Sept 22

"Yet Another Parallax of the Hyades, and Why You Should Care"
Fritz Benedict, Secretary, American Astronomical Society

In 1997 the HST Astrometry Science Team published parallaxes of seven members of the Hyades cluster. These disagreed to a significant degree with Hipparcos. In the intervening years we have (1) improved our basic calibrations, (2) improved the data reduction pipeline, and (3) improved our methodology. Also, for a few golden weeks in late 2008 - early 2009, HST was all astrometry all the time. We exploited this situation and obtained some newer Hyades data. We use our improved analyses and these newer data to answer: 'Did Hipparcos get it right back then?' Has the re-analysis of HST data improved the comparison? All this and coming astrometric attractions.

Oct 6

"The Square Kilometre Array"
Steve Rawlings, Oxford University, UK

The SKA represents the future of radio astronomy. I will review the key science drivers for the phased roll-out of the project, focussing on observations of the history of Hydrogen from the dark ages to the present day and tests of fundamental physics with pulsars and surveys of perhaps a billion galaxies.

Nov 3

"Close Binaries in Globular Clusters: The Keys to Dynamical Evolution"
Dave Pooley, University of Texas at Austin

Globular clusters and X-ray astronomy have a long and fruitful history. The earliest rockets and satellites revealed a population of highly luminous X-ray sources in globular clusters, and later satellites revealed a larger population of low luminosity X-ray sources. It was realized early on that the high luminosity sources were low-mass X-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the Galaxy. However, the low luminosity sources proved difficult to classify. Many ideas were put forth, but secure identifications were scarce before the launch of Chandra. To date, Chandra has observed over 80 Galactic globular clusters, and these observations have revealed over 1500 X-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogenous mix, all of which are close binary systems or their offspring. These are the kinds of sources that provide the internal energy to stabilize a globular cluster against collapse. I will show that the number of X-ray sources in a globular cluster correlates very well with its encounter frequency, which points to dynamical formation scenarios for the X-ray sources and shows them to be excellent tracers of the complicated internal dynamics of globular clusters. I will also discuss how the relation between the encounter frequency and the number of X-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters.