Host: Dong Lai

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Abstract:

The vast majority of the pulsar wind nebulae (PWNe) present in the Galaxy are middle-aged systems that have gone already, or are about to go through a strong interaction of the PWN itself with the supernova remnant (SNR), a process referred to as reverberation. Modelling these systems can be quite complex and numerically expensive, due to the non-linearity of the PWN-SNR evolution even in the simple one-dimensional (1D)/one-zone case. In radiation models in fact, the details of such reverberation are either ignored, or, in a few cases, described in simplified ways. I will present some of the results of an effort to understand reverberation of PWNe in detail. In particular, I will discuss the validity of some of the usual assumptions taken, e.g., how thin is the PWN boundary or how constant (or Sedov like) is the pressure outside the PWN. I will also introduce a new numerical technique that couples the numerical efficiency of the one-zone thin shell approach with the reliability of a full 'Lagrangian' evolution that is able to correctly reproduce the PWN-SNR interaction during the reverberation and to consistently evolve the particle spectrum beyond. Our approach enables us for the first time to provide reliable spectral models of the later compression phases in the evolution of PWNe. While in general, we found that the compression is less extreme than that obtained without such detailed dynamical considerations, leading to the formation of less structured spectral energy distributions, we find that a non-negligible fraction of PWNe will experience a strong super-efficient phase, with the optical and/or X-ray luminosity exceeding the spin-down power of the pulsar at the time.

Biography:

I am an ICREA Professor of Astrophysics based at the Institute of Space Sciences. I was born in Buenos Aires, Argentina. I studied there up to obtaining my doctoral degree in physics from the National University at La Plata, working on cosmology and astrophysics of extended gravitational theories. After several fellowships (Astronomy Centre of Sussex University in UK, Institute for Radioastronomy in Argentina, Princeton University and the Lawrence Livermore Laboratory in the USA) and some stays in Italy (International Center for Theoretical Physics at Trieste, Salerno University at Baronissi), I moved to Barcelona right at the end of 2005 to work at the Institute of Space Sciences and start a research group on high-energy astrophysics.