The accelerating rotation of the magnetic He-weak star HD 142990. Issue 4 (16th May 2019)

• Record Type: Journal Article
• Authors: Shultz, M; Rivinius, Th; Das, B; Wade, G A; Chandra, P
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 486:Issue 4(2019)
• Page Start: 5558
• Page End: 5566
• Publication Date: 2019-05-16
• Subjects: stars: early-type -- stars: individual: HD142990 -- stars: magnetic fields -- stars: massive -- stars: rotation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz1129
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: HD 142990 (V 913 Sco; B5 V) is a He-weak star with a strong surface magnetic field and a short rotation period ( P rot ∼ 1 d). Whilst it is clearly a rapid rotator, recent determinations of P rot are in formal disagreement. In this paper, we collect magnetic and photometric data with a combined 40-yr baseline in order to re-evaluate P rot and examine its stability. Both period analysis of individual data sets and O − C analysis of the photometric data demonstrate that P rot has decreased over the past 30 yr, violating expectations from magnetospheric braking models, but consistent with behaviour reported for 2 other hot, rapidly rotating magnetic stars, CU Vir and HD 37776. The available magnetic and photometric time series for HD 142990 can be coherently phased assuming a spin-up rate$\dot{P}$ of approximately −0.6 s yr −1, although there is some indication that$\dot{P}$ may have slowed in recent years, possibly indicating an irregular or cyclic rotational evolution.