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Weekly Seminars for November 2008 Print E-mail

Friday 7th November 2008, 4:00 P.M.

Università "La Sapienza" Roma - Aula Conversi (Dip. Fisica, Ed. Marconi - Vecchio Edificio)

Speaker:  Prof. Piergiorgio Picozza (INFN sezione di Roma II - Dip. Fisica Università Tor Vergata) 

Title: Firts Results from the Pamela Space Experiment

Abstract: On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus is composed of a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows for precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics. Results of two years of in flight data taking are presented.

Monday 10th November 2008, 4:00 P.M.

Università "La Sapienza" Roma - Aula Conversi (Dip. Fisica, Ed. Marconi - Vecchio Edificio)

Speaker:  Dr. Luca Zampieri (INAF - Osservatorio Astronomico di Padova) 

Title: Very luminous and peculiar core-collapse supernova events: what do they tell us?

Abstract: The recent discovery of a number of very bright and peculiar supernova explosion events, such as SN 2006gy, reveals a wealth of new behaviors that appear difficult to encompass in the 'standard' evolutionary scenario of a core-collapse supernova. I will present the results and uncertainties of modelling the observed properties of these supernovae.

Wednesday 12th November 2008, 2:00 P.M.

Università "La Sapienza" Roma - Aula 6 (Dip. Fisica, Ed. Fermi - Nuovo Edificio)

Speaker:  Dr.ssa  Raffaella Margutti (Università degli studi di Milano Bicocca, Osservatorio Astronomico di Brera - INAF) 

Title: Timing Analysis of GRB afterglow and prompt light curves 

Abstract: The time variability in afterglow and prompt light curves can provide important clues to the nature of the source that powers the GRB emission and to its surroundings. We performed the first systematic search for short time scale variability in X-ray afterglow and find a minimum time scale, t_min,of variability of about 1 s. Moreover, the harder the energy channel the shorter t_min. The timing analysis of the prompt gamma-rays reveals the existence of three different classes of GRBs. A showcase for the application of this technique to the prompt gamma-ray emission is represented by the naked-eye GRB 080319B.

Wednesday 26th November 2008, 4:00 P.M.

Università "La Sapienza" Roma - Aula Amaldi (Dip. Fisica, Ed. Marconi - Vecchio Edificio)

Speaker:  Dr. Paolo D'Avanzo (Università degli studi di Milano Bicocca, Osservatorio Astronomico di Brera - INAF) 

Title: The afterglows and host galaxies of three short/hard GRBs 

Abstract: Our knowledge of short gamma-ray bursts (GRBs) has significatively improved in the Swift era. Rapid multiband observations from the largest ground-based observatories led to the discovery of the optical afterglows and host galaxies of these events. In spite of these recent advancements, the number of short GRBs with secure detections in the optical is still fairly small. Short GRBs are commonly thought to originate from the merging of double compact object binaries but direct evidence for this scenario is still missing. Optical observations of short GRBs allow us to measure redshifts, firmly identify host galaxies, characterize their properties, and accurately localize GRBs within them. Multiwavelength observations of GRB afterglows provide useful information on the emission mechanisms at work. These are all key issues that allow one to discriminate among different models of these elusive events. We present photometric observations of the short/hard GRB 051227, GRB 061006, and GRB 071227 with the ESO-VLT starting from several hours after the explosion down to the host galaxies level several days later. For GRB 061006 and GRB 071227 we also obtained spectroscopic observations of the host galaxy. For all the three above bursts, we discovered optical afterglows and firmly identified their host galaxies. About half a day after the burst, the optical afterglows of GRB 051227 and GRB 061006 present a decay significatly steeper than in the X-rays. In the case of GRB 051227, the optical decay is so steep that it likely indicates different emission mechanisms in the two wavelengths ranges. The three hosts are blue, star forming galaxies at moderate redshifts and with metallicities comparable to the Solar one. The projected offsets of the optical afterglows from their host galaxies centers span a wide range, but all afterglows lie within the light of their hosts. We discuss our findings in light of the current models of short GRB progenitors.

Thursday 27th November 2008, 3:00 P.M.

Università "La Sapienza" Roma - Aula Conversi (Dip. Fisica, Ed. Marconi - Vecchio Edificio)

Speaker:  Prof. Sergei Odintsov (Institucio Catalana de Recerca i Estudis Avancats ICREA and Institut de Ciencies de l'Espai IEEC-CSIC, Campus UAB, Facultat de Ciencies) 

Title: Inflation and dark energy from modified gravity 

Abstract: We consider several classes of modified gravities, including F(R) model, F(G) model, scalar-Gauss-Bonnet gravity and non-local gravity. Using the reconstruction scheme we show that consistent unification of early-time inflation with late-time acceleration in such models is possible. The future of the universe in such theories maybe studied too.

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