KITP
catdynamics | January 28, 2009how big is a globular cluster?
There are many ways to measure the size of a globular cluster, both observationally and theoretically.
This causes some confusion, especially when theorists try to talk to observers, or vica versa.
rc - the core radius
there are at least three definitions of this:
1) the observer definition is that this is the radius at which the surface brightness has dropped to half its central value; this assumes the surface brightness is flat at small radii and the core is resolved, otherwise the central surface brightness is underestimated by the convolution of the point…
catdynamics | January 26, 2009wherein you can learn about the "No Teleportation Theorem" and why there is no classical Scattering Theorem
or some such nonsense...
me, podcast with bonus video feed.
Argh.
one of the nice, but occasionally disturbing things about the Kavli Institute of Theoretical Physics is that they podcast and video essentially all their talks,
including
this one, with the soporifiic droning of yours truly
this is very, very disturbing...
there is also an audio podcast, not that I'd recommend having this on your iPod on long drives.
catdynamics | January 23, 2009it is still raining?!
so we have an east coaster telling us about actual data
on x-ray binaries
in clusters, globular clusters
in other galaxies...
there is an open-to-the-program-members blog over on the cluster09 wikispace.
It has some good summary of yesterdays in depth discussion on runaway mergers in the afternoon session.
Chandra image of NGC4697
so our pivot point is the issue of low mass x-ray binaries (LMXBs) - mass transfer binaries, with compact primary, generally a neutron star, and a companion with a mass lower than some vague mass that is either about a solar mass, or safely…
catdynamics | January 22, 2009it is raining, might as well liveblog the morning session...
runaway mergers of colliding stars - the quick and dirty intro...
stars are, in fact extended bodies.
This is mostly irrelevant to astronomers, since typical stellar separations are very large.
But, in dense stellar clusters, the density of stars can be a billion times higher than in the field - and hence separations thousand times smaller - and then the finite size can be really important.
Especially if stars also happen to be in binaries, but that is a different story...
So... to make a long story short, sometimes stars go "…
catdynamics | January 21, 2009Multiple stellar populations in globular clusters (overview).
like this in NGC2808 (paper)
or even good old M4, and and NGC1851, and of course Omega Cen.
the original view of globular clusters is that they are the quintessential coeval sets of stellar populations - that all the stars in any given cluster ought to have formed more or less simultaneously, with an age spread of no more than a few million years or so
but, now that we have very good colour-magnitude data from wide field Hubble images, with proper-motion selected field decontamination, it turns out that many, maybe most,…
catdynamics | January 20, 2009getting organized
- unlike the totally laid back string theorists, the astrophysics program has daily morning meetings to discuss progress
except today
today we get to meet after lunch, everybody was kinda busy this morning for some reason...
then we get informal short talk presentations once a week on thursdays, on top of the seminars, colloquia and lunch talks - the thursday talks will be recorded and podcast and video feeds made available online
ooh, first monday seminar will be:
""Emergent phenomena in negative heat capacity systems: fundamental physics from dense star clusters"
by, er…
catdynamics | January 15, 2009I am currently at the Kavli Institute for Theoretical Physics, hanging out at the "Formation and Evolution of Globular Clusters" workshop.
Apparently I am, for now, also the official "program blogger" program rapporteur...
cause you know everything sounds fancier in french
Who knew.
When David suggests something is a good idea, it becomes a good idea.
So, right now I am kinda busy trying to keep up with the workshop - there are some interesting new things, which I'll get to in due time. Real Soon Now.
Y'all can participate through the multimedia online presence, including video (live and…