J/A+A/664/A93 Northern WNE star spectra (Dsilva+, 2022)
A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars.
II. The northern WNE sequence.
Dsilva K., Shenar T., Sana H., Marchant P.
<Astron. Astrophys., 664, A93 (2022)>
=2022A&A...664A..93D 2022A&A...664A..93D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Spectra, optical
Keywords: stars: Wolf-Rayet - techniques: radial velocities -
binaries: spectroscopic - stars: evolution
Abstract:
Most massive stars reside in multiple systems that will interact over
the course of their lifetime. This has important consequences on their
future evolution and their end-of-life products. Classical Wolf-Rayet
(WR) stars represent the final end stages of stellar evolution at the
upper-mass end. While their observed multiplicity fraction is reported
to be ∼0.4 in the Galaxy, their intrinsic multiplicity properties and
the distributions of their orbital parameters remain insufficiently
constrained to provide a reliable anchor to compare to evolutionary
predictions.
As part of a homogeneous, magnitude-limited (V≤12) spectroscopic
survey of northern Galactic WR stars, this paper aims to establish the
observed and intrinsic multiplicity properties of the early-type
nitrogen-rich WR population (WNE), including estimates of the
multiplicity fraction and the shape of their orbital period
distribution. Additionally, we compare these with the properties of
the carbon-rich WR population (WC) stars obtained in the first paper
of this series.
We obtained high-resolution spectroscopic time series of the complete
magnitude-limited sample of 16 WNE stars observable with the 1.2m
Mercator telescope at La Palma, typically providing a time base of
about two to eight years. We measured relative radial velocities (RVs)
using cross-correlation and used RV variations to flag binary
candidates. Using an updated Monte Carlo method with a Bayesian
framework, we calculated the three-dimensional likelihood for the
intrinsic binary fraction (fintWNE), the maximum period (log
Pmax), and the power-law index for the period distribution (π)
for the WNE population with Pmin fixed at 1d.
We also used this updated method to re-derive multiplicity parameters
for the Galactic WC population. Results. Adopting a peak-to-peak RV
variability threshold of 50km/s as a criterion, we classify 7 of the
16 targets as binaries. This results in an observed multiplicity
fraction (fobsWNE) of 0.44±0.12. Assuming flat priors, we derive
the best-fit multiplicity properties fintWNE=0.56-0.15+0.20,
logPmax=4.60-0.77+0.40, and π=-0.30-0.53+0.55 for the
parent WNE population. We explored different mass-ratio distributions
and note that they did not change our results significantly. For the
Galactic WC population from Paper I, we re-derive
fintWC=0.96-0.22+0.04, logPmin=0.75-0.60+0.26,
logPmax=4.00-0.34+0.42, and π=1.90-1.25+1.26.
The derived multiplicity parameters for the WNE population are quite
similar to those derived for main-sequence O binaries but differ from
those of the WC population. The significant shift in the WC period
distribution towards longer periods is too large to be explained via
expansion of the orbit due to stellar winds, and we discuss possible
implications of our results. Analysis of the WNL population and
further investigation of various evolutionary scenarios is required to
connect the different evolutionary phases of stars at the upper-mass
end.
Description:
The spectra used in this analyses are provided here.
Each FITS file has hdu tables that contain the wavelength, normalised
flux and the error on the flux.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 43 16 WNE stars in our RV monitoring campaign
list.dat 85 260 List of fits spectra
fits/* . 260 Individual fits spectra
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Star Star name
7- 8 I2 h RAh Simbad right ascension (J2000)
10- 11 I2 min RAm Simbad right ascension (J2000)
13- 17 F5.2 s RAs Simbad right ascension (J2000)
19 A1 --- DE- Simbad declination sign (J2000)
20- 21 I2 deg DEd Simbad declination (J2000)
23- 24 I2 arcmin DEm Simbad declination (J2000)
26- 29 F4.1 arcsec DEs Simbad declination (J2000)
31- 32 I2 --- Nsp Number of spectra
34- 39 F6.1 d Time Time baseline of coverage
41- 43 I3 --- S/N Average S/N per resolution element at 4400Å
({DELTA}λ=0.05Å)
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Star Star name
7- 12 I6 --- Nx Number of pixels along X-axis
14- 39 A26 "datime" Obs.date Observation date
41- 47 F7.5 [0.1nm] loglambda Wavelength
49- 52 I4 Kibyte size Size of FITS file
54- 70 A17 --- FileName Name of FITS file, in subdirectory fits
72- 85 A14 --- Title Title of the FITS file
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Acknowledgements:
Karah Dsilva, karan.singh.dsilva(at)ulb.be
References:
Dsilva et al., Paper I 2020A&A...641A..26D 2020A&A...641A..26D
(End) Patricia Vannier [CDS] 24-May-2023