Variable stars in the field of open cluster NGC 6819 - II

Street, R. A.; Horne, K.; Lister, Tim; Penny, A. J.; Tsapras, Y.; Quirrenbach, A.; Safizadeh, N.; Cooke, Jeff; Mitchell, D.; Cameron, A. Collier

doi:10.1111/j.1365-2966.2005.08751.x

Cited by 12 publications

(6 citation statements)

References 10 publications

(12 reference statements)

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“…its movement in longitude was roughly constant over time). The approximate rotation period of this spot was assigned to the star, P = 3.4693 days, which is consistent with the value given by Street et al (2005). With the period assignment made, the reference spot will remain stationary in longitude on the surface of the star, while spots that do not remain stationary in longitude indicate possible differential rotation.…”

Section: Light-curve Inversion (Li) Methodssupporting

confidence: 81%

IMAGING STARSPOT EVOLUTION ONKEPLERTARGET KIC 5110407 USING LIGHT-CURVE INVERSION

Roettenbacher¹,

Monnier²,

Harmon³

et al. 2013

ApJ

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The Kepler target KIC 5110407, a K-type star, shows strong quasi-periodic light curve fluctuations likely arising from the formation and decay of spots on the stellar surface rotating with a period of 3.4693 days. Using an established light-curve inversion algorithm, we study the evolution of the surface features based on Kepler space telescope light curves over a period of two years (with a gap of .25 years). At virtually all epochs, we detect at least one large spot group on the surface causing a 1-10% flux modulation in the Kepler passband. By identifying and tracking spot groups over a range of inferred latitudes, we measured the surface differential rotation to be much smaller than that found for the Sun. We also searched for a correlation between the seventeen stellar flares that occurred during our observations and the orientation of the dominant surface spot at the time of each flare. No statistically-significant correlation was found except perhaps for the very brightest flares, suggesting most flares are associated with regions devoid of spots or spots too small to be clearly discerned using our reconstruction technique. While we may see hints of long-term changes in the spot characteristics and flare statistics within our current dataset, a longer baseline of observation will be needed to detect the existence of a magnetic cycle in KIC 5110407.

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Section: Light-curve Inversion (Li) Methodssupporting

confidence: 81%

IMAGING STARSPOT EVOLUTION ONKEPLERTARGET KIC 5110407 USING LIGHT-CURVE INVERSION

Roettenbacher¹,

Monnier²,

Harmon³

et al. 2013

ApJ

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show abstract

“…Finally, we note that NGC 6819 and another Kepler cluster, NGC 6791, contain detached eclipsing binaries (Talamantes & Sandquist 2009;Street et al 2005;de Marchi et al 2007;Mochejska et al 2005). For these stars masses and radii can be determined independently (Grundahl et al 2008), which will further strengthen results of asteroseismic analyses.…”

Section: Asteroseismic "Color-magnitude Diagrams"supporting

confidence: 66%

DETECTION OF SOLAR-LIKE OSCILLATIONS FROM KEPLER PHOTOMETRY OF THE OPEN CLUSTER NGC 6819

Stello

Basu

Bruntt

et al. 2010

ApJ

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Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819 -one of four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation, ∆ν, and the frequency of maximum oscillation power, ν max . We find that the asteroseismic parameters allow us to test cluster-membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about two orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler.

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“…V2 in their list) included in the photometry of our study. Street et al (2002Street et al ( , 2005 also detected a number of eclipsing binaries from a much wider cluster field (∼ 11 ′ ×22 ′ ). They confined their search to variable stars This figure shows that many BSS candidates exhibit a moderate variablity (1.0 < I W S < 2.0).…”

Section: Variable Blue Stragglersmentioning

confidence: 94%

Wiyn Open Cluster Study Ii: Wide-Field CCD Photometry of the Old Open Cluster NGC 6819

Yang

Sarajedini

Deliyannis

et al. 2012

ApJ

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We present a comprehensive photometric study of the old open cluster, NGC 6819 using 1 • ×1 • field V I MOSAIC CCD imaging taken with the WIYN 0.9m telescope. The resultant color-magnitude diagram (CMD) shows a well developed main sequence (MS) extending from V ∼14.5 mag down to our photometric limit of V ∼21 mag. Fitting theoretical isochrones with adopted values of the reddening and metallicity (E(B − V ) =0.14, [F e/H] = +0.09 dex) to the observed CMD yields a distance modulus of (m − M ) 0 =11.93±0.10 and an age of ∼ 2.6 Gyr for NGC 6819. Our wide-field imaging reveals that NGC 6819 is larger in areal extent (R =13 ′ ) than previously thought. The wide-field also benefits our estimate of the degree of field star contamination, and ultimately yields improved measurements of the structural parameters (r c =2.80 ′ , r t =38.2 ′ , and r h =7 ′ ) and tidal mass of the cluster (M tid =3542.4 M ⊙ ). The flattened luminosity and mass functions indicate that NGC 6819 has experienced mass segregation as a result of its dynamical evolution. Our variability study of the cluster blue straggler star (BSS) population using the Welch-Stetson variability index (I W S ) has revealed a number of variable BSS candidates.

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Variable stars in the field of open cluster NGC 6819 - II

Cited by 12 publications

References 10 publications

IMAGING STARSPOT EVOLUTION ONKEPLERTARGET KIC 5110407 USING LIGHT-CURVE INVERSION

IMAGING STARSPOT EVOLUTION ONKEPLERTARGET KIC 5110407 USING LIGHT-CURVE INVERSION

DETECTION OF SOLAR-LIKE OSCILLATIONS FROM KEPLER PHOTOMETRY OF THE OPEN CLUSTER NGC 6819

Wiyn Open Cluster Study Ii: Wide-Field CCD Photometry of the Old Open Cluster NGC 6819

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