J/MNRAS/499/1312 Properties of stars in open cluster NGC 2506 (Knudstrup+, 2020)
Extremely precise age and metallicity of the open cluster NGC 2506 using
detached eclipsing binaries.
Knudstrup E., Grundahl F., Brogaard K., Slumstrup D., Orosz J.A.,
Sandquist E.L., Jessen-Hansen J., Lund M.N., Arentoft T., Tronsgaard R.,
Yong D., Frandsen S., Bruntt H.
<Mon. Not. R. Astron. Soc., 499, 1312-1339 (2020)>
=2020MNRAS.499.1312K 2020MNRAS.499.1312K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Positional data ; Photometry, uvby ;
Radial velocities
Keywords: binaries: eclipsing - binaries: spectroscopic - stars: oscillations -
Galaxy: open clusters and associations: individual
Abstract:
Accurate stellar parameters of stars in open clusters can help
constrain models of stellar structure and evolution. Here, we wish to
determine the age and metallicity content of the open cluster NGC
2506. To this end, we investigated three detached eclipsing binaries
(DEBs; V2032, V4, and V5) for which we determined their masses and
radii, as well as four red giant branch stars for which we determined
their effective temperatures, surface gravities, and metallicities.
Three of the stars in the DEBs have masses close to the cluster
turn-off mass, allowing for extremely precise age determination.
Comparing the values for the masses and radii of the binaries to BaSTI
(a Bag of Stellar Tracks and Isochrones) isochrones, we estimated a
cluster age of 2.01±0.10Gyr. This does depend on the models used in
the comparison, where we have found that the inclusion of convective
core-overshooting is necessary to properly model the cluster. From red
giant branch stars, we determined values for the effective
temperatures, the surface gravities, and the metallicities. From these
we find a cluster metallicity of -0.36±0.10dex. Using this value and
the values for the effective temperatures, we determine the reddening
to be E(b-y)=0.057±0.004mag. Furthermore, we derived the distance to
the cluster from Gaia parallaxes and found 3.101±0.017kpc, and we
have performed a radial velocity membership determination for stars in
the field of the cluster. Finally, we report on the detection of
oscillation signals in γ Dor and δ Scuti members in data
from the Transiting Exoplanet Survey Satellite (TESS) mission,
including the possible detection of solar-like oscillations in two of
the red giants.
Description:
We obtained 15 epochs of GIRAFFE spectroscopy (ESO programme
075.D-0206(B)) from European Southern Observatory's (ESO's) Very Large
Telescope (VLT) for NGC 2506 in order to define membership near the
cluster turn-off region and RGB. The setting (HR14A) with a central
wavelength near 6515Å and a resolution of 18000 (Medusa mode) was
utilized. All spectra were recovered from the
http://giraffe-archive.obspm.fr site, which provided a re-reduction of
the ESO GIRAFFE data. We note, however, that at the time of writing,
this webpage is no longer active.
To derive the velocities, we cross-correlated each obtained stellar
spectrum with a solar template and calculated the average velocity,
standard deviation of the individual velocities as well as the width
of the fitted Gaussian. This resulted in a histogram of velocities for
122 objects, with a clear peak in the distribution at vrad=83.8km/s
with a full width half-maximum (FWHM) of 4.7km/s. We then assigned
membership by requiring that an object has an average velocity within
two FWHM of the cluster mean.
In Table A2, the basic information for each target is provided; ID,
uvby Stromgren photometry, average velocity, standard deviation of the
15 RVs, and the Gaussian σ from the fit to the cross-correlation
function (CCF). The two second to last columns indicate whether a
significant epoch-to-epoch variability was found and the membership
status.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea2.dat 122 123 Table containing the results of our
spectroscopic membership determination in
Section 3.1
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See also:
J/AJ/152/192 : WOCS. LXXII. A uvbyCaHb study of NGC 2506
(Anthony-Twarog+, 2016)
J/A+A/633/A99 : Gaia DR2 open clusters in the Milky Way. II
(Cantat-Gaudin+, 2020)
J/AJ/155/138 : WOCS.LXXVI.Velocity & abundances in NGC2506
(Anthony-Twarog+, 2018)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Star name (1)
7 A1 --- f_Name [X] Flag on Name (2)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 18 F4.1 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 30 F4.1 arcsec DEs Declination (J2000)
32- 37 F6.3 mag umag Stromgren u-band magnitude
39- 44 F6.4 mag e_umag Error on umag
46- 51 F6.3 mag vmag Stromgren v-band magnitude
53- 58 F6.4 mag e_vmag Error on vmag
60- 65 F6.3 mag bmag Stromgren b-band magnitude
67- 72 F6.4 mag e_bmag Error on bmag
74- 79 F6.3 mag ymag Stromgren y-band magnitude
81- 86 F6.4 mag e_ymag Error on ymag
88- 95 F8.3 km/s RV Radial velocity
97- 103 F7.3 km/s e_RV Error on RV
105- 110 F6.3 km/s s_RV Gaussian σ from the fit to the
cross-correlation function (CCF)
112 I1 --- Var [0/1] Indicates if the star is a variable
(1:yes, 0:no)
114 I1 --- Mem [0/1] Indicates if the star is a member
(1:yes, 0:no)
116- 118 F3.1 --- Pmem Membership probability derived by
Cantat-Gaudin & Anders (2020A&A...633A..99C 2020A&A...633A..99C,
Cat. J/A+A/633/A99)
120- 122 A3 --- Class Membership class determined in Anthony-Twarog
et al. (2018AJ....155..138A 2018AJ....155..138A, Cat. J/AJ/155/138)
(3)
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Note (1): The naming is the WEBDA identification number found from
cross-matching with Anthony-Twarog et al. (2016AJ....152..192A 2016AJ....152..192A,
Cat. J/AJ/152/192), except for names starting with K, where we could
not find a match and they therefore refer to their index in our
Stromgren photometry.
A name ending with X denotes that the star has been excluded.
Note (2): Flag as follows:
X = Indicates this star has been excluded
Note (3): Class as follows:
M = probable RV member
NM = non-member
MB = probable binary member
MN = RV member with proper motion membership below 50 per cent
B = probable binary for which the RV deviates significantly from the mean
BNM = binary with deviant RV, but proper motion probability below 50 per
cent
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 17-Aug-2023