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55, and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation period…
Modelling the structure of star clusters with fractional Brownian motion
Whitworth, A. P.; Lomax, O.; Bates, M. L.
The degree of fractal substructure in molecular clouds can be quantified by comparing them with fractional Brownian motion (FBM) surfaces or volumes. These fields are self-similar over all length-scales and characterized by a drift exponent H, which describes the structural roughness. Given that the structure of molecular clouds and the initial st…
Made-to-measure modelling of observed galaxy dynamics
Bovy, Jo; Kawata, Daisuke; Hunt, Jason A. S.
Amongst dynamical modelling techniques, the made-to-measure (M2M) method for modelling steady-state systems is amongst the most flexible, allowing non-parametric distribution functions in complex gravitational potentials to be modelled efficiently using N-body particles. Here, we propose and test various improvements to the standard M2M method for…
The fast transient sky with Gaia
Jonker, Peter G.; van Leeuwen, Floor; Hodgkin, Simon T. +8 more
The ESA Gaia satellite scans the whole sky with a temporal sampling ranging from seconds and hours to months. Each time a source passes within the Gaia field of view, it moves over 10 charge coupled devices (CCDs) in 45 s and a light curve with 4.5 s sampling (the crossing time per CCD) is registered. Given that the 4.5 s sampling represents a vir…
Further constraints on neutron star crustal properties in the low-mass X-ray binary 1RXS J180408.9-342058
Degenaar, N.; Wijnands, R.; Parikh, A. S. +2 more
We report on two new quiescent XMM-Newton observations (in addition to the earlier Swift/XRT and XMM-Newton coverage) of the cooling neutron star crust in the low-mass X-ray binary 1RXS J180408.9-342058. Its crust was heated during the ∼4.5 month accretion outburst of the source. From our quiescent observations, fitting the spectra with a neutron …
Observations contradict galaxy size and surface brightness predictions that are based on the expanding universe hypothesis
Lerner, Eric J.
In a non-expanding universe, surface brightness is independent of distance or redshift, while in an expanding universe it decreases rapidly with both. Similarly, for objects of the same luminosity, the angular radius of an object in a non-expanding universe declines with redshift, while in an expanding universe this radius increases for redshifts …
A near-infrared variable star survey in the Magellanic Clouds: the Small Magellanic Cloud data
Nagata, Tetsuya; Tamura, Motohide; Matsunaga, Noriyuki +12 more
A very long-term near-infrared variable star survey towards the Large and Small Magellanic Clouds (LMC and SMC) was carried out using the 1.4 m InfraRed Survey Facility at the South African Astronomical Observatory. This project was initiated in 2000 December in the LMC, and in 2001 July in the SMC. Since then an area of 3 deg2 along th…
Infrared and X-ray study of the Galactic SNR G15.9+0.2
Klochkov, Dmitry; Sasaki, Manami; Santangelo, Andrea +2 more
G15.9+0.2 is a Galactic shell-type supernova remnant (SNR), which was detected in radio and has been confirmed in X-rays based on Chandra observations. An X-ray point source CXOUJ181852.0-150213 has been detected and suggested to be an associated neutron star. In a recent study, we have confirmed the source to be a central compact object (CCO). We…
FBQS J1644+2619: multiwavelength properties and its place in the class of γ-ray emitting Narrow Line Seyfert 1s
Larsson, J.; Piconcelli, E.; Falocco, S. +4 more
A small fraction of Narrow Line Seyfert 1s (NLSy1s) are observed to be γ-ray emitters. Understanding the properties of these sources is of interest since the majority of NLSy1s are very different from typical blazars. Here, we present a multifrequency analysis of FBQS J1644+2619, one of the most recently discovered γ-ray emitting NLSy1s. We analys…