Outstanding Thesis Awarded to Francisco Javier Virgili

Apr 18, 2008
Outstanding Thesis

The 2008 recipient for the Outstanding Thesis Award in the College of Sciences is Francisco Javier Virgili. His thesis, entitled, “Monte Carlo Analysis of the Luminosity Function of Gamma Ray Bursts,” applies the Monte Carlo simulation technique to constrain gamma-ray burst (GRB) luminosity function (number of GRBs as a function their luminosities) using a set of observational criteria. In particular, he focused on the possibility that low-luminosity GRBs might form a distinct new component. This is a theoretical investigation with the application of observational data.

GRBs are short blasts of gamma-rays from a given location in the sky whose origin is still mysterious. These bursts are observed in equal numbers from every direction in the sky, suggesting they originate outside the Milky Way galaxy. Astronomers think GRBs are caused by massive collapsing stars, or mergers between very heavy objects such as black holes and neutron stars.

In nominating Virgili, his advisor, assistant professor of physics and astronomy Bing Zhang, noted “In early 2006, some observations by NASA’s Swift satellite raised the possibility that low-luminosity GRBs are probably more common. Our group wrote a paper to suggest the two-component luminosity function for long GRBs. This paper (Liang, Zhang, Virgili & Dai, 2007, The Astrophysical Journal, 662, 1111- 1118) was published in June 20, 2007, and has been widely cited by the GRB community. According to the NASA ADS archives, the paper already had 32 citations as of Feb. 22, 2008. Francisco contributed to this publication as the third author. His role was to independently check the results of the leading authors through his Monte Carlo simulations. Later Francisco further developed his code and used a full set of observational criteria (including the 1-dimensional and 2-dimensional distributions of GRB redshifts and luminosities, as well as the peak flux distribution of the detected GRBs by both Swift and an earlier mission BATSE) to test a list of models that have been discussed in the literature (including the two-component model luminosity function model proposed by our group). He drew the conclusion that all the previous one-component models have the difficulty to reproduce at least one observational constraints. He then drew the firm conclusion that the two-component luminosity function model is demanded by the data. This work has been submitted to Monthly Notices of Royal Astronomical Society for publication, and Francisco is the first author of the paper.”

No student submitted his or her dissertation for the 2008 Outstanding Dissertation Award, thus no recipient was selected.

Leave a Reply

You must be logged in to post a comment.