J/ApJ/900/154 Mount Wilson S-Index of 94 Aqr A and 94 Aqr B (Metcalfe+, 2020)
The evolution of rotation and magnetic activity in 94 Aqr Aa from
asteroseismology with TESS.
Metcalfe T.S., van Saders J.L., Basu S., Buzasi D., Chaplin W.J.,
Egeland R., Garcia R.A., Gaulme P., Huber D., Reinhold T., Schunker H.,
Stassun K.G., Appourchaux T., Ball W.H., Bedding T.R., Deheuvels S.,
Gonzalez-Cuesta L., Handberg R., Jimenez A., Kjeldsen H., Li T., Lund M.N.,
Mathur S., Mosser B., Nielsen M.B., Noll A., Celik Orhan Z., Ortel S.,
Santos A.R.G., Yildiz M., Baliunas S., Soon W.
<Astrophys. J., 900, 154 (2020)>
=2020ApJ...900..154M 2020ApJ...900..154M
ADC_Keywords: Stars, double and multiple; Asteroseismology
Keywords: Stellar activity ; Stellar evolution ; Stellar oscillations ;
Stellar rotation
Abstract:
Most previous efforts to calibrate how rotation and magnetic activity
depend on stellar age and mass have relied on observations of
clusters, where isochrones from stellar evolution models are used to
determine the properties of the ensemble. Asteroseismology employs
similar models to measure the properties of an individual star by
matching its normal modes of oscillation, yielding the stellar age and
mass with high precision. We use 27 days of photometry from the
Transiting Exoplanet Survey Satellite to characterize solar-like
oscillations in the G8 subgiant of the 94 Aqr triple system. The
resulting stellar properties, when combined with a reanalysis of 35yr
of activity measurements from the Mount Wilson HK project, allow us to
probe the evolution of rotation and magnetic activity in the system.
The asteroseismic age of the subgiant agrees with a stellar isochrone
fit, but the rotation period is much shorter than expected from
standard models of angular momentum evolution. We conclude that
weakened magnetic braking may be needed to reproduce the stellar
properties, and that evolved subgiants in the hydrogen shell-burning
phase can reinvigorate large-scale dynamo action and briefly sustain
magnetic activity cycles before ascending the red giant branch.
Description:
We use observations from the Mount Wilson Observatory (MWO) HK project
(Vaughan+ 1978PASP...90..267V 1978PASP...90..267V ; Wilson 1978ApJ...226..379W 1978ApJ...226..379W &
Baliunas+ 1995ApJ...438..269B 1995ApJ...438..269B) to study the long- and short-term
variability of magnetic activity in 94 Aqr A and B. The HK Project
HKP-1 (1966-1978) and HKP-2 (1978-2003) spectrophotometers obtained
counts through 1Å triangular bandpasses centered on the CaII H & K
line cores at 3968.470Å and 3933.664Å, respectively, as well as
two 20Å pseudo-continuum bands, R centered at 4001.067Å, and V
centered at 3901.068Å. See Section 2.1.
TESS observed 94 Aqr in 2 minute cadence for 27 days during Sector 2
of Cycle 1 (2018 August 22-September 20). See Section 2.2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
23 19 06.73 -13 27 31.6 * 94 Aqr A = HD 219834A
23 19 06.56 -13 27 18.9 * 94 Aqr B = HD 219834B
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 26 3687 Long-term variability of 94 Aqr A and 94 Aqr B
from the Mount Wilson S-index data
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See also:
B/wds : The Washington Visual Double Star Catalog (Mason+ 2001-2020)
I/276 : Tycho Double Star Catalogue (TDSC) (Fabricius+ 2002)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/ApJ/457/L99 : 25yr CaII-HK observations of F-K nearby stars (Baliunas+, 1996)
J/AJ/132/161 : NStars project: The southern sample. I. (Gray+, 2006)
J/AJ/145/41 : Radial velocities of 33 spectroscopic binaries (Katoh+, 2013)
J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)
J/A+A/572/A34 : Pulsating solar-like stars in Kepler (Garcia+, 2014)
J/A+A/572/L5 : Evolution state of red giants from seismology (Mosser+, 2014)
J/A+A/573/A89 : STAGGER-grid of 3D stellar models. III. (Magic+, 2015)
J/A+A/580/A23 : Stroemgren-Crawford uvbyβ photometry cat. (Paunzen, 2015)
J/AJ/150/50 : Speckle interferometry at SOAR in 2014 (Tokovinin+, 2015)
J/ApJ/831/L6 : Eclipsing binary parallaxes with Gaia data (Stassun+, 2016)
J/A+A/601/A67 : Kepler solar-type stars modeling (Creevey+, 2017)
J/ApJ/835/25 : Calibrated solar S-index time series (Egeland+, 2017)
J/ApJS/233/23 : APOKASC catalog of KIC dwarfs and subgiants (Serenelli+, 2017)
J/AJ/153/136 : Planets and their host stars with Gaia plx (Stassun+, 2017)
J/ApJ/858/28 : Mixing-length parameter for a sample of KIC (Viani+, 2018)
J/ApJS/241/12 : The Asteroseismic Target List (ATL) for TESS (Schofield+, 2019)
J/ApJ/888/43 : APOGEE-Kepler Cool Dwarf star ages (Claytor+, 2020)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- ID Identifier ("219834A" or "219834B")
9- 19 F11.5 d JD Julian Date; JD-2440000
21- 26 F6.4 --- S-Index [0.135/0.36] S-Index value
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History:
From electronic version of the journal
(End) Prepared by [AAS), Emmanuelle Perret [CDS] 03-Jan-2022