J/ApJ/789/139 Three O-type binaries photometry in LMC (Morrell+, 2014)
Photometric and spectroscopic studies of massive binaries in the Large
Magellanic Cloud.
II. Three O-type systems in the 30 Dor region.
Morrell N.I., Massey P., Neugent K.F., Penny L.R., Gies D.R.
<Astrophys. J., 789, 139 (2014)>
=2014ApJ...789..139M 2014ApJ...789..139M (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, O ; Photometry ;
Binaries, spectroscopic
Keywords: binaries: eclipsing - binaries: spectroscopic - stars: early-type -
stars: fundamental parameters -
stars: individual: [M2002] LMC 169782, [M2002] LMC 171520, [P93] 921
Abstract:
This is the second paper in a series devoted to the study of massive
binary systems in the Large Magellanic Cloud (LMC). We mainly aim to
provide accurate data that constrains the mass-luminosity relation for
the most massive stars but also to address the long lasting problem
known as the "mass discrepancy." We present here our results for three
binaries (LMC 169782, LMC 171520, and [P93] 921) harboring the
earliest O-type components-ranging from O4 V to O6.5 V-among our
sample of 17 systems. Our photometry provided accurate periods for the
studied systems, allowing the spectroscopic observations to be
performed at selected phases where the radial velocity separation
between binary components is larger. Following the procedure outlined
in our first paper of this series, after solving the radial velocity
curves for orbital parameters, we used tomographic reconstruction to
obtain the individual spectra of each star, from which we determined
effective temperatures via a model atmosphere fitting with FASTWIND.
This information, combined with the light-curve analysis that was
performed with GENSYN, enabled the determination of absolute masses,
radii, and bolometric luminosities that are compared with those
predicted by modern stellar evolutionary models finding that they
agree within the uncertainties. Nevertheless, the comparison seems to
confirm the small differences found in the first paper of this series
in the sense that the evolutionary masses are slightly larger than the
Keplerian ones, with differences averaging ∼10%, or alternatively, the
stellar evolutionary models predict luminosities that are somewhat
lower than observed. Still, the overall agreement between the current
evolutionary models and the empirically determined stellar parameters
is remarkable.
Description:
We will concentrate on the presentation and discussion of our
photometric and spectroscopic observations of 3 binary systems
containing the earliest type components among the observed sample of
17 binaries in the LMC, namely, LMC 169782, LMC 171520, and [P93] 921.
All three systems belong to the 30 Dor region, which harbors some of
the most massive stars known to date (Crowther et al.
2010MNRAS.408..731C 2010MNRAS.408..731C; Schnurr et al. 2009MNRAS.395..823S 2009MNRAS.395..823S).Time-resolved
photometry was carried out for all three systems in order to provide
the light curves needed to establish periods and calculate orbital
inclinations. As described in Paper I (Massey et al.
2012ApJ...748...96M 2012ApJ...748...96M), this was carried out using simple aperture
photometry as opposed to point-spread-function fitting; tests showed
that we obtained equally accurate results with aperture photometry,
which was expected given that our targets are not overly crowded. In
order to compute the observed absolute magnitudes for our targets, we
have assumed a distance modulus of 18.50 (50 kpc) for the LMC
following van den Bergh (2000, The Galaxies of the Local Group
(Cambridge: Cambridge Univ. Press)), and we have used the intrinsic
colors given by FitzGerald (1970A&A.....4..234F 1970A&A.....4..234F) and a normal
reddening law with Rv = 3.1.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
05 37 59.44 -69 09 01.0 [M2002] LMC 169782 = VFTS 217
05 38 41.23 -69 02 58.3 [M2002] LMC 171520 = VFTS 500
05 38 42.10 -69 05 45.4 [P93] 921 = VFTS 522
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 34 342 LMC 169782 Photometry
table6.dat 34 269 LMC 171520 Photometry
table9.dat 34 444 [P93] 921 Photometry
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See also:
J/MNRAS/349/833 : uVI photometry of 3 LMC eclipsing binaries (Bayne+, 2004)
J/AJ/131/407 : BV photometry of stars in the LMC (Kaluzny+, 2006)
J/ApJ/748/96 : Massive binaries in the LMC (Massey+, 2012)
Byte-by-byte Description of file: table2.dat table6.dat table9.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date
14- 19 F6.3 mag Vmag Observed V band magnitude
21- 25 F5.3 mag e_Vmag The 1σ error in Vmag
27 I1 --- Tel [1/3] Telescope code (1)
29- 34 F6.3 --- Phase Orbital phase (2)
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Note (1): Flag as follows :
1 = SITe#3 on Swope 1.0-m;
2 = Y4KCam on SMARTS Yale 1.0-m;
3 = ANDICAM on SMARTS 1.3-m.
Note (2): Orbital phase :
Table 2 : Based upon P = 1.855280 days and T = 2453285.909.
Table 6 : Based upon P = 2.875275 days and T = 2453287.010.
Table 9 : Based upon P = 2.389321 days and T = 2453285.541.
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History:
From electronic version of the journal
References:
Massey et al., Paper I, 2012ApJ...748...96M 2012ApJ...748...96M, Cat. J/ApJ/748/96
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 10-Mar-2017