Search Publications
Globular cluster systems in nearby dwarf galaxies - I. HST/ACS observations and dynamical properties of globular clusters at low environmental density
Georgiev, Iskren Y.; Goudfrooij, Paul; Puzia, Thomas H. +1 more
We investigate the old globular cluster (GC) population of 68 faint (MV > -16mag) dwarf galaxies located in the halo regions of nearby (<~12Mpc) loose galaxy groups and in the field environment based on archival Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) images in F606W and F814W filters. The combined colour di…
Constraining jet/disc geometry and radiative processes in stellar black holes XTE J1118+480 and GX 339-4
Nowak, Michael; Wilms, Jörn; Markoff, Sera +3 more
We present results from modelling of quasi-simultaneous broad-band (radio through X-ray) observations of the Galactic stellar black hole (BH) transient X-ray binary (XRB) systems XTE J1118+480 and GX 339-4 using an irradiated disc + compact jet model. In addition to quantifying the physical properties of the jet, we have developed a new irradiated…
A surprisingly high pair fraction for extremely massive galaxies at z ~ 3 in the GOODS NICMOS survey
Papovich, Casey; Dickinson, Mark; Conselice, Christopher J. +4 more
We calculate the major pair fraction and derive the major merger fraction and rate for 82 massive (M* > 1011Msolar) galaxies at 1.7 < z < 3.0 utilizing deep Hubble Space Telescope NICMOS data taken in the GOODS north and south fields. For the first time, our NICMOS data provide imaging with sufficient angu…
Discovery of two distinct red clumps in NGC 419: a rare snapshot of a cluster at the onset of degeneracy
Girardi, Léo; Rubele, Stefano; Kerber, Leandro
Colour-magnitude diagrams (CMDs) of the Small Magellanic Cloud (SMC) star cluster NGC 419, derived from Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) data, reveal a well-delineated secondary clump located below the classical compact red clump typical of intermediate-age populations. We demonstrate that this feature belongs to the …
A systematic study of variability in a sample of ultraluminous X-ray sources
Vaughan, S.; Roberts, T. P.; Heil, L. M.
We present results from a study of short-term variability in 19 archival observations by XMM-Newton of 16 ultraluminous X-ray sources (ULXs). Eight observations (six sources) showed intrinsic variability with power spectra in the form of either a power-law or broken power-law-like continuum and in some cases quasi-periodic oscillations (QPOs). The…
A spatially resolved map of the kinematics, star formation and stellar mass assembly in a star-forming galaxy at z = 4.9
Smail, I.; Jones, T.; van Dokkum, P. +8 more
We present a detailed study of the spatially resolved kinematics, star formation and stellar mass in a highly amplified galaxy at z = 4.92 behind the lensing cluster MS1358+62. We use the observed optical, near- and mid-infrared imaging from Hubble Space Telescope ACS & NICMOS and Spitzer IRAC to derive the stellar mass and the Gemini/NIFS IFU…
Optical polarization of the Crab pulsar: precision measurements and comparison to the radio emission
Kramer, M.; Kanbach, G.; Słowikowska, A. +1 more
The linear polarization of the Crab pulsar and its close environment was derived from observations with the high-speed photopolarimeter Optical Pulsar TIMing Analyser at the 2.56-m Nordic Optical Telescope in the optical spectral range (400-750 nm). Time resolution as short as 11 µs, which corresponds to a phase interval of 1/3000 of the pul…
The structure of blue supergiant winds and the accretion in supergiant high-mass X-ray binaries
Mereghetti, S.; Sidoli, L.; Ducci, L. +2 more
We have developed a stellar wind model for OB supergiants to investigate the effects of accretion from a clumpy wind on the luminosity and variability properties of high-mass X-ray binaries. Assuming that the clumps are confined by ram pressure of the ambient gas and exploring different distributions for their mass and radii, we computed the expec…
A failed outburst of H1743-322
Belloni, T.; Capitanio, F.; Ubertini, P. +1 more
We report on a campaign of X-ray and soft γ-ray observations of the black hole candidate (BHC) H1743-322 (also named IGR J17464-3213), performed with the RXTE, INTEGRAL and Swift satellites. The source was observed during a short outburst between 2008 October 03 and November 16. The evolution of the hardness-intensity diagram throughout the outbur…
The OGLE view of microlensing towards the Magellanic Clouds - I. A trickle of events in the OGLE-II LMC data
Soszyński, I.; Udalski, A.; Szymański, M. K. +9 more
We present the results from the Optical Gravitational Lensing Experiment II (OGLE-II) survey (1996-2000) towards the Large Magellanic Cloud (LMC), which has the aim of detecting the microlensing phenomena caused by dark matter compact objects in the Galactic halo [massive compact halo objects (MACHOs)].
We use high-resolution Hubble Space Tel…