Hello everyone, A few days ago, we received the sad news that Carl Hansen passed away last week. For those of you who never met him, Carl was a very special person. He was one of the "founding fathers" of stellar seismology. I remember him from my days at Texas. He was always so enthusiastic and full of energy. I particularly remember one time he saved us by producing an FT program that took advantage of the "chunk" nature of WET data. Remember, this is back in the day when 386 desktop machines were the state of the art, and we had to use the UT Cray to do dfts of WET datasets. It would take hours to so a single dft. Carl produced an FT code that would compute a FFT of each night of observations, and then combine these chunks to produced the equivalent of a DFT, but in much less time:) I was one graduate student who was very, very grateful! Many of our codes from that time are named after him, such as shapecarl (which produces a pulse shape from data in "Carl's" format) and sumcarl, which sums data written in Carl's format. Carl was Don Winget's co-advisor at the University of Rochester. I asked him to write a bit about Carl, and he produced a beautiful tribute to Carl that he would like to share with everyone..... From Don: On the 3rd of July, 2011, we lost Carl J. Hansen. Carl was a dear friend, mentor and colleague to many of us, he influenced was and is felt across the entire field of astrophysics. I am sure no one is fully aware of all of Carl's many contributions to the fields of physics and astronomy: they were many and varied. Carl was a very humble man and never took the credit he deserved. Professionally, Carl was an excellent theoretical astrophysicist with wide and varied interests. He did pioneering work in nucleosynthesis, astro-particle physics of the production of neutrinos in stars, hydrodynamics, and stellar pulsations. He led the way in these fields with major contributions in the areas of analytical theory and in numerical simulations. He also was justifiably proud of his experimental work on laboratory constraints to our understanding of nuclear reactions in astrophysics, the perspective he gained from this work was an asset in his theoretical work in other areas. One of Carl's great scientific legacies is represented by the many codes he wrote from the 1970's and 1980's that are still being used today; many new codes have their roots in Carl's work. Carl freely gave away--"with both hands,"as Ed Nather liked to remark--these codes to his students and colleagues; in this way he was one of the scientific co-founders of the concept of open source. His major scientific legacy was as a person. His unbridled and boundless enthusiasm for life and for science quickly infected all he came into contact with. After working, or even talking, with him, you always came away excited and energized. This quality made him a one-man social network: everyone loved working with him so much that they encouraged others to do the same. This made his scientific and personal influence as broad as any scientist I have every known. You couldn't work with him without being transformed, becoming--at least a little bit--like him. This was a great thing. For this reason, Carl will always be present in each of our lives. Some personal recollections: Carl treated all people, always, with respect. He was oblivious to social hierarchy, real or imagined, in any form. He made it a point to get to know everyone he interacted with as an equal. I will never forget when I first met him in person. I was a new grad student at the University of Rochester and my thesis advisor there, Hugh Van Horn--having worked with Carl while on sabbatical at University of Colorado--recommended him to me as a co-advisor. I was elated and quickly agreed. Following tradition at the U of R, Hugh introduced Carl as "Professor Hansen." Carl simply added, with a slight air of correction, "I'm Carl." Hugh, taken slightly aback, said, "Are you sure?" To which Carl responded, "Last I checked..." I knew right away I was going to like him! I was in the final year or so of my Ph.D. work under the joint supervision of Carl and Hugh and in collaboration with Gilles Fontaine. I was very worried by the fact that a formidable figure in stellar pulsation theory, Wojtek Dziembowski, was collaborating with another leading astrophysicist, Detlev Koester, in direct competition with us to solve the problem of the excitation of pulsations in DA white dwarf stars. One day, I was particularly discouraged, sitting at my desk with my head in my hands. The phone rang. The voice on the other end said, "Beat Wojtek! Beat Wojtek! Beat Wojtek!" then the phone went dead without introduction or closing. You can guess who's voice it was on the other end of the phone. After his call I was buoyed and returned to working hard on our problem. This phone call was repeated several times during the "home stretch" of this work and the project ended in success. Carl made you feel anything was possible. This is but one of the many ways I am personally indebted to Carl for my career in astronomy. Carl was an incredibly loyal person. He was co-supervising my first graduate student, Steve Kawaler, with me when our talk turned to baseball--not surprising for either Steve or me. We asked Carl how interested he was in baseball and in what team, if any. Carl said, "Baseball died for me when the Dodgers left Brooklyn!" No more need be said. Carl and Camille were kind enough to welcome me into their home when I visited Boulder. They always made me feel comfortable. Their home was filled with the bustle of chores, until the dinner conversations wound down, usually after the dishes were done. Starting and ending each day in quiet conversation with Carl and Camille is a memory I will always treasure. It was an oasis of beauty, peace and tranquility.
