Our friend and colleague Hugo Schwarz died tragically in a motorbike accident in La Serena, Chile, on October 20, 2006. In collaboration with the Nordic Optical Telescope of La Palma, where Hugo has acted as the Astronomer in Charge from 1995 to 2000, we want to dedicate APN4 to his memory.
Hugo was well known by most of us, not only for his top quality scientific works but also for his wonderful, warm personality. He had an extraordinary character: just give a look at the weblog that has been setup in his memory to realise it.
Scientifically, Hugo has been a very active astronomer in the field of PNe and symbiotic stars since the end of the 80's, when he discovered the Southern Crab, a magnificent nebula around the symbiotic Mira Hen 2-104 (Schwarz Aspin & Lutz 1989). Since that time, he has been a source of endless ideas about the possible evolutionary paths in the crucial transition from giant stars to PNe and white dwarfs. A major contribution of Hugo was his extensive image catalog of PNe (Schwarz, Corradi & Melnick 1992) - still the largest one available - which contributed to making the issue of the shaping of PNe one of the most debated and fashionable aspects of the research in the field. Setting strong observational links between the most extreme bipolar geometries in PNe and the most massive population of progenitors was the next achievement (Stanghellini, Schwarz & Corradi 1993, Corradi & Schwarz 1995, Schwarz & Corradi 1995 in APN1).
His fine studies of a number individual objects, like the fascinating Butterfly Nebula M2-9 (Schwarz et al. 1997), led Hugo to defend with even more enthusiasm some of his ideas about the importance of evolution in binary system - in particular interactions with compact stellar companions and the formation of accretion discs and their precession - in the shaping of PNe. These are still some of the key concepts that we will be discussing in APN4.
More recently, he had started an ambitious programme of 3-D photoionization modeling of an extensive sample of PNe, with the main aim of contributing to the solution of the long-standing problem of the PNe distance determinations (e.g. Schwarz & Monteiro 2006).
In all conferences that Hugo has attended, he has always contributed a lot to both science and atmosphere. His scientific and public talks, and his private conversations were infused with humor and wonder. Among many other things, we will never forget his tremendously entertaining "toast" at the conference banquet for the 1992 "Mass Loss on the AGB and Beyond" meeting that he organized in La Serena, and the excellent conference summary he gave at APN II. We will miss him a lot.