astro
catdynamics | April 21, 2009Two Earth Mass Planet found in close orbit around a red dwarf star
Gliese 581 is an M3 red dwarf, it has a mass of about a third that of the Sun, slightly lower metal content and is about the same age probably a bit older than the Sun, we think.
It is about 20 light years away.
Gliese 581 was known to have three planets already:
Gl 581b - 1/20th of Jupiter mass in a 5 day orbit == ok, 16 Earth masses
Gl 581c - 1/60th of Jupiter mass in a 13 day orbit == 5 Earth masses
Gl 581d - 1/50th of Jupiter mass in 67 day eccentric orbit == 7 Earth masses
Now there is Gl 581e, discovered with high…
catdynamics | April 13, 2009on that last good friday nine astronomers gathered for the last time for the dreaded 11 am rapid fire discussion session in the Founder's Room at the Kavli Institute
there were six degenerate faculty types
two post-AGB hot stars headed for the cooling sequence of the tenure track
and one lone sub-giant, fresh off the graduate main sequence...
we chatted a bit about Pismis 24
it is a very nice cluster
then, just as we were about to pack it up and go to lunch early,
Glenn brought up SN
again
ok, he had an idea,
ok, it was kinda an interesting idea,
ok, so some of us couldn't resist asking…
catdynamics | April 9, 2009So what did I learn...
Flying fish make great "rationality tokens"
Multiple Populations are probably real and a problem.
I owe Bob, Jay, Chris and others an apology, they've been saying this for decades...
Intermediate Mass Black Holes are Important and Interesting.
But, we need to calm down a little bit about them.
We don't understand as much as we used to.
Δ Y?
Really?
Maybe.
Interesting...
Somebody Really Really Really needs to go and compile a HST level quality, homogenous catalog of globular cluster parameters etc
Existing catalogs rely too much on heterogenous, largely pre-CCD…
catdynamics | April 9, 2009the Kavli Institute program on Dynamics and Evolution of Globular Clusters is reaching the end, and we highlight the important issues...
The west is the best
The west is the best
Get here, and we'll do the rest
Key topics:
Stellar Content
Present Day Mass Functions, M/L
Intermediate Mass Black Holes
Blue Stragglers
Binary Fraction
Planets
Multiple Populations: not just Δ Y
Funny IMF or Funny dynamics.
AGB or rapidly rotating high mass stars?
LMXBs, BHs, CVs
Structure
Milky Way Catalog
Models: King, Wilson etc
Surface Brightness Profile
Core Collapse, Post-Core Collapse…
catdynamics | April 8, 2009final stretch and we contemplate big stellar clusters in small galaxies
in particular, if you plot the observed number of globular clusters as a function of galaxy magnitude you find the specific incidence, the number of globulars per unit light, is high for large ellipticals and small for Milky Way like spirals, but there is some evidence the specific incidence if also high for low luminosity dwarf galaxies
or is it...?
Fornax dSph from NS at Uppsala
Paul "finally I know how to pronounce his last name" Goudfrooji tutors us on globular clusters in late type dwarf galaxies
ADS link
Is the…
catdynamics | April 7, 2009last week of the globs workshop, so the pace is stepped up, with two talks this afternoon
Michele on dynamical evolution (video and podcast)
32k runs, parametric over initial conditions
evolved mass function, primordial binaries, tidal field, variable initial concentration, IMBH presence
Glenn on dynamical Schwarzschild modeling (video and podcast)
Schwarzschild orbit models
First intro to state of the art for fitting galaxy models
using Sauron integral field spectroscopy plus photometry
and get h3 and h4 of course (gaussian weighted skew and kurtosis for you heathens)
Nice models
then…
catdynamics | April 7, 2009back from a brief but complex zig zag across the Southland
and we are getting ready to wrap up the globs workshop
if only we could find someone to organise the final thursday dinner...
what all happened:
yesterday Tom did a recap of the 5th UC Irvine Center for Cosmology workshop: Intermediate-Mass Black Holes: from First Light to Galactic Nuclei which had a large number of very exciting and topical talks by top researchers.
Top researchers I tell you.
Before that there were talks on open clusters:
Jarrod - video and podcast and
Aaron - video and podcast
Today Douglas tutors us on N-…
catdynamics | April 2, 2009Bob!
We move on to open clusters, in the hope that we may actually understand those, since they are smaller and more tractable for simulations, right?
Right...
Open Clusters
"All you have to do is just go look..."
NGC 3293
Typical densities - few per cubic parsec
velocity dispersion ~ km/sec
core radius ~ 1 pc
tidal radius ~ 10-20 pc
half mass relaxation time ~ 100 Myrs - ages from zero to several Gyrs
metallicities - -0.4 < [Fe/H] < +0.3
But what about NGC 6791 - old massive and metal rich... globular or open?
click to embiggen
NGC 6791
ok, so what we really need is a sensible…
catdynamics | April 1, 2009a second year grad student doing his first observing run somewhere in Europe is reporting a naked eye supernova in the galactic plane in the Sagittarius constellation
twitter feeds from somewhere across the Atlantic say
"wow, it is really bright, and I know it can't be Venus"
01.04.09:
Early indications suggest the presence of Hα and OIII lines, and there are indications that the emission is highly variable.
One message suggested evidence for periodicity, or at least quasi-periodic oscillations, possibly indicating prompt formation of a slow pulsar.
There are clear anecdotal indications of…
catdynamics | March 31, 2009This beautiful tuesday morning, Dave tutors us on relaxation and cluster core collapse.
Then it is party at Alison's place.
But, first, we go through thermodynamics of self-gravitating internally relaxed systems, multiple equilibria and general dimensionless solutions.
Open Cluster M7 (from Utahskies.org)
Globular cluster M4 (from Utahskies.org)
Core collapsed? Or not?
Globular cluster M15 (from Utahskies.org - ok actually hubblesite, but they had a scaled copy and I was on a roll)
Definitely core collapse, we think.
Seriously - there are more core collapsed or post-core collapsed…
catdynamics | March 30, 2009Questa confusione non mi piace!
Parli piu silenziosamente, per favore.
Seriamente, ho mal di testa.
Si, si, pero avete considerato i campi magnetici?
Fermate, per favore.
Personalmenta, credo che il cafe espresso e disgustoso!
The Clusters09 Guide to Defusing Italian Discussions in the Morning Session (pdf)
For some strange reasons, the above list of romanic pseudo-code appeared on a KITP blackboard a couple of weeks ago.
I think it appeared when we were discussing Y and multiple populations...
Fortuitously, the list was preserved for posterity, so that future generations may have productive…
catdynamics | March 30, 2009The dynamics workshop in back, refreshed and ready to rock with yet more people in place.
This morning Melvyn tutors us on planets.
In globular clusters.
Planets in globulars clusters?!
From the CfA wallpaper collection - very nice images btw
Well, yes, maybe.
Or, more generally planets in very dense stellar associations.
Dynamically planets tend to get stripped quickly if they are orbiting at more than a few AU in a typical cluster.
But, planets closer in can stick around for gigayears, and those tend to be the ones we can observe.
We looked...
we found something interesting elsewhere...…
catdynamics | March 26, 2009intense and dense afternoon as we get the current state of the art about neutron star natal kicks, theory and observational constraints
Chevy supernova!
Vicky - on NS-NS constraints (video and podcast)
need >~ 2.1-2.3 solar mass He cores to get to iron and classic type II SNe
stable mass transfer may lower this limit
electron capture supernovae, in binaries, may limit on core masses right before SNe town to ~ 1.45 solar masses or more
evidence other than presence in globulars for subpopulation of neutron stars having low kick speeds: high mass x-ray binaries with e < 0.2 and…
catdynamics | March 26, 2009Phil tutors us today on neutron star formation and retention in globulars.
So we expect neutron stars to be made in globular clusters.
Massive metal poor stars should undergo supernovae and make neutron stars for a mass range of ~ 8-15-or-20 solar masses, maybe more or less, and depending a little bit on whether they are in a tight binary.
More massive stars may, or may not, make stellar mass black holes. But we are not here to talk about black holes, at least not this part of this morning.
So, when type II supernovae go bang (and we're not totally sure yet of the details of how that works,…
catdynamics | March 25, 2009Tom leads today, talking some more about Intermediate Mass Black Holes and possible evidence for black holes in globulars.
NGC 4472 in x-rays
ok, so there is probably a black hole in a globular in NGC 4472, and this, and the discovery paper
and very nice it is too
variable point x-ray source (well, XMM detection...) in a globular
at about 20 times Eddington luminousity, for a neutron star, in a high state
seen a transition to factor 7 lower state, mostly due to deficit of sub keV component, indicative of local foreground absorption
interesting... someone give them some XMM and/or Chandra…
catdynamics | March 24, 2009you'd think that clusters that are bigger ought to be more massive, and vica versa.
ah, but are they? Arunav discusses
cf figure 2 in Kissler-Patig et al 2006
which was by all accounts a most invigorating and energetic discussion
but I missed 95% of it, as my paymasters required my presence in another realm
for the afternoon's entertainment
Andreas (video and podcast) discusses modeling of tidal tails, specifically Pal 5
Pal 5
and
Mario (video and podcast) discusses the ongoing hunt for evidence for IMBHs in galactic globulars
NGC 2298
yup, that NGC 2298
catdynamics | March 23, 2009Astrophysicists like to quantify their estimates. One way to do that is to offer bets, with odds, on hypotheses or models being correct. There have been some famous bets, with spectacular odds.
We now have a new one, and a very daring one too.
Prof. Cole Miller gave today's Director's Blackboard talk:
Black Holes in Dense Star Clusters (video and podcast)
The main focus of the talk are the much speculated about "Intermediate Mass Black Holes" - black holes too massive to have descended from single stars, but not really the "Supermassive Black Holes" found in the centers of (most) galaxies.…
catdynamics | March 23, 2009Carnival of Space #95 at Orbital Hub.
Actually an interesting assortment of posts this week.
catdynamics | March 23, 2009the sun is back, and so is the intrepid gang of globularists here at the Kavli institute
apparently this week is gravitational radiation sources, with primary focus on intermediate mass black holes - including evidence hinting at their possible presence, and the possible fun things we can do with them
blackboard lunch today is on IMBHs, and will be webcast in due course as will an unusually high proportion of this weeks talks
PS: Cole left up a handy dandy gravitational radiation tutorial (pdf)