title: Deviations from a uniform period spacing of gravity modes in a massive star.
abstract: The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution. The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly problematic for massive stars. Oscillations in stars with masses a few times that of the Sun offer a unique opportunity to disentangle the nature of various mixing processes, through the distinct signature they leave on period spacings in the gravity mode spectrum. Here we report the detection of numerous gravity modes in a young star with a mass of about seven solar masses. The mean period spacing allows us to estimate the extent of the convective core, and the clear periodic deviation from the mean constrains the location of the chemical transition zone to be at about 10 per cent of the radius and rules out a clear-cut profile.
authors.affiliation: Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium. pieter.degroote@ster.kuleuven.ac.be
authors.forename: Pieter
authors.initials: P
authors.lastname: Degroote
authors.forename: Conny
authors.initials: C
authors.lastname: Aerts
authors.forename: Annie
authors.initials: A
authors.lastname: Baglin
authors.forename: Andrea
authors.initials: A
authors.lastname: Miglio
authors.forename: Maryline
authors.initials: M
authors.lastname: Briquet
authors.forename: Arlette
authors.initials: A
authors.lastname: Noels
authors.forename: Ewa
authors.initials: E
authors.lastname: Niemczura
authors.forename: Josefina
authors.initials: J
authors.lastname: Montalban
authors.forename: Steven
authors.initials: S
authors.lastname: Bloemen
authors.forename: Raquel
authors.initials: R
authors.lastname: Oreiro
authors.forename: Maja
authors.initials: M
authors.lastname: Vucković
authors.forename: Kristof
authors.initials: K
authors.lastname: Smolders
authors.forename: Michel
authors.initials: M
authors.lastname: Auvergne
authors.forename: Frederic
authors.initials: F
authors.lastname: Baudin
authors.forename: Claude
authors.initials: C
authors.lastname: Catala
authors.forename: Eric
authors.initials: E
authors.lastname: Michel