SOUNDING OPEN CLUSTERS: ASTEROSEISMIC CONSTRAINTS FROM
                    <i>KEPLER</i>
                    ON THE PROPERTIES OF NGC 6791 AND NGC 6819

Basu, Sarbani; Grundahl, F.; Stello, Dennis; Kallinger, T.; Hekker, S.; Mosser, B.; García, R. A.; Mathur, S.; Brogaard, K.; Bruntt, H.; Chaplin, W. J.; Gai, Ning; Elsworth, Y.; Esch, Lisa; Ballot, J.; Bedding, Timothy R.; Gruberbauer, M.; Huber, Daniel; Miglio, A.; Yıldız, Mutlu; Kjeldsen, H.; Christensen‐Dalsgaard, J.; Gilliland, Ronald L.; Fanelli, Michael; Ibrahim, Khadeejah A.; Smith, Jeffrey C.

doi:10.1088/2041-8205/729/1/l10

Cited by 148 publications

(171 citation statements)

References 47 publications

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“…This is not a surprise as far as the four codes we are comparing employ very similar nuclear reaction rates. 8 This result supports the stringency of model-dependent age determination approaches, such as asteroseismology of red giants in clusters (Basu et al 2011;Miglio et al 2013). Figure 10 summarizes our results on the mass distribution in the α Herculis system within 1σ and 2σ uncertainties.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 77%

“…Yet, it calls for an observational calibration of surface abundances versus the global stellar parameters, such as mass and log g, which in return requires a high-precision mass assessment. The asteroseismology of oscillating red giants comes to the rescue, as it can indirectly provide measures of log g from seismic scaling laws as precise as ∼1% (see, e.g., Basu et al 2011;Morel et al 2013;Thygesen et al 2012). Once this is relaxed, surface abundance ratios might serve as an alternative technique in estimating the masses of stars when seismic and/or binarity information is missing.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

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THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Moravveji¹,

Guinan²,

Khosroshahi³

et al. 2013

200

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α 1 Her is the second closest asymptotic giant branch (AGB) star to the Sun, and the variable luminous M5 Ib-II member of a triple-stellar system containing G8 III and A9 IV-V components. However, the mass of this important star was previously uncertain, with published values ranging from ∼2-15 M . As shown by this study, its fortuitous membership in a nearby resolved triple-star system makes it possible to determine its fundamental properties including its mass and age. We present over 20 years of VRI photometry of α 1 Her as well as Wing intermediate-band near-IR TiO and NIR continuum photometry. We introduce a new photometry-based calibration technique and extract the effective temperature and luminosity of α 1 Her, in agreement with recent interferometric measures. We find average values of T eff = 3280 ± 87 K and log(L/L ) = 3.92 ± 0.14. With the MESA code, we calculate a dense grid of evolutionary tracks for Galactic low-to intermediate-mass (1.3 to 8 M ) rotating stars from the pre-main sequence phase to the advanced AGB phase. We include atomic diffusion and rotation mechanisms to treat the effects of extra elemental mixing. Based on the observed properties of the α Herculis stars, we constrain the age of the system to lie in the range 0.41 to 1.25 Gyr. Thus, the mass of α 1 Her lies in the range 2.175 M/M 3.250. We compare our model-based age inference with recent tracks of the Geneva and STAREVOL codes, and show their agreement. In the prescribed mass range for α 1 Her, the observed 12 C/ 13 C and 16 O/ 17 O ratios are consistent (within 2σ ) with the ratios predicted by the MESA, Geneva, and STAREVOL codes.

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Section: Discussion and Concluding Remarkssupporting

confidence: 77%

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Moravveji¹,

Guinan²,

Khosroshahi³

et al. 2013

200

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“…De Ridder et al 2009;Hekker et al 2009;Mosser et al 2010;Bedding et al 2010;Huber et al 2010), as well as a few hundred stars belonging to clusters (e.g. Stello et al 2010;Basu et al 2011). These data provide strong constraints on these stars.…”

Section: Introductionmentioning

confidence: 91%

Study of KIC 8561221 observed byKepler: an early red giant showing depressed dipolar modes

García

Hernández

Benomar

et al. 2014

A&A

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Context. The continuous high-precision photometric observations provided by the CoRoT and Kepler space missions have allowed us to understand the structure and dynamics of red giants better using asteroseismic techniques. A small fraction of these stars show dipole modes with unexpectedly low amplitudes. The reduction in amplitude is more pronounced for stars with a higher frequency of maximum power, ν max . Aims. In this work we want to characterise KIC 8561221 in order to confirm that it is currently the least evolved star among this peculiar subset and to discuss several hypotheses that could help explain the reduction of the dipole mode amplitudes. Methods. We used Kepler short-and long-cadence data combined with spectroscopic observations to infer the stellar structure and dynamics of KIC 8561221. We then discussed different scenarios that could contribute to reducing the dipole amplitudes, such as a fast-rotating interior or the effect of a magnetic field on the properties of the modes. We also performed a detailed study of the inertia and damping of the modes. Results. We have been able to characterise 36 oscillations modes, in particular, a few dipole modes above ν max that exhibit nearly normal amplitudes. The frequencies of all the measured modes were used to determine the overall properties and the internal structure of the star. We have inferred a surface rotation period of ∼91 days and uncovered a variation in the surface magnetic activity during the last 4 years. The analysis of the convective background did not reveal any difference compared to "normal" red giants. As expected, the internal regions of the star probed by the = 2 and 3 modes spin 4 to 8 times faster than the surface. Conclusions. With our grid of standard models we are able to properly fit the observed frequencies. Our model calculation of mode inertia and damping give no explanation for the depressed dipole modes. A fast-rotating core is also ruled out as a possible explanation. Finally, we do not have any observational evidence of a strong deep magnetic field inside the star.

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“…Beck et al 2011;Bedding et al 2011;Mosser et al 2011;Stello et al 2013;Benomar et al 2013Benomar et al , 2014 -including some belonging to a few clusters Basu et al 2011) -it is now possible to infer the core rotation rate of these stars (Beck et al 2012;Mosser et al 2012;Di Mauro et al 2013;Goupil et al 2013), which is still difficult to determine for solar-like stars and even for the Sun (e.g. García et al 2004García et al , 2007García et al , 2008a.…”

Section: Introductionmentioning

confidence: 99%

Rotation and magnetism ofKeplerpulsating solar-like stars

García

Ceillier

Salabert

et al. 2014

A&A

275

344

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Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the mainsequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.

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SOUNDING OPEN CLUSTERS: ASTEROSEISMIC CONSTRAINTS FROM KEPLER ON THE PROPERTIES OF NGC 6791 AND NGC 6819

Cited by 148 publications

References 47 publications

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Study of KIC 8561221 observed byKepler: an early red giant showing depressed dipolar modes

Rotation and magnetism ofKeplerpulsating solar-like stars

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SOUNDING OPEN CLUSTERS: ASTEROSEISMIC CONSTRAINTS FROM KEPLER ON THE PROPERTIES OF NGC 6791 AND NGC 6819

Cited by 148 publications

References 47 publications

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M☉⩽ 8.0

Study of KIC 8561221 observed byKepler: an early red giant showing depressed dipolar modes

Rotation and magnetism ofKeplerpulsating solar-like stars

Contact Info

Product

Resources

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THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0