Numerical Methods for Radiative and Ideal Relativistic Hydrodynamics Applied to the Study of Gamma-Ray Bursts

Numerical methods for radiative and ideal relativistic hydrodynamics applied to the study of gamma-ray bursts Julio David Melon Fuksman Department of Physics University of Rome “La Sapienza” This dissertation is submitted for the degree of Doctor of Philosophy IRAP PhD program Supervisor: Dr. Carlo L. Bianco September 2019 A Julio y Elena Acknowledgements I am obliged to express my gratitude towards a number of people who have helped me in different ways throughout the last three and a half years, making this work possible. First of all, I would like to thank the organizers of the IRAP PhD Program for the financial support throughout the time of my PhD. I also thank my advisor, Carlo L. Bianco, and Professors Jorge A. Rueda and Gregory V. Vereshchagin for their guidance and the many fruitful discussions we had. I thank the entire staff of Sapienza and ICRANet, in particular Cinzia Di Niccolo, Federica Di Berardino, Cristina Adamo, Silvia Latorre, Gabriele A. Brandolini, and Elisabetta Natale, for being so helpful and kind to me ever since my arrival in Pescara. I would like to thank all of the members of the Thesis Comittee and the external evaluators for aiding me in the final stage of my PhD by taking the time to read this thesis and express their judgement. Among the scientists I have met since I arrived in Italy, I must especially mention Andrea Mignone. I am indebted to you for welcoming my interest to work together and consistently trusting it would lead to a good place. Above all, however, I thank you deeply for your support in the last year, and for always finding some time to talk when I needed advice. You arean example to follow both as a scientist and as a person. I would also like to thank all of the students of the ICRANet group I have met in these years, starting with Daria Primorac and Andreas Krut. We have shared so many adventures, some of them rather extreme, and we survived them all. I treasure the amazing experiences we lived together and the times we have stood up for each other. As well, I thank José Fernando Rodríguez Ruiz and Margarita Velandia Avendaño for their continued support and friendship. You are amazing people and many moments throughout this PhD were made easier thanks to you. I must also mention Rahim Moradi and Yu Wang, who welcomed me into the group in Pescara, as well as Marco Muccino and Giovanni Pisani, who did the same in Rome. I thank Yerlan Aimuratov, Laura Becerra, Stefano Campion, Diego Cáceres Uribe, Gabriel Guimarães Carvalho, Vahagn Harutyunyan, Mile Karlica, Miloš Kovačević, Iarley Pereira Lobo, Clément Stahl, Juan David Uribe Suárez, and Ronaldo Vieira Lobato for the great moments we shared. Lastly, I thank Rafael Ignacio Yunis for the mates and his (always very Argentinian) words of encouragement. During my years at Sapienza I have met several people outside of my group that have brought countless cheerful moments into the day-by-day experience of my PhD, starting with vi the students of Stanza 117. In particular, I want to thank José Manuel Ruiz Franco for his daily Maradonian encouragement in the worst and best moments of the PhD. No me alcanzan todos los alfajores del planeta para agradecerte lo que me has bancado estos años. Gracias por tantos cafés compartidos (que casi nunca me has dejado pagar), por los partidos de fútbol, las birras, y las juntadas en tu casa. Mil gracias también a Carmen por estas últimas. I must also thank Nicolás García for being so welcoming to me when I first arrived to the Physics Department, and for bringing me to the RCAI. I thank my irmão Jorge Henrique Nogueira for his support, and for the many great moments and trips we shared. In this sense, I also thank Gabriela Navarro, Nazanin Davari, and Francesco De Santis. A great deal of my stress during these years was relieved thanks to the football group I helped organize together with Matt Starr, Jan Delshad, and Alan Daventry. I thank the three of you for your amazing friendship and for building such a wonderful community that has brought together so many people who, like us, were far from home. Agradezco de corazón a mis amigos de toda la vida, esos que son mi familia y me lo hacen sentir cada vez que vuelvo a la Argentina, en particular a Ana Ailén Armanelli, Daniela Giraldez, Ramiro Manuel Monzón Herrera, Nicolás Gabriel Ojea, Lisandro Parodi, y Matías Pérez Rojas, por bancarme y quererme, literalmente, siempre. Agradezco a Cintia Buonzerio por los mismos motivos y por algunos otros que los dos sabemos. Agradezco también a Lucas Javier Albornoz, Nahuel Almeira, Rodrigo Bonazzola, Ignacio Ferreiro, Paloma Machain y Nicolás Vattuone, los integrantes de La Casa. Pese a estar desperdigados por el mundo, nos hemos acompañado a la distancia, y las veces que he podido verlos, ya sea en Argentina o en algún lugar del norte, hemos vuelto a esa fantástica atmósfera que creamos juntos en Bariloche. Agradezco también a Octavio Cabrera Morrone por confiar en mis capacidades y sacarme de la vorágine del doctorado para divertirnos un poco y pensar juntos otro tipo de problemas. I am deeply indebted to Courtney Ann Pereira for her incredible support, especially in moments when I could do nothing but work day and night. You consistently brought happiness and tranquility into my mind in the darkest days. You are an amazing person, and this work was largely possible thanks to you. Finalmente agradezco a mi familia, en particular a mis padres, Elena Margarita Fuksman y Julio César Melon. Gracias por bancarse todos estos años lejos de casa, y por venir a visitarme cada vez que han podido. A ustedes debo no solo su eterno cariño y apoyo, sino también mi curiosidad y mis eternas ganas de aprender más sobre el mundo. En definitiva, ustedes son el motor de todo. Agradezco por último el cariño de mi abuela, Olga Anunciada Pirro, que siempre entendió que estuviera acá y me acompañó desde donde pudo, sin saber bien qué estaba haciendo yo del otro lado del mar. Abstract This thesis is devoted to the application of high-resolution numerical methods for relativistic hydrodynamics (RHD) to the study of gamma-ray bursts (GRBs), as well as to the development of new schemes able to describe radiative transfer in relativistic magnetized and unmagnetized flows. On one side, we have performed RHD simulations of relativistic plasma outbursts within the binary-driven hypernova model, developed throughout the last years in the International Center of Relativistic Astrophysics Network (ICRANet1). This model is based on the so- called induced gravitational collapse scenario, proposed to explain the observed temporal coincidence of GRBs and supernovae (SN) of type Ic. This scenario considers a carbon-oxigen star (COcore) forming a tight binary system with a companion neutron star (NS). When the collapse of the COcore produces a type Ic SN, part of the ejected material is accreted by the NS, which in turn collapses and forms a black hole (BH). It has been proposed, although the details of this process are a matter of current research, that this collapse creates an optically thick electron-positron plasma around the BH that expands due to its own internal pressure and originates a GRB. Our work in this context has focused on the description of such expanding plasma and its interaction with the surrounding SN ejecta, for which we have followed a hydrodynamical approach using the open-source code PLUTO. This allowed us to study this process in high-density regions that had not been explored thus far, and to perform consistency checks of the model taking into account both theoretical and observational constraints such as the system’s size, the initial plasma energy, the observed timing and the Lorentz factor of the outbursts. Three different scenarios are here considered: (I) the expansion of the plasmain low-density regions, proposed to produce most of the GRB emission in the prompt phase; (II) a model in which X-ray flares are produced due to the breakout of shocks created whenthe plasma interacts with high-density regions of the SN ejecta; and (III) a model for the emission of secondary bursts due to the creation of reflected waves caused by the same interaction. The second part of this thesis is devoted to the main part of our work, which consists in the development of a numerical code for radiative transfer integrated in PLUTO. Our implementation is able to solve the equations of relativistic radiation magnetohydrodynamics (Rad-RMHD) under the so-called M1 closure, which allows the radiation transport to be handled in both the free-streaming and diffusion limits. Since we use frequency-averaged opacities, this approach is unable to describe frequency-dependent phenomena; instead, 1https://www.icranet.org/ viii the main focus is put on the transport of total energy and momentum. To avoid numerical instabilities arising due to the possibly large timescale disparity caused by the radiation– matter interaction terms, the Rad-RMHD equations are integrated following implicit–explicit (IMEX) schemes. In this way, interaction terms are integrated implicitly, whereas transport and all of the remaining source terms are solved explicitly by means of the same Godunov- type solvers included in PLUTO. Among these, we have introduced a new Harten–Lax–van Leer–contact (HLLC) solver for optically thin radiation transport. The code is suitable for multidimensional computations in Cartesian, spherical, and cylindrical coordinates using either a single processor or parallel architectures. Adaptive grid computations are also made possible by means of the CHOMBO library.

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