J/AJ/151/66 Velocities of WOCS 24009 and WOCS 40007 in NGC 6819 (Brewer+, 2016)
Determining the age of the Kepler open cluster NGC 6819 with a new triple system
and other eclipsing binary stars.
Brewer L.N., Sandquist E.L., Mathieu R.D., Milliman K., Geller A.M.,
Jeffries M.W.JR, Orosz J.A., Brogaard K., Platais I., Bruntt H.,
Grundahl F., Stello D., Frandsen S.
<Astron. J., 151, 66 (2016)>
=2016AJ....151...66B 2016AJ....151...66B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Binaries, eclipsing ; Spectroscopy ;
Radial velocities
Keywords: binaries: eclipsing - binaries: spectroscopic -
open clusters and associations: individual (NGC 6819) -
stars: evolution - techniques: photometric - techniques: spectroscopic
Abstract:
As part of our study of the old (∼2.5Gyr) open cluster NGC 6819 in the
Kepler field, we present photometric (Kepler and ground-based
BVRCIC) and spectroscopic observations of the detached eclipsing
binary WOCS 24009 (Auner 665; KIC5023948) with a short orbital period
of 3.6 days. WOCS 24009 is a triple-lined system, and we verify that
the brightest star is physically orbiting the eclipsing binary using
radial velocities and eclipse timing variations. The eclipsing binary
components have masses MB=1.090±0.010M☉ and
MC=1.075±0.013M☉, and radii
RB=1.099±0.006±0.005R☉and
RC=1.069±0.006±0.013R☉. The bright non-eclipsing star
resides at the cluster turnoff, and ultimately its mass will directly
constrain the turnoff mass: our preliminary determination is
MA=1.251±0.057M☉. A careful examination of the light curves
indicates that the fainter star in the eclipsing binary undergoes a
very brief period of total eclipse, which enables us to precisely
decompose the light of the three stars and place them in the
color-magnitude diagram (CMD). We also present improved analysis of
two previously discussed detached eclipsing stars in NGC6819
(WOCS40007 and WOCS23009) en route to a combined determination of the
cluster's distance modulus (m-M)V=12.38±0.04. Because this paper
significantly increases the number of measured stars in the cluster,
we can better constrain the age of the CMD to be
2.21±0.10±0.20Gyr. Additionally, using all measured eclipsing
binary star masses and radii, we constrain the age to
2.38±0.05±0.22Gyr. The quoted uncertainties are estimates of
measurement and systematic uncertainties (due to model physics
differences and metal content), respectively.
Description:
Radial velocities were obtained using spectra from the high-precision
survey of NGC 6819 (Hole et al. 2009, cat. J/AJ/138/159; Milliman et
al. 2014, cat. J/AJ/148/38). These spectroscopic data were taken as
part of the WOCS (Mathieu 2000ASPC..198..517M 2000ASPC..198..517M) using the WIYN13 3.5m
telescope on Kitt Peak and Hydra Multi-Object Spectrograph instrument
(MOS), which is a fiber-fed spectrograph capable of obtaining about 80
spectra simultaneously (∼10 fibers set aside for sky measurements and
∼70 for stellar spectra). Observations used the echelle grating with a
spectral resolution ∼15km/s. Most of the spectra were centered at
513nm with a 25nm range covering an array of narrow absorption lines
around the Mgb triplet. Of the 41 spectra we had available, 34 covered
wavelengths between 5000 and 5240Å, roughly centered on the Mgb
triplet, 6 covered 5460-5730Å, and one covered 6233-6227Å.
Table2 presents the measured radial velocities for WOCS24009 and
WOCS40007.
The eclipse timings are given in Table4 with the earliest eclipse
observed from the ground in 2001 July (Talamantes et al.
2010AJ....140.1268T 2010AJ....140.1268T).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 57 80 Measured radial velocities from the WIYN 3.5m
telescope
table3.dat 101 7 Measured parameters for stars in NGC6819
table4.dat 53 1262 Eclipse timings
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See also:
J/AJ/149/121 : WOCS. LXV. Abundances in NGC 6819 (Lee-Brown+, 2015)
J/AJ/148/51 : WOCS. LXI. NGC 6819 photometry (Anthony-Twarog+, 2014)
J/AJ/148/38 : WOCS. LX. RV survey of NGC 6819 (Milliman+, 2014)
J/AJ/146/58 : Eclipse timings for NGC 6819-259 (Jeffries+, 2013)
J/AJ/146/43 : WOCS. LV. NGC 6819 (Platais+, 2013)
J/ApJ/729/L10 : KIC stars properties in NGC 6791 and NGC 6819 (Basu+, 2011)
J/AJ/138/159 : NGC 6819 stellar radial-velocity and photometry (Hole+, 2009)
J/MNRAS/358/795 : Variable stars in NGC 6819 field (Street+, 2005)
J/AJ/121/327 : Metal Abundances of Red Clump Stars in NGC6819
(Bragaglia+, 2001)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [WOCS]
6- 10 I5 --- WOCS [24009/40007] WIYN Open Cluster Study number
(24009 or 40007)
12- 20 F9.4 d MJD Modified Julian Date of observation
22- 27 F6.2 km/s RVA [-84.7/95.2] Radial velocity of A component
29- 32 F4.2 km/s e_RVA [0.02/1.8] Uncertainty in RVA
34- 40 F7.2 km/s RVB [-101.5/109.3]? Radial velocity of B component
42- 45 F4.2 km/s e_RVB [0.02/4.9]? Uncertainty in RVB
47- 52 F6.2 km/s RVC [-91.5/88.7]? Radial velocity of C component
54- 57 F4.2 km/s e_RVC [0.3/9.5]? Uncertainty in RVC
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [WOCS]
6- 10 I5 --- WOCS [23009/40007] WIYN Open Cluster Study number
(23009, 24009, or 40007)
12 A1 --- m_WOCS [A-C] Component (A, B, or C)
14- 19 F6.3 mag Vmag [15.1/17] The V band magnitude (1)
21- 25 F5.3 mag B-V [0.58/0.75] The B-V color index (1)
27- 30 I4 K Teff [5855/6350]? Effective temperature
32- 36 F5.3 --- M/Msun [1/1.5]? The stellar mass to Sun mass ratio
(M/M☉)
38- 42 F5.3 --- e_M/Msun [0.007/0.06]? Error in M/M☉
44 A1 --- f_M/Msun [b] Flag "b" indicates M/M☉ is based on a
photometry-based extrapolation from other
eclipsing stars in the cluster
46- 50 F5.3 --- R/Rsun [1/2.2]? The stellar radius to Sun radius ratio
(R/R☉)
52- 56 F5.3 --- e_R/Rsun [0.002/0.009]? Error in R/R☉
58- 62 F5.3 --- err [0.005/0.013]? Second error in R/R☉
64 A1 --- f_err [c] Flag on the two uncertainties (2)
66- 70 F5.2 mag DM [12.3/12.4]? The cluster's distance modulus
(m-M)v
72- 75 F4.2 mag e_DM [0.07/0.08]? Error in DM
77- 89 F13.8 d Per [3/8333]? Period (from Table5)
91-101 F11.8 d e_Per [0/30]? Error in Per (from Table5)
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Note (1): The quoted photometry is from Kalirai et al. (2001AJ....122..266K 2001AJ....122..266K),
but has not been corrected for zeropoint differences in calibration or for
differential reddening.
Note (2): c=the two uncertainties are estimates of the random and systematic
effects with the systematic uncertainty estimated from the scatter in the
three models in Table6.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [WOCS]
6- 10 I5 --- WOCS [24009/40007] WIYN Open Cluster Study number
(24009 or 40007)
12- 24 F13.5 d BJD Barycentric Julian Date
26- 32 F7.5 d e_BJD The 1σ uncertainty in BJD
34 A1 --- Type [PS] Eclipse type (P=primary or S=secondary)
36- 53 A18 --- Note Timing source note ("-Q#" indicates the
beginning of Kepler Q#)
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History:
From electronic version of the journal
(End) Prepared by [AAA]; Sylvain Guehenneux [CDS] 21-Jul-2016