Astronomy and Astrophysics-A&A Astronomy and Astrophysics-A&A, EDP Sciences, 2017, 606, ⟨10.1051/0004-6361/201730897⟩ Astronomy & astrophysics, 606:A135. EDP Sciences Astronomy & Astrophysics NASA Astrophysics Data System Astronomy and Astrophysics-A&A, 2017, 606, ⟨10.1051/0004-6361/201730897⟩