Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 476, Issue 1, Pages 1234-1241Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty308
Keywords
asteroseismology - techniques; photometric - techniques; spectroscopic - stars; massive - stars; oscillations - stars; rotation
Categories
Funding
- Fund for Scientific Research of Flanders (FWO), Belgium
- Research Council of KULeuven, Belgium
- Fonds National de la Recherche Scientific (F.R.S.-FNRS), Belgium
- Royal Observatory of Belgium
- Observatoire de Geneve, Switzerland
- Thuringer Landessternwarte Tautenburg, Germany
- European Research Council (ERC) under the European Union's Horizon research and innovation programme [670519]
- Spanish Ministry of Economy and Competitiveness (MINECO) [AYA2010-21697-C05-04, AYA2012-39364-C02-01]
- Severo Ochoa [SEV-2011-0187]
- MINECO-programme 'Juan de la Cierva Incorporacion' [IJCI-2015-26034]
- Australian Research Council's [DE140101364]
- National Aeronautics and Space Administration [NNX14AB92G]
- NASA Office of Space Science [NNX09AF08G]
- NASA Science Mission
- STFC [ST/N000919/1, ST/K00106X/1] Funding Source: UKRI
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We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of f(rot) = 0.0373 d(-1) and its harmonics. This dominant frequency corresponds with a rotation period of 26.8 d and is subject to amplitude and phase modulation. The K2 photometry additionally reveals multiperiodic low-frequency variability (< 1.5 d(-1)) and is in full agreement with low-cadence high-resolution spectroscopy assembled during 1800 d. The spectroscopy reveals rotational modulation by a dynamic aspherical wind with an amplitude of about 20 km s(-1) in the H alpha line, as well as photospheric velocity variations of a few kms(-1) at frequencies in the range 0.2-0.6 d(-1) in the Si III 4567 angstrom line. Given the large macroturbulence needed to explain the spectral line broadening of the star, we interpret the detected photospheric velocity as due to travelling superinertial low-degree large-scale gravity waves with dominant tangential amplitudes and discuss why. Leo is an excellent target to study how the observed photospheric variability propagates into the wind.
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