Search Publications
GW Librae: a unique laboratory for pulsations in an accreting white dwarf
Knigge, C.; Hermes, J. J.; Gänsicke, B. T. +22 more
Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmi…
The CHARA Array resolves the long-period Wolf-Rayet binaries WR 137 and WR 138
Gies, Douglas R.; Moffat, Anthony F. J.; Richardson, Noel D. +10 more
We report on interferometric observations with the CHARA Array of two classical Wolf-Rayet (WR) stars in suspected binary systems, namely WR 137 and WR 138. In both cases, we resolve the component stars to be separated by a few milliarcseconds. The data were collected in the H band, and provide a measure of the fractional flux for both stars in ea…
Morphological evolution of cluster red sequence galaxies in the past 9 Gyr
De Propris, Roberto; Phillipps, Steven; Bremer, Malcolm N.
Galaxies arrive on the red sequences of clusters at high redshift (z > 1) once their star formation is quenched and evolve passively thereafter. However, we have previously found that cluster red sequence galaxies (CRSGs) undergo significant morphological evolution subsequent to the cessation of star formation, at some point in the past 9-10 Gy…
EXTraS discovery of an 1.2-s X-ray pulsar in M 31
Salvaterra, R.; Haberl, F.; Read, A. M. +13 more
During a search for coherent signals in the X-ray archival data of XMM-Newton, we discovered a modulation at 1.2 s in 3XMM J004301.4+413017 (3X J0043), a source lying in the direction of an external arm of M 31. This short period indicates a neutron star (NS). Between 2000 and 2013, the position of 3X J0043 was imaged by public XMM-Newton observat…
X-ray timing analysis of the quasar PG 1211+143
Vaughan, S.; Reeves, J. N.; Pounds, K. +1 more
We report on a timing analysis of a new ∼630 ks XMM-Newton observation of the quasar, PG 1211+143. We find a well-defined X-ray power spectrum with a well-detected bend at ∼7 × 10-5 Hz, consistent with the established tbend-MBH correlation for luminous, accreting black holes. We find the linear rms-flux relation co…
Quantifying substructures in Hubble Frontier Field clusters: comparison with ΛCDM simulations
Liesenborgs, Jori; Mohammed, Irshad; Saha, Prasenjit +2 more
The Hubble Frontier Fields (HFFs) are six clusters of galaxies, all showing indications of recent mergers, which have recently been observed for lensed images. As such they are the natural laboratories to study the merging history of galaxy clusters. In this work, we explore the 2D power spectrum of the mass distribution PM(k) as a meas…
Absorption at 11 µm in the interstellar medium and embedded sources: evidence for crystalline silicates
Wright, Christopher M.; Do Duy, Tho; Lawson, Warrick
An absorption feature is occasionally reported around 11 µm in astronomical spectra, including those of forming stars. Candidate carriers include water ice, polycyclic aromatic hydrocarbons, silicon carbide, crystalline silicates or even carbonates. All are known constituents of cosmic dust in one or more types of environments, though not ne…
Bayesian analysis of two stellar populations in Galactic globular clusters- III. Analysis of 30 clusters
Jefferys, W. H.; Stenning, D. C.; Wagner-Kaiser, R. +5 more
We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of 30 Galactic globular clusters to characterize two distinct stellar populations. A sophisticated Bayesian technique is employed to simultaneously sample the joint posterior distribution of age, distance, and extinction for each cluster, as well a…
Nereid from space: rotation, size and shape analysis from K2, Herschel and Spitzer observations
Pál, A.; Molnár, L.; Müller, T. G. +8 more
In this paper, we present an analysis of K2 mission Campaign 3 observations of the irregular Neptune satellite, Nereid. We determined a rotation period of P = 11.594±0.017 h and amplitude of Δm = 0.0328m ± 0.0018m, confirming previous short rotation periods obtained in ground-based observations. The similarities of light-curve amplitudes between 2…
Luminosity-dependent change of the emission diagram in the X-ray pulsar 4U 1626-67
Gilfanov, Marat; Koliopanos, Filippos
We detect variability of the Fe K α emission line in the spectrum of X-ray pulsar 4U 1626-67, correlated with changes in its luminosity and in the shape of its pulse profile. Analysis of archival Chandra and RXTE observations revealed the presence of an intrinsically narrow Fe K α emission line in the spectrum obtained during the source's current …