J/AJ/113/1045 BV photometry of NGC 3680 (Kozhurina-Platais+ 1997)
The age of NGC 3680 and a test of convective overshoot.
Kozhurina-Platais V., Demarque P., Platais I., Orosz J.A., Barnes S.
<Astron. J. 113, 1045 (1997)>
=1997AJ....113.1045K 1997AJ....113.1045K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, CCD
Abstract:
A new CCD BV color-magnitude diagram (CMD) has been derived for the
intermediate age open cluster NGC 3680. The quality of photometry
coupled with the best-to-date knowledge of cluster memberships allows
for a detailed isochrone fit to the CMD. The theoretical isochrones
have been constructed using the Yale Rotating Evolution Code (YREC) in
its non-rotating mode and the OPAL opacities (circa 1991). Four sets
of isochrones have been calculated: one for the standard stellar model
calibrated to the Sun and three others for models with different
amounts of convective overshoot at the edge of the convective core,
namely, 0.15, 0.20, and 0.25Hp, where Hp is the pressure scale
height at the core edge. All four sets of theoretical isochrones were
adjusted to an adopted distance modulus of V0-MV=10.20 and
reddening E(B-V)=0.075 which leads to ages of 1.3±0.15, 1.5±0.15,
1.6±0.15, and 1.7±0.15Gyr, respectively The uncertainties in age
mainly reflect a subjective decision in differentiating a good fit
from a poorer one The model with a convective overshoot of 0.20Hp
seems to yield the best fit to the sharply curved upper main sequence.
Hence, the estimated age of NGC 3680 is 1.6±0.15Gyr. The adopted
overshoot parameter ostensibly is uncertain by ±0.05Hp. For
comparison, the same stellar models with overshoot of 0.25Hp were
fit to the color-magnitude diagram of the cluster NGC 752, which is
similar in age and composition to NGC 3680 The age estimate for NGC
752 is 1.6±0.2Gyr, assuming V0-MV=8.20 and E(B-V)=0.030 for the
cluster.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3 62 146 The BV CCD photometry for probable cluster
stars in NGC 3680
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See also:
I/212 : Proper motions in NGC 3680 (Kozhurina-Platais+, 1995)
J/A+AS/118/407 : NGC 3680 CCD photometry & velocities (Nordstroem+ 1996)
J/A+A/322/460 : NGC 3680 photometry and radial velocities (Nordstrom+ 1997)
Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star [777/1873]+= Star number
5 A1 --- m_Star Multiplicity index on Star number
6- 7 A2 --- n_Star [ab ] Note on Star (1)
9- 10 I2 h RAh [11] Right ascension (J2000)
12- 13 I2 min RAm [24/26]+= Right ascension (J2000)
15- 19 F5.2 s RAs Right ascension (J2000)
21 A1 --- DE- [-] Declination sign
22- 23 I2 deg DEd [43] Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 31 F4.1 arcsec DEs Declination (J2000)
33- 38 F6.3 mag Vmag V magnitude
40- 44 F5.3 mag B-V B-V magnitude
46- 50 F5.3 mag e_Vmag rms uncertainty on Vmag
52- 56 F5.3 mag e_Bmag rms uncertainty on Bmag
58- 59 I2 --- o_Vmag Number of individual CCD observations
61- 62 I2 % Member ? Proper motion membership probability
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Note (1): a : B, V-photometry from other studies (see Sec. 2.2).
b : Adopted binaries (see Sec. 3.2).
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 03-Oct-1997