J/A+A/457/265 The VLT-FLAMES Survey of Massive Stars (Dufton+, 2006)
The VLT-FLAMES Survey of Massive Stars:
Stellar parameters and rotational velocities in NGC 3293, NGC 4755 and NGC 6611.
Dufton P.L., Smartt S.J., Lee J.K, Ryans R.S.I., Hunter I., Evans C.J.,
Herrero A., Trundle C., Lennon D.J., Irwin M.J., Kaufer A.
<Astron. Astrophys. 457, 265 (2006)>
=2006A&A...457..265D 2006A&A...457..265D
ADC_Keywords: Milky Way ; Clusters, open ; Stars, OB; Stars, atmospheres ;
Rotational velocities
Keywords: star: early-type - stars: fundamental parameters - stars: rotation -
Hertzsprung-Russell (HR) and C-M diagrams - stars: evolution
Abstract:
An analysis is presented of VLT-FLAMES spectroscopy for three Galactic
clusters, NGC 3293, NGC 4755 and NGC 6611. Non-LTE model atmosphere
calculations have been used to estimate effective temperatures (from
either the helium spectrum or the silicon ionization equilibrium) and
gravities (from the hydrogen spectrum). Projected rotational
velocities have been deduced from the helium spectrum (for fast and
moderate rotators) or the metal line spectrum (for slow rotators). The
origin of the low gravity estimates for apparently near main sequence
objects is discussed and is related to the stellar rotational
velocity. The atmospheric parameters have been used to estimate
cluster distances (which are generally in good agreement with previous
determinations) and these have been used to estimate stellar
luminosities and evolutionary masses. The observed Hertzsprung-Russell
diagrams are compared with theoretical predictions and some
discrepancies including differences in the main sequence luminosities
are discussed. Cluster ages have been deduced and evidence for
non-coeval star formation is found for all three of the clusters.
Projected rotational velocities for targets in the older clusters,
NGC 3293 and NGC 4755, have been found to be systematically larger
than those for the field, confirming recent results in other similar
age clusters. The distribution of projected rotational velocities are
consistent with a Gaussian distribution of intrinsic rotational
velocities. For the relatively unevolved targets in the older
clusters, NGC 3293 and NGC 4755, the peak of the velocity distribution
would be 250km/s with a full-width-half-maximum of approximately
180km/s. For NGC 6611, the sample size is relatively small but implies
a lower mean rotational velocity. This may be evidence for the
spin-down effect due to angular momentum loss through stellar winds,
although our results are consistent with those found for very young
high mass stars. For all three clusters we deduce present day mass
functions with Gamma-values in the range of -1.5 to -1.8, which are
similar to other young stellar clusters in the Milky Way.
Description:
Tables 7, 8 and 9 contain observational and atmospheric parameters,
rotational velocities, luminosities and masses of objects in the
Galactic clusters NGC 3293, NGC 4755 and NGC 6611 respectively. See
Evans et al. (2005, Cat. J/A+A/437/467) for detail of the observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 83 92 Details of NGC 3293 objects
table8.dat 83 88 Details of NGC 4755 objects
table9.dat 83 44 Details of NGC 6611 objects
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See also:
J/A+A/437/467 : VLT-FLAMES survey of massive stars (Evans+, 2005)
Byte-by-byte Description of file: table7.dat table8.dat table9.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star Name (1)
9 A1 --- f_Name [*] *: stars lie outside the criteria for
cluster membership
11- 15 F5.2 mag Vmag V magnitude
17- 21 F5.2 --- B-V B-V colour index
23- 36 A14 --- SpType MK spectral type
38- 42 I5 K Teff ? Effective Temperature
44- 47 F4.2 [cm/s2] logg ? logarithmic surface gravity
48 A1 --- u_logg Uncertainty flag on logg (2)
50- 52 A3 --- Method Methodology (3)
54- 56 I3 km/s vsini Projected rotational velocity
57 A1 --- u_vsini Uncertainty flag on vsini (2)
59- 62 F4.2 mag E(B-V) ? E(B-V) reddening
64- 67 F4.2 [solLum] logL ? logarithmic luminosity
69- 72 F4.1 solMass Mass ?=- Mass
74- 76 I3 km/s RV ? Radial velocity
77 A1 --- u_RV Uncertainty flag on vsini (2)
79- 83 F5.2 arcmin Dist Radial distance from cluster center
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Note (1): Stars, NNNN-NNN are identified in Simbad as Cl* NGC NNN ESL NNN.
Note (2): A colon indicates additional uncertainty
Note (3): The specific method used to determine the atmospheric parameters
are designated as follows:
He = from neutral helium and hydrogen equivalent widths
He+ = from ionized helium
Si = Si III/Si IV ionization equilibrium and hydrogen line profiles
A = effective temperature adopted
I = effective temperature interpolated
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Acknowledgements: Ian Hunter, i.hunter(at)qub.ac.uk
(End) Patricia Vannier [CDS] 11-Jul-2006