Author Archives: gf.bertone@gmail.com

GLAST works!

The launch of the gamma-ray satellite GLAST on June 11 from Cape Canaveral, in Florida, marked the end of a 16-years long period of designing, construction and preparation, and the start of the most exciting phase: the analysis and interpretation of data. As the satellite goes through commissioning (see some event displays here) the first scientific results are flowing in.

There are big expectations for what GLAST will be able to do. In particular, the community working on extensions of the Standard Model of Particle Physics, hopes to find some hints for the existence of Weakly Interacting Massive Particles, or WIMPs, which are among the favorite candidates to explain the Dark Matter (DM).

With its unprecedented sensitivity and its very large energy range (20 MeV to more than 300 GeV) the main instrument on board the GLAST satellite, the Large Area Telescope (LAT), the LAT might in fact be able to detect an indirect DM signature for a large class of WIMP models.

Our group has studied the prospects for indirect detection of WIMP DM with a variety of different strategies, including gamma-rays and synchrotron emission from the Galactic center, DM clumps and Intermediate Mass Black Holes.

Image above: The Delta II rocket carrying the GLAST spacecraft lifts off
(NASA/Jerry Cannon, Robert Murray)

Mad About his Art

An amazing exhibit is currently on display at the Guimet Museum of Asian Arts in Paris. It is the first retrospective dedicated to Katsuhika Hokusai (1760 – 1849), indisputably among the most famous and talented Japanese painters, and a specialist in Ukiyo-e. This is what Hokusai wrote in the postscript to One Hundred Views of Mount Fuji: « Since the age of 6 years old, I have had a passion for drawing the shapes of objects. By about 50, I had published innumerable drawings, but I am dissatisfied with everythingI produced before the age of 70. It’s now, at 73 years, that I have just about understood the form and true nature of birds, fish, plants, etc. So, by the time I am 80, I will have made much progress, I will reach the bottom of things; and by 100, I will decidedly have attained a higher state, indefinable, and by the age of 110 everything – whether it be a line, or a dot – will be living. I ask those who will be alive with me then to see if I keep my word. Written at the age of 75, by me, formerly Hokusai, now Gakyo Rojin, the old man crazy about drawing.» Check out the website of the exhibit here.

Dark Matter and Stars

We don’t know what Dark Matter is. But if it is made of Weakly Interacting Massive Particles, then we know it must interact with stars.

The first time I heard about that, was back in 2000. Ilidio Lopes and Joe Silk, both at the U. of Oxford, told me about the interesting effects that WIMPs could have on the structure of the Sun. Ilidio and I included the effect of capture and annihilation of Dark Matter particles in a solar evolutionary code, but it turned out that the most interesting region of the DM parameter space did not lead to observable effects (see the paper here).

Part of the work was carried out in Lisbon, at the IST. It’s a truly fantastic city. Oh, and if you ever visit Porto, try this.

I kept thinking about DM and stars for a while, and while at FNAL I discussed a lot about this issue with John Beacom and Lam Hui. Batavia maybe is not as charming as Lisbon, but Chicago is not far, and there you might enjoy this.

Finally, Malcolm Fairbairn (who was working independently on the same ideas) and I published a paper on the effect of DM on Compact Objects such as White Dwarfs and Neutron Stars.

Recently, then, prompted by an interesting paper of I. Moskalenko and L. Wai, many groups have started working on the effect of DM on different types of stars. In particular D. Spolyar, K. Freese and P. Gondolo have shown that DM annihilations could have a dramatic impact on the evolution of Population III stars (the image above, taken from this website, shows a simulation of the formation of a Pop III star in a standard astrophysical scenario).

With the help of Georges Meynet and Sylvia Ekstrom of the Geneva Observatory, Marco Taoso (a PhD student at IAP) and I have performed a detailed analysis of the capture and annihilation of DM in Pop III stars, and have found that these stars could remain “frozen” for timescales longer than the age of the Universe. Cool, eh?

More about our results in this New Scientist article.

Welcome

Welcome to my blog. I am a researcher in the Theoretical Physics group of the Institut d’Astrophysique de Paris, and I plan to post here news about the “Dark & Otherwise” Universe, and a collection of random thoughts.