Tag Archives: astrophysics

The Lithium problem. Primordial, cosmological or stellar?

We all have heard about it since kindergarden, but would you bet 5000 SEK you know exactly what it is? I did not, so had to look it up. And here is what I have learned.
First of all, let’s play it fair: there’s two stable lithium isotopes, lithium-six and lithium-seven. In the last years it seemed both had problems, but we are talking about the bigger brother here, the one who has had problems for a longer time. Since 1982, 30 years ago -when my brother was born- there have been observations of lithium-seven in metal poor stars of the galactic halo.

Dissipative photospheres in gamma-ray bursts

One of the many research topics at OKC is the study of gamma-ray bursts (GRBs). Several aspects of them are studied, such as the gamma-ray and X-ray emission, the afterglow emission, and the interaction between the bursts and the circumburst medium.

In a recent paper based on observations with the Fermi Gamma-ray Space Telescope it is argued that the main emission during the first few minutes of GRBs is dominated by the jet photosphere and that there is significant amount of energy dissipation close to the photosphere. This result is significant for our understanding of physics of GRB jets.