J/ApJ/838/115 Asteroseismic analysis of 8 Kepler red giants (Arentoft+, 2017)
Convective-core overshoot and suppression of oscillations: constraints from
red giants in NGC 6811.
Arentoft T., Brogaard K., Jessen-Hansen J., Silva Aguirre V., Kjeldsen H.,
Mosumgaard J.R., Sandquist E.L.
<Astrophys. J., 838, 115-115 (2017)>
=2017ApJ...838..115A 2017ApJ...838..115A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Clusters, open ; Photometry
Keywords: convection; open clusters and associations: individual (NGC 6811);
stars: evolution; stars: oscillations; techniques: photometric
Abstract:
Using data from the NASA spacecraft Kepler, we study solar-like
oscillations in red giant stars in the open cluster NGC 6811. We
determine oscillation frequencies, frequency separations, period
spacings of mixed modes, and mode visibilities for eight cluster
giants. The oscillation parameters show that these stars are
helium-core-burning red giants. The eight stars form two groups with
very different oscillation power spectra; the four stars with the
lowest Δν values display rich sets of mixed l=1 modes, while
this is not the case for the four stars with higher Δν. For
the four stars with lowest Δν, we determine the asymptotic
period spacing of the mixed modes, ΔP, which together with the
masses we derive for all eight stars suggest that they belong to the
so-called secondary clump. Based on the global oscillation parameters,
we present initial theoretical stellar modeling that indicates that we
can constrain convective-core overshoot on the main sequence and in
the helium-burning phase for these ∼2M☉ stars. Finally, our
results indicate less mode suppression than predicted by recent
theories for magnetic suppression of certain oscillation modes in red
giants.
Description:
We used Kepler long-cadence data (∼30 minutes sampling) to study eight
red giants in the open cluster NGC 6811. Each time series includes
more than 60000 data points and spans ∼1400 days (BJD 2454953-2456391,
Kepler quarters Q1-Q17; 2009 May-2013 Apr) from data release 22.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 8 Asteroseismic parameters and other properties
for the red giants in NGC 6811
table2.dat 35 326 List of frequencies for the eight stars
table3.dat 49 8 *Results from BaSTI Grid Modeling, with
uncertainties from theModel Calculations
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Note on table3.dat: We fit the observed asteroseismic and atmospheric quantities
to a grid of BaSTI (Pietrinferni+ 2004ApJ...612..168P 2004ApJ...612..168P) isochrones using the
Bayesian Stellar Algorithm (Silva Aguirre+ 2015, J/MNRAS/452/2127 and
2017, J/ApJ/835/173).
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJ/718/L97 : Early asteroseismic results from Kepler (Van Grootel+, 2010)
J/A+A/525/A131 : Solar-like oscillations in Kepler red giants (Hekker+, 2011)
J/A+A/531/A124 : Visibilities of stellar oscillation modes (Ballot+, 2011)
J/A+A/540/A143 : Oscillations of red giants observed by Kepler (Mosser+, 2012)
J/MNRAS/434/1422 : Atmospheric param. of FGKM stars (Molenda-Zakowicz+, 2013)
J/ApJ/765/L41 : Asteroseismic classification of KIC objects (Stello+, 2013)
J/ApJS/215/19 : APOKASC catalog of Kepler red giants (Pinsonneault+, 2014)
J/A+A/572/L5 : Evolution state of red giants from seismology (Mosser+, 2014)
J/MNRAS/452/2127 : Fundamental param. of Kepler stars (Silva Aguirre+, 2015)
J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)
J/A+A/588/A87 : Seismic global parameters of 6111 KIC (Vrard+, 2016)
J/ApJ/835/172 : Kepler asteroseismic LEGACY sample. I. Oscillations
(Lund+, 2017)
J/ApJ/835/173 : Kepler asteroseismic LEGACY sample. II. (Silva Aguirre+, 2017)
J/A+A/598/A62 : KIC red giants showing depressed mixed modes (Mosser+, 2017)
J/A+A/600/A1 : Coupling factors of 5166 KIC (Mosser+, 2017)
J/ApJS/229/30 : Revised properties of Q1-17 Kepler targets (Mathur+, 2017)
http://archive.stsci.edu/kepler/ : MAST Kepler home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- KIC [9409513/9776739] KIC number
9- 12 F4.2 uHz Delnu [4.8/8.6] Frequency spacing Δν
14- 17 F4.2 uHz e_Delnu Delnu uncertainty
19- 22 F4.2 uHz del02 [0.5/1] Frequency separation δ02 (1)
24- 27 F4.2 uHz e_del02 delO2 uncertainty
29- 33 F5.3 --- eps [0.8/1.1] Value of ε (1)
35- 39 F5.3 --- e_eps eps uncertainty
41- 45 F5.1 uHz numax [53/108] Frequency of maximum power νmax
47- 49 F3.1 uHz e_numax numax uncertainty
51- 53 I3 s DelPobs [100/190] Observed period spacing ΔPobs
55 I1 s e_DelPobs DelPobs uncertainty
57- 58 A2 --- l_DelP [≳] Limit flag on DelP
59- 61 I3 s DelP [125/227] Period spacing of the pure g-modes,
ΔP
63 I1 s e_DelP ? DelP uncertainty
65- 68 I4 K Teff [4826/5027] Effective temperature
70- 72 I3 K e_Teff [100] Teff uncertainty
74- 77 F4.2 Msun Mscal [2/2.4] Mass derived from scaling relations
described in Section 6
79- 82 F4.2 Msun e_Mscal Mscal uncertainty
84- 88 F5.2 Rsun Rscal [8/12.2] Radius (see Section 6)
90- 93 F4.2 Rsun e_Rscal Rscal uncertainty
95- 98 F4.2 --- logg [2.6/3] Surface gravity from the asteroseismic
parameters loggseis (1)
100-101 I2 d tau [14/29] Mode lifetime (see section 8)
103-104 I2 d e_tau tau uncertainty
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Note (1): The small frequency separation (δ02) is found from the
central l=0,2 modes; see the left panel of Figure 4. Finally the
value of ε is determined from the l=0 modes using
Equation (3). These values are listed for completeness in Table 1,
along with surface gravities determined from the asteroseismic
parameters, but are not used for the analysis in the present paper.
See section 4.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [KIC]
4- 10 I7 --- KIC Red giant KIC number in NGC6811
12- 18 F7.3 uHz Freq [33.5/145.2] Oscillation frequency
20- 24 F5.3 uHz e_Freq [0.02/0.09] Uncertainty in Freq
26- 29 F4.1 --- S/N [0.4/37] Signal-to-noise
31 I1 --- l [0/3]? l mode-identification, l-value (1)
32 A1 --- u_l Uncertainty flag on l (1)
34- 35 I2 --- n [5/17]? n mode-identification, n-value (1)
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Note (1): For oscillation modes with uncertain l-value, the corresponding
entry in the fifth data column (l) is blank. This is only relevant for
two of the stars. Other uncertain l-values are marked with ":" in the
sixth (u_l) column. For oscillation modes with l=1 (or uncertain), the
corresponding n-value in the seventh data column (n) is blank as the
modes are mixed and no n-values are therefore assigned.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- KIC [9409513/9776739] KIC number
9- 12 F4.2 Msun Mmo [2.1/2.4] BaSTI model mass
14- 17 F4.2 Msun e_Mmo [0/0.09] Negative uncertainty on Mmo
19- 22 F4.2 Msun E_Mmo [0/0.2] Positive uncertainty on Mmo
24- 28 F5.2 Rsun Rmo [8/12.3] BaSTI model radius
30- 33 F4.2 Rsun e_Rmo [0/0.2] Negative uncertainty on Rmo
35- 38 F4.2 Rsun E_Rmo [0/0.2] Positive uncertainty on Rmo
40- 43 I4 K Tmo [4886/5003] BaSTI model temperature
45- 46 I2 K e_Tmo [0/39] Negative uncertainty on Tmo
48- 49 I2 K E_Tmo [0/52] Positive uncertainty on Tmo
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Oct-2017