DOUBLE STARS

Author: BALASTEGUI MANSO ANDREU.
Year: 2005.
University: BARCELONA [www.ub.es].
Place of defense: FACULTAD DE FÍSICA.
Place of preparation: UNIVERSIDAD DE BARCELONA.

Summary: The gamma-ray bursts (English gamma-ray bursts, or GRBs for short) have been classified traditionally GRBs short and hard, and GRBs long and soft, according to the distribution biomodal their lifetimes. This classification is proposing a border, T90 = 2 s, to separate GRBs shorts long. Indeed, the distributions of GRBs short durations and should have a long interval durations where they overlap, and the classic classification is unable to classify GRBs in this region. This thesis proposes a new classification of GRBs. Using multiple variables inherent to GRBs and using automatic classification algorithms own artificial intelligence, such as cluster analysis and neural networks, it is a classification of GRBs with the objective that we can discriminate against what class every GRB even belongs in the region of overlap in the distribution of lengths. Furthermore, these algorithms suggest the existence of 3 classes of GRBs different. Introducing therefore, two classifications of GRBs, one of two classes (2-Iy 2-II) and other three classes (3-I, 3-II and 3-III). The classification into two classes recovers characteristics of the classification classic GRBs, while ranking in three classes proposes a new class of GRBs long term and soft. In this classification the GRBs class 3-III have as a main feature of the changing brightness with the redshift. These are GRBs the ideal candidates to come from the collapse of very massive stars through the phenomenon known as "collapsing. Moreover, GRBs class 3-Iy 3-II occur at distances smaller than average class 3-III being ideal candidates to come from the merger of double compact systems. The second part of the thesis is devoted to the identification of parameters of GRBs as extragalactic are his pace explosion role and function of redshift of light. The measure is done by adjusting the distribution of intensities of GRBs, also known as the diagram log N-log P. This thesis has been parameterized pace with exploding GRBs and their luminosity function with greater freedom than other jobs, and have been adjusted both. Results are presented for each of the classes GBRs reported in the first part of the thesis. Because the GRBs class 3-III come from the collapse of massive stars exploded his rhythm is proportional to the rate of stellar formation. By the pace of explosion of GRBs class 3-III deduce that the history of stellar formation in the Universe began as a sudden and a very high pace, with what is known as an outburst of stellar formation. By adjusting the distribution of intensities of GRBs are also determining the parameters cosmological omegaM and omega ^. Shown here also the competitiveness of the method used in relation to other recently (the type of supernovae, CMB and X-ray clusters). Finally, it presents a series of simulations which show a great potential for improvement in the accuracy of the method when the number of GRBs known an order of magnitude.