SEISMIC EVIDENCE FOR A RAPIDLY ROTATING CORE IN A LOWER-GIANT-BRANCH STAR OBSERVED WITH KEPLER

By S. Deheuvels, R. García, W. Chaplin, S. Basu, H. M. Antia, T. Appourchaux, O. Benomar, G. Davies, Y. Elsworth, Laurent Gizon and 17 more. 2012

269 citations recorded by the source corpus.

Rotation is expected to have an important influence on the structure and the evolution of stars. However, the mechanisms of angular momentum transport in stars remain theoretically uncertain and very complex to take into account in stellar models. To achieve a better understanding of these processes, we desperately need observational constraints on the internal rotation of stars, which until very recently was restricted to the Sun. In this paper, we report the detection of mixed modes—i.e., modes that behave both as g modes in the core and as p modes in the envelope—in the spectrum of the early red giant KIC 7341231, which was observed during one year with the Kepler spacecraft. By performing an analysis of the oscillation spectrum of the star, we show that its non-radial modes are clearly split by stellar rotation and we are able to determine precisely the rotational splittings of 18 modes. We then find a stellar model that reproduces very well the observed atmospheric and seismic properties of the star. We use this model to perform inversions of the internal rotation profile of the star, which enables us to show that the core of the star is rotating at least five times faster than the envelope. This will shed new light on the processes of transport of angular momentum in stars. In particular, this result can be used to place constraints on the angular momentum coupling between the core and the envelope of early red giants, which could help us discriminate between the theories that have been proposed over the last few decades.

Subfields: Astronomy and Astrophysics, Oceanography

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Citations in the corpus

REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1–16 TRANSIT DETECTION RUN (2013, background): “…AZ 85719, USA study of the core structure and rotation of subgiant and red-giant stars (Bedding et al. 2011; Beck et al. 2011; Mosser et al. 2012b; Deheuvels et al. 2012), an order of magnitude increase of known dwarf stars with detected oscillations (Chaplin et al. 2011), and the discovery of…”
ANGULAR MOMENTUM TRANSPORT WITHIN EVOLVED LOW-MASS STARS (2014, methodology): “In the era of space asteroseismology, the Kepler satellite enabled the measurement of the core rotation in many red giant branch (RGB) stars using the splitting of mixed modes (Beck et al. 2012; Deheuvels et al. 2012; Mosser et al. 2012b; Deheuvels et al. 2014).”
Asteroseismic measurement of surface-to-core rotation in a main-sequence A star, KIC 11145123 (2014, background): “2012; Deheuvels et al. 2012), and some subgiants (Deheuvelset al. 2014) and both rigid rotation (Charpinet, Fontaine & Brassard 2009) and differential rotation (Córsico et al. 2011) in two hite dwarf stars.”
Improved angular momentum evolution model for solar-like stars (2013, background): “…have so far only revealed surface rotation, except for the Sun (e.g., Turck-Chieze et al. 2011) and, more recently, for a few evolved giants (e.g., Deheuvels et al. 2012) thanks to asterosismology, the amount of angular momentum stored in the stellar interior throughout its evolution is usually…”
A new correction of stellar oscillation frequencies for near-surface effects (2014, methodology): “This scaled power-law approach has been adopted widely (e.g. Tang & Gai 2011; Mathur et al. 2012; Deheuvels et al. 2012).”
Asteroseismology of 16,000 Kepler Red Giants: Global Oscillation Parameters, Masses, and Radii (2018, background): “…et al. 2013; Mosser et al. 2015; Vrard et al. 2016; Elsworth et al. 2017; Hon et al. 2017), measurement of internal rotation (Beck et al. 2012; Deheuvels et al. 2012; Mosser et al. 2012b; Deheuvels et al. 2014) and possible detection of magnetic fields in radiative cores (Fuller et al. 2015;…”
Spin down of the core rotation in red giants (2012, background): “3), consistent with the observations reported by Beck et al. (2012) and Deheuvels et al. (2012a) for four early RGB stars.”
THE APOKASC CATALOG: AN ASTEROSEISMIC AND SPECTROSCOPIC JOINT SURVEY OF TARGETS IN THE KEPLER FIELDS (2014, background): “Rapid rotation in the cores of red giants has been discovered (Beck et al. 2012; Deheuvels et al. 2012; Mosser et al. 2012a).”
Seismic diagnostics for transport of angular momentum in stars. I. Rotational splittings from the pre-main sequence to the red-giant branch. (2012, background): “These modes mostly probe the core rotation (Beck et al. 2012; Deheuvels et al. 2012; Mosser et al. 2012a).”
Mixed modes in red giants: a window on stellar evolution (2014, background): “Determining ΔΠ1 allows us to probe the core, to monitor its rotation (Beck et al. 2012; Mosser et al. 2012a; Deheuvels et al. 2012, 2014), and to investigate how angular Article published by EDP Sciences L5, page 1 of 5 momentum is transferred between the stellar core and the envelope (Cantiello et…”
Rotation and magnetism of Kepler pulsating solar-like stars : Towards asteroseismically calibrated age-rotation relations (2014, background): “…al. 2013), but indications of the rotation profile from the external outer convection zone to the inner radiative core using inversion techniques (Deheuvels et al. 2012, 2014; Beck et al. 2014), as is also commonly done for the Sun (e.g. Thompson et al. 2003; García et al. 2008b; Mathur et al.…”
Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run (2016, background): “…data of Kepler with a large number of breakthrough discoveries, such as the asteroseismic measurement of the internal rotation (Beck et al. 2012; Deheuvels et al. 2012; Mosser et al. 2012; Deheuvels et al. 2014) and magnetic fields (Fuller et al. 2015; Stello et al. 2016) of subgiants and red…”
Asteroseismology of Solar-Type and Red-Giant Stars (2013, background): “Deheuvels et al. (2012) also recently reported the detection of rotationally split modes in HIP 92775 (KIC 7341231), a halo star at the base of the RGB.”
Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence (2015, unknown): “In particular, the detection of mixed gravity and pressure modes have allowed various groups to derive the internal rotation proﬁle of red giant stars, evolving o ﬀ the main sequence (e.g. Deheuvels et al. 2012; Mosser et al. 2012).”
Rotation periods of 12 000 main-sequence Kepler stars: Dependence on stellar spectral type and comparison with v sin i observations (2013, methodology): “Future work will include detailed starspot modeling in order to measure latitudinal differential rotation (Reinhold & Reiners 2013) and asteroseismology (e.g., Deheuvels et al. 2012) to infer internal differential rotation.”
Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler (2014, background): “For this to be true, we select only stars that do not show evidence of modes of mixed character that show greater sensitivity to the deep stellar interior (see Deheuvels et al. (2012) and Deheuvels et al. (2014) for more details on mixed modes in the context of rotation).”
PLATO as it is: a legacy mission for Galactic archaeology (2017, unknown): “…stars up to the core-He burning phase, which enables one to recover information about the internal rotational profile (e.g., see Beck et al. 2012; Deheuvels et al. 2012, 2014; Eggenberger et al. 2012; Mosser et al. 2012), or to infer the inclination of the star’s rotational axis with respect to…”