Dr. Weihua Lei (Huazhong Univ. of Science and Technology, China) visit our group and give colloquium speech

Oct 1, 2010

The central engine of gamma-ray bursts: Blandford-Znajek Process and neutrino-antineutrino annihilation”

The nature of the central engine of gamma-ray bursts (GRBs) has been one of the main puzzles of astrophysics, which is widely believed to be related to the merger of two neutron stars, the merger of neutron star and black hole, or the collapse of a supermassive star. All of these scenarios involve a rotating black hole with a hyper accretion disk or torus, from which energy is extracted for powering GRBs by neutrino-antineutrino annihilation or by extracting rotational energy from the black hole or disk via large scale magnetic field.

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Dr. Feng Yuan (SHAO) visit our group and give colloquium speech

Sep 24, 2010

“AGN Feedback at Sub-pc Scale”

The hot accretion flow is usually optically thin in the radial direction, therefore the photons produced at one radius can travel for a long distance without being absorbed. These photons can thus heat or cool electrons at other radii via Compton scattering. This effect has been ignored in most previous works.

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Dr. Bob Noble (SLAC) visit our group and give colloquium speech

Sep 10, 2010

mission is addressed in this presentation.

“Feasibility of Radioisotope Electric Propulsion for Sample Return Missions”

Fast sample return from primitive objects in the outer Solar System would open an exciting new chapter in space science, but the vast distances make this a daunting task. A sample return mission involves several complicated steps to reach an object and obtain a sample, but only the interplanetary return phase of the mission is addressed in this presentation.

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Prof. Zhang receives a NASA Fermi grant.

Aug 28, 2010

Prof. Zhang received an award from the Fermi Gamma-ray Space Telescope Cycle 3 with a total amount of $80,000. The title of his theoretical proposal is “A New Model of GRB Prompt Emission”. Zhang and collaborators propose to develop of new model of GRBs in the Poynting-flux-dominated regime, namely, the Internal Collision-induced Magnetic Reconnection and Turbulence (ICMART) model.

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Prof. Rachid Ouyed (Univ. of Calgary) visit our group and give colloquium speech

Apr 9, 2010

Astrophysical signatures of quark-matter phase transitions (the Quark-Nova)”

Supernova explosions of massive stars are generally thought to leave behind either a black hole or a neutron star. However, allowing for a quark star phase (via a Quark-Nova explosion) leads to a dual-shock phenomena (the supernova shock followed by the Quark-Nova shock) with unique astrophysical implications.

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Prof. Doug Lin (UC Santa Cruz / KIAA) visit our group and give colloquium speech

Mar 11, 2011

Origin, Structure, and Evolution of Hot Jupiters and Super-Earths”

 

In the radial-velocity and transit searches, close-in planets are the first to be found. These planets are most likely formed at much larger distances from their host stars and migrated to their present-day location.

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Prof. Yuefang Wu (Peking Univ.) visit our group and give colloquium speech

Feb 19, 2010

“Gravitational collapse in high-mass star formation region”

The high-mass star formation mechanisms remain unclear. By calculation, when a forming star reaches 8 Msun, its radiation pressure can halt spherical infall, preventing its further growth. Two major theoretical models on the further growth of such stars were suggested. One model suggested the mergence of low mass stellar objects, and the other suggested a process through accretion-disk-outflow still.

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Dr. Yosuke Mizuno (Marshall) visit our group and give colloquium speech

Feb 12, 2010

“Current-Driven Kink Instability in Relativistic Jets”

Highly-ionized fast accretion-disk winds have been suggested as an explanation for a variety of observed absorption and emission features in the X-ray spectra of Active Galactic Nuclei. Simple estimates have suggested that these flows may be massive enough to be significant for the accretion process and might even be involved in creating the link between supermassive black holes and their host galaxies.

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Prof. Davide Lazzati (NC State) visit our group and give colloquium speech

Jan 22, 2010

“Relativistic outflows, their engines, and their progenitors: a new view on what shapes Gamma-Ray Burst light curves”

Gamma-Ray Bursts are the most fascinating events in astrophysics. They are the brightest sources of radiation, they mysteriously appear and disappear in all directions, and they are seen from the largest distances and earlier epochs of the Universe. Gamma-Ray Bursts are also hard to understand and classify, owing to their extreme diversity of characteristics.

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Dr. Andrew Fruchter (STScI) visit our group and give colloquium speech

Nov 20, 2009

“Gamma-Ray Bursts from a Safe Distance”

Gamma-Ray Bursts are explosions of nearly unrivalled brilliance.  They can be bright enough to be seen at cosmological distances with the naked eye and can appear to emit the energy of the rest mass of the sun in high-energy photons in a matter of seconds.  

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