Dr. Berry Holl

I was the opponent today in the PhD defense of Berry Holl (Lund). As opponent, my role was to draw out the content of the thesis with questions and also subject the candidate to (extremely public) scientific scrutiny. It was great fun, in part because the thesis was so good, and in part because Holl handled the questions so well and so completely. His thesis has a lot of challenging linear algebra in its core (and I love linear algebra) but in the end I found myself spending most of my time on the 2/7 of his thesis that dealt with radiation damage to the Gaia CCDs. The question Holl answered is what that damage is likely to do to the data and to the precise measurement (and more importantly modeling) of the transit times of the stars. The conclusion we came to during the event is that the Gaia science data will actually contain more information about charge-transfer inefficiency and radiation damage than any other source of data before or during the mission. And that includes all the data that have been taken expressly for the purpose of learning about radiation damage!

Many Gaia projects have this character: The nasty systematic effect (general relativity in the Solar System, substellar companions, surface convection on giants) that matter at Gaia precision turn Gaia into the world's most sensitive measuring device for those effects. So in particular, at the end of the Gaia mission, we will have a great deal of precise quantitative knowledge about the behavior of CCDs that have been damaged; a great deal of precise knowledge about CCDs in general, really.

Holl passed his defense unanimously, of course, and it is with this post that I congratulate him and welcome him to the community of scholars!