Highlights - Volume 488-2 (September III 2008)

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HIGHLIGHTS: this week in A&A

Volume 488-2 (September III 2008)


In section 10. Planets and planetary systems

“Misaligned spin-orbit in the XO-3 planetary system?”, by G. Hébrard, F. Bouchy, F. Pont, et al., A&A 488, p. 763

This is one of the first observations of a system in which the star does not appear to orbit perpendicular to the orbital plane of the planet. All other cases observed so far have their star's axis of rotation and axis of the planetary orbit perfectly aligned, within the limits of the accuracy of measurements. Here, the two axes are misaligned by ~70°. This raises many questions. Why is this system not the same as the others? Is it because the planet is massive and maybe not formed by the same mechanism? Is it just a chance effect? What does it tell us about the dynamical history of this planet, and of the others? Accurate observations of this exciting system are just beginning. A first task is to confirm that this misalignment may not be an artifact caused by the high airmass of the observations.  


In section 3. Cosmology

“COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VII. Time delays and the Hubble constant from WFI J2033-4723”, by C. Vuissoz, F. Courbin, D. Sluse, et al., A&A 488, p. 481

According to theory of general relativity, photons emitted by distant sources follow trajectories that result from the interaction with the gravitational potential of matter along their path. This phenomenon is known as "gravitational lensing" because of its intimate connection with the classical optics description. As a result, the images of such distant sources are distorted and, in some cases, split into multiple components. As the paths from different images are different, a time difference in the arrival of photons emitted at the same time is expected. Such a time delay offers one of the few available methods of obtaining an accurate measurement of the Hubble constant, H0. By using this method applied to the quadruple image of the quasar WFI J2033–4723, located at z = 1.66, the authors of this paper find an H0 value that is consistent with the presently favored concordance cosmological model. 
In section 7. Stellar structure and evolution

“NGC300 X-1 and IC10 X-1: a new breed of black hole binary?”, by R. Barnard, J.S. Clark, and U.C. Kolb, A&A 488, p. 697

These two systems are known from optical studies to have nearly the same orbital period (30 hrs), and IC10 X-1 has been identified with a WR+BH counterpart. The new results here for spectral properties and variability indicate that this is a new class of stellar mass, disk accreting, massive and hyperluminous XR binaries with black holes exceeding those often found in microquasars (e.g. SS 433). 


© Astronomy & Astrophysics 2008