1. I.
Physikalisches Institut, Universität zu Köln, Zülpicher
Straβe 77, 50937 Köln, Germany,
2. Harvard−Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, United States
3. School
of Engineering and Applied Sciences, Harvard University, 29 Oxford
Street, Cambridge, Massachusetts 02138, United States
4. Centro
de Astronomia e Astrofísica, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
5. Dipartimento
di Chimica ‘G. Ciamician’ Università di Bologna, Via F. Selmi 2, 40126 Bologna, Italy