J/AJ/149/121 WOCS. LXV. Abundances in NGC 6819 (Lee-Brown+, 2015)
Spectroscopic abundances in the open cluster NGC 6819.
Lee-Brown D.B., Anthony-Twarog B.J., Deliyannis C.P., Rich E., Twarog B.A.
<Astron. J., 149, 121 (2015)>
=2015AJ....149..121L 2015AJ....149..121L
ADC_Keywords: Clusters, open ; Effective temperatures ; Rotational velocities ;
Radial velocities ; Abundances
Keywords: open clusters and associations: individual: NGC 6819 -
stars: abundances
Abstract:
High-dispersion spectra of 333 stars in the open cluster NGC 6819,
obtained using the HYDRA spectrograph on the WIYN 3.5m telescope, have
been analyzed to determine the abundances of iron and other metals
from lines in the 400Å region surrounding the Li6708Å line. Our
spectra, with signal-to-noise per pixel ranging from 60 to 300, span
the luminosity range from the tip of the red giant branch to a point
two magnitudes below the top of the cluster turnoff. We derive radial
and rotational velocities for all stars, as well as [Fe/H] based on 17
iron lines, [Ca/H], [Si/H], and [Ni/H] in the 247 most probable,
single members of the cluster. Input Teff estimates for model
atmosphere analysis are provided by (B-V) colors merged from several
sources, with individual reddening corrections applied to each star
relative to a cluster mean of E(B-V)=0.16. Extensive use is made of
ROBOSPECT, an automatic equivalent width measurement program; its
effectiveness on large spectroscopic samples is discussed. From the
sample of likely single members, [Fe/H]=-0.03±0.06, where the error
describes the median absolute deviation about the sample median value,
leading to internal precision for the cluster below 0.01dex. The final
uncertainty in the cluster abundance is therefore dominated by
external systematics due to the temperature scale, surface gravity,
and microturbulent velocity, leading to [Fe/H]=-0.02±0.02 for a
sub-sample restricted to main sequence and turnoff stars. This result
is consistent with our recent intermediate-band photometric
determination of a slightly subsolar abundance for this cluster.
[Ca/Fe], [Si/Fe], and [Ni/Fe] are determined to be solar within the
uncertainties. NGC 6819 has an abundance distribution typical of solar
metallicity thin disk stars in the solar neighborhood.
Description:
Spectroscopic data were obtained for target stars in NGC 6819 using
the WIYN 3.5m telescope and HYDRA multi-object spectrograph over 13
nights from 2010 September and October, 2011 June, and 2013 February.
Our spectra cover a wavelength range ∼400Å wide centered on
6650Å, with dispersion of 0.2Å/pixel. Examination of
Thorium-Argon lamp spectra indicates that the line resolution
comprises 2.5 pixels, yielding a spectral resolution over 13000.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 333 Stellar parameters for the NGC 6819 sample
table3.dat 43 333 Abundances for individual stars in the NGC 6819
sample
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See also:
J/AJ/148/38 : WIYN open cluster study. LX. RV in NGC 6819 (Milliman+, 2014)
J/AJ/146/43 : WIYN open cluster study. 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 NGC 6819
(Bragaglia+, 2001)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- WOCS [1002/80025] WIYN Open Cluster Study number
7- 12 I6 --- P13 ?=0 Platais et al. 2013 (cat. J/AJ/146/43) number
14- 15 I2 --- Mm [0/99]? Cluster membership probability
17- 21 F5.3 mag B-V The (B-V) color index
23- 27 F5.3 mag E(B-V) The E(B-V) reddening estimate
29 I1 --- Np [1/4] Number of photometric sources
31- 34 I4 K Teff [3797/7319] Effective temperature
36- 39 F4.2 [cm/s2] logg [1.09/4.37] Log surface gravity
41- 44 F4.2 km/s Vt [0.85/2.57] Microturbulent velocity
46- 48 I3 --- S/N [18/369] Signal-to-Noise per pixel
50- 53 F4.1 km/s vsini [4.1/32.2] Rotational velocity
55- 57 F3.1 km/s e_vsini [0.1/7.1] 1σ uncertainty in vsini
59- 63 F5.1 km/s RV [-16.2/35.4] Radial velocity
65- 67 F3.1 km/s e_RV [0.5/4.4] 1σ uncertainty in RV
69- 71 A3 --- SB1 Indicates a single-lined spectroscopic binary
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- WOCS [1002/80025] WIYN Open Cluster Study number
7- 11 F5.2 [Sun] [Fe/H] [-0.75/0.32] Median log of the Fe/H abundance
13- 16 F4.2 [Sun] MAD [0.02/1.04] Median Absolute Deviation (MAD)
statistics for each [Fe/H] estimate (1)
18- 19 I2 --- o_[Fe/H] [3/32] Number of iron lines
21- 25 F5.2 [Sun] [Ca/H] [-2/0.6]? Log of the Ca/H abundance
27- 31 F5.2 [Sun] [Si/H] [-0.5/0.52]? Log of the Si/H abundance
33- 37 F5.2 [Sun] [Ni/H] [-1.6/1]? Log of the Ni/H abundance
39- 43 A5 --- NMm "NM/BC" Indicates a non-member and/or a
binary candidate
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Note (1): The MAD statistic is a robust estimator of variance, constructed by
comparing the [Fe/H] value for each star to the median value for that
particular absorption line.
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History:
From electronic version of the journal
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(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Apr-2015