Are inner disc misalignments common? ALMA reveals an isotropic outer disc inclination distribution for young dipper stars. Issue 1 (2nd December 2019)

• Record Type: Journal Article
• Authors: Ansdell, M; Gaidos, E; Hedges, C; Tazzari, M; Kraus, A L; Wyatt, M C; Kennedy, G M; Williams, J P; Mann, A W; Angelo, I; Dûchene, G; Mamajek, E E; Carpenter, J; Esplin, T L; Rizzuto, A C
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 492:Issue 1(2020)
• Page Start: 572
• Page End: 588
• Publication Date: 2019-12-02
• Subjects: planet–star interactions -- protoplanetary discs -- binaries: visual -- stars: variables: T Tauri, Herbig Ae/Be; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz3361
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of per cent. A standard explanation is that dippers host nearly edge-on ( i d ≈ 70°) protoplanetary discs that allow close-in (<1 au) dust lifted slightly out of the mid-plane to partially occult the star. The identification of a face-on dipper disc and growing evidence of inner disc misalignments brings this scenario into question. Thus, we uniformly (re)derive the inclinations of 24 dipper discs resolved with (sub-)mm interferometry from ALMA. We find that dipper disc inclinations are consistent with an isotropic distribution over i d ≈ 0−75°, above which the occurrence rate declines (likely an observational selection effect due to optically thick disc mid-planes blocking their host stars). These findings indicate that the dipper phenomenon is unrelated to the outer (>10 au) disc resolved by ALMA and that inner disc misalignments may be common during the protoplanetary phase. More than one mechanism may contribute to the dipper phenomenon, including accretion-driven warps and 'broken' discs caused by inclined (sub-)stellar or planetary companions.