Monthly Notices of the Royal Astronomical Society: Letters Monthly Notices of the Royal Astronomical Society: Letters, 2016, 461 (2), pp.1404. ⟨10.1093/mnras/stw1258⟩ Monthly Notices of the Royal Astronomical Society: Letters, Oxford Journals, 2016, 461 (2), pp.1404. ⟨10.1093/mnras/stw1258⟩