J/A+A/615/A19 HD54662 radial velocities and X-ray light curves (Mossoux+, 2018)
The long-period massive binary HD 54662 revisited.
Mossoux E., Mahy L., Rauw G.
<Astron. Astrophys. 615, A19 (2018)>
=2018A&A...615A..19M 2018A&A...615A..19M (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Stars, O ; Radial velocities ;
X-ray sources ; Spectroscopy
Keywords: stars: early-type - stars: massive - binaries: spectroscopic -
stars: individual: HD 54662
Abstract:
HD 54662 is an O-type binary star belonging to the CMa OB1
association. Due to its long-period orbit, this system is an
interesting target to test the adiabatic wind shock model. The goal of
this study is to improve our knowledge of the orbital and stellar
parameters of HD 54662 and to analyze its X-ray emission to test the
theoretical scaling of X-ray emission with orbital separation for
adiabatic wind shocks. A spectral disentangling code is applied to a
set of optical spectra to determine the radial velocities, as well as
the individual spectra of the primary and secondary stars. The orbital
solution of the system is established and the reconstructed individual
spectra are analyzed by means of the CMFGEN model atmosphere code. Two
X-ray spectra are fitted using a Markov Chain Monte Carlo algorithm
and are compared to the emission expected from adiabatic shocks. We
determine an orbital period of 2103.4 days, a surprisingly low orbital
eccentricity of 0.11, and a mass ratio m2/m1 of 0.84. Combined with
the orbital inclination inferred in a previous astrometric study, we
obtain surprisingly low masses of 9.7 and 8.2M☉. From the
disentangled primary and secondary spectra, we infer O6.5 spectral
types for both stars with the primary being about two times brighter
than the secondary. The softness of the X-ray spectra for the two
observations, the very small variation of best-fitting spectral
parameters and the comparison of the X-ray-to- bolometric luminosity
ratio with the canonical value for O-type stars allow us to conclude
that the X-ray emission from the wind interaction region is quite
small and that the observed emission is rather dominated by the
intrinsic emission from the stars. Computing the peculiar radial and
intrinsic emission from the stars. Computing the peculiar radial and
tangential velocities, we cannot confirm the runaway status previously
attributed to HD 54662. We find no X-ray emission associated with the
bow shock detected in the infrared. The lack of hard X-ray emission
from the wind-shock region suggests that the mass-loss rates are lower
than expected and/or that the pre-shock wind velocities are much lower
than the terminal wind velocities. The bow shock associated with HD
54662 possibly corresponds to a wind-blown arc created by the
interaction of the stellar winds with the ionized gas of the CMa OB1
association rather than by a large differential velocity between the
binary and the surrounding interstellar medium.
Description:
Optical radial velocities of HD 54662 determined from optical
spectroscopy with the TIGRE telescope, the Canada-France-Hawaii
Telescope (CFHT), the Nordic Optical Telescope and the Very Large
Telescope UT2. We also provide X-ray spectra of HD 54662 taken with
XMM-Newton.
Objects:
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RA (2000) DE Designation(s)
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07 09 20.25 -10 20 47.6 HD 54662 = HR 2694
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
rv.dat 35 39 Radial velocities (Table 1)
pnsp14.dat 13 41 pn spectrum for the 2014 observation
mos1sp14.dat 13 11 MOS1 spectrum for the 2014 observation
mos2sp14.dat 13 13 MOS2 spectrum for the 2014 observation
pnsp16.dat 13 45 pn spectrum for the 2016 observation
mos1sp16.dat 13 31 MOS1 spectrum for the 2016 observation
mos2sp16.dat 13 39 MOS2 spectrum for the 2016 observation
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Byte-by-byte Description of file: rv.dat
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Bytes Format Units Label Explanations
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1- 9 F9.4 d HJD Julian date of the observation (HJD-2450000)
11- 14 F4.1 km/s RV1 Radial velocity of the primary (1)
16- 19 F4.1 km/s RV2 Radial velocity of the secondary (1)
21- 35 A15 ---- Inst Instrument used for the observation
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Note (1): The RVs are determined with the spectral disentangling routine for
the spectral regions from 4050-4890Å and around the HeI 5876 line
(see Sect. 3.1). Typical uncertainties on RVs are 2km/s for the primary and
5km/s for the secondary.
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Byte-by-byte Description of file: mos*.dat pn*.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 keV Energy Energy of the spectral bin
8- 13 F6.4 ct/s/keV Flux Normalized flux in the spectral bin
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Acknowledgements:
Enmanuelle Mossoux, emossoux(at)uliege.be
(End) E. Mossoux [STAR, Uliege, Belgium], P. Vannier [CDS] 12-Feb-2018