Search Publications
LBQS 0103-2753: A Binary Quasar in a Major Merger
Junkkarinen, V.; Shields, G. A.; Chapman, S. C. +3 more
We present Hubble Space Telescope (HST) and United Kingdom Infrared Telescope spectra and images of the 2 kpc (0farcs3) binary quasar LBQS 0103-2753 (z = 0.858). The HST images (V and I bands) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation alon…
Detection of Accretion X-Rays from QS Vir: Cataclysmic or a Lot of Hot Air?
Drake, Jeremy J.; Steeghs, Danny; Kashyap, Vinay +1 more
An XMM-Newton observation of the nearby "pre-cataclysmic" short-period (P orb = 3.62 hr) binary QS Vir (EC 13471-1258) revealed regular narrow X-ray eclipses when the white dwarf passed behind its M2-4 dwarf companion. The X-ray emission provides a clear signature of mass transfer and accretion onto the white dwarf. The low-resolution X…
Soft Coronal X-Rays from β Pictoris
Schmitt, J. H. M. M.; Robrade, J.; Günther, H. M. +3 more
A-type stars are expected to be X-ray dark, yet weak emission has been detected from several objects in this class. We present new Chandra/HRC-I observations of the A5 V star β Pictoris. It is clearly detected with a flux of (9 ± 2) × 10-4 counts s-1. In comparison with previous data this constrains the emission mechanism and…
Scattering of the f-mode by Small Magnetic Flux Elements from Observations and Numerical Simulations
Felipe, T.; Braun, D.; Crouch, A. +1 more
The scattering of f-modes by magnetic tubes is analyzed using three-dimensional numerical simulations. An f-mode wave packet is propagated through a solar atmosphere embedded with three different flux tube models that differ in radius and total magnetic flux. A quiet-Sun simulation without a tube present is also performed as a reference. Waves are…
Global Modeling of X-Ray Spectra Produced in O-type Star Winds
Nazé, Y.; Rauw, G.; Hervé, A. +1 more
High-resolution X-ray spectra of O-type stars revealed less wind absorption than expected from smooth winds with conventional mass-loss rates. Various solutions have been proposed, including porous winds, optically thick clumps, or an overall reduction of the mass-loss rates. The latter has a strong impact on the evolution of the star. Our final g…
An Empirical Measure of the Rate of White Dwarf Cooling in 47 Tucanae
Tremblay, P. -E.; Stetson, P. B.; Bergeron, P. +8 more
We present an empirical determination of the white dwarf cooling sequence in the globular cluster 47 Tucanae. Using spectral models, we determine temperatures for 887 objects from Wide Field Camera 3 data, as well as 292 objects from data taken with the Advanced Camera for Surveys. We make the assumption that the rate of white dwarf formation in t…
First Observation in the South of Titan's Far-infrared 220 cm-1 Cloud
Teanby, N. A.; Calcutt, S. B.; de Kok, R. +15 more
An emission feature at 220 cm-1 which has been attributed to a cloud of condensed material in Titan's winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm-1, as yet unidentifi…
The S4G Perspective on Circumstellar Dust Extinction of Asymptotic Giant Branch Stars in M100
Holwerda, Benne; Ho, Luis C.; Meidt, Sharon E. +19 more
We examine the effect of circumstellar dust extinction on the near-IR (NIR) contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17 AGB-dominated clusters we extract optical-to-mid-IR spectral energy distributions (SEDs) and find that NIR brightness is coupled to the mid-IR…
Dynamical Mass Constraints on the Ultraluminous X-Ray Source NGC 1313 X-2
Orosz, Jerome; Bregman, Joel N.; Liu, Jifeng
Dynamical mass measurements hold the key to answering whether ultraluminous X-ray sources (ULXs) are intermediate-mass black holes (IMBHs) or stellar-mass black holes with special radiation mechanisms. NGC 1313 X-2 is so far the only ULX with Hubble Space Telescope light curves, the orbital period, and the black hole's radial velocity amplitude ba…
The First Confirmed Microlens in a Globular Cluster
Minniti, D.; Udalski, A.; Pietrukowicz, P. +2 more
In 2000 July/August a microlensing event occurred at a distance of 2.33 arcmin from the center of the globular cluster M22 (NGC 6656), observed against the dense stellar field of the Milky Way bulge. We have used the adaptive optics system NACO at the ESO Very Large Telescope to resolve the two objects that participated in the event: the lens and …