J/ApJ/947/77 Radial velocity study of six known WN3/O3 stars (Massey+, 2023)
Constraints on the binarity of the WN3/O3 class of Wolf-Rayet stars.
Massey P., Neugent K.F., Morrell N.I.
<Astrophys. J., 947, 77 (2023)>
=2023ApJ...947...77M 2023ApJ...947...77M
ADC_Keywords: Stars, Wolf-Rayet; Radial velocities; Spectra, optical;
Magellanic Clouds
Keywords: Massive stars ; Wolf-Rayet stars ; Stellar evolution
Abstract:
The WN3/O3 Wolf-Rayet (WR) stars were discovered as part of our survey
for WRs in the Magellanic Clouds. The WN3/O3s show the emission lines
of a high-excitation WN star and the absorption lines of a hot O-type
star, but our prior work has shown that the absorption spectrum is
intrinsic to the WR star. Their place in the evolution of massive
stars remains unclear. Here we investigate the possibility that they
are the products of binary evolution. Although these are not WN3+O3 V
binaries, they could still harbor unseen companions. To address this
possibility, we have conducted a multiyear radial velocity study of
six of the nine known WN3/O3s. Our study finds no evidence of
statistically significant radial velocity variations, and allows us to
set stringent upper limits on the mass of any hypothetical companion
star: for probable orbital inclinations, any companion with a period
less than 100 days must have a mass <2M☉. For periods less than
10 days, any companion would have to have a mass <1M☉. We argue
that scenarios where any such companion is a compact object are
unlikely. The absorption lines indicate a normal projected rotational
velocity, making it unlikely that these stars evolved with the aid of
a companion star that has since merged. The modest rotation also
suggests that these stars are not the result of homogenous evolution.
Thus it is likely that these stars are a normal but short-lived stage
in the evolution of massive stars.
Description:
We obtained enough spectra for six WN3/O3 Wolf-Rayet (WR) stars to
adequately look for the presence of lower-mass companions. Our
discovery spectra were all taken with the Las Campanas Magellan
Echellette (MagE) spectrograph, and we continued to use this
instrument for our follow-up radial velocity measurements. For the
data taken in 2014 and 2015, the instrument was mounted on the Clay
6.5m Magellan telescope, after which the instrument was moved to the
Baade 6.5m Magellan telescope. Our exposures ranged from a single
10min exposure to an hour (3x20min) and span 2013-Oct-16 to 2022-Oct-31.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 55 6 WN3/O3 stars in this radial velocity study
table2.dat 46 63 Journal of observations
table3.dat 56 169 Radial Velocity Measurements
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See also:
III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)
J/ApJ/682/L117 : A spectroscopic orbit for Regulus (Gies+, 2008)
J/ApJ/748/96 : Massive binaries in the LMC (Massey+, 2012)
J/A+A/565/A27 : Wolf-Rayet stars in Large Magellanic Cloud (Hainich+, 2014)
J/ApJ/789/139 : Three O-type binaries photometry in LMC (Morrell+, 2014)
J/ApJ/789/10 : M33 WR and Of-type Stars (Neugent+, 2014)
J/ApJ/863/181 : The fifth catalog of LMC Wolf-Rayet stars (Neugent+, 2018)
J/MNRAS/493/1512 : Galactic Wolf-Rayet stars with Gaia DR2 I (Rate+, 2020)
J/ApJ/922/177 : 2MASS red supergiants in the SMC (Massey+, 2021)
J/AJ/163/171 : The EXPRES Stellar Signals Project. II. RVel (Zhao+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11- 12 I2 h RAh Hour of right ascension (J2000)
14- 15 I2 min RAm Minute of right ascension (J2000)
17- 21 F5.2 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of declination (J2000)
35- 39 F5.2 mag Vmag [15.8/16.7] V magnitude
41- 45 F5.2 mag B-V [-0.25/-0.12] B-V colour index
47- 50 F4.1 mag VMag [-3.1/-2.3] Absolute V magnitude
52- 53 I2 --- Nobs [9/13] Number of observations
55 I1 --- Nsup [6/9] Number of spectra with S/N>100
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11- 21 A11 "Y/M/D" Date Date of observation (UT)
23- 33 F11.3 d HJD Heliocentric Julian Date
35- 40 A6 s ExpTime Exposure time
42- 44 I3 --- S/N [50/195] Signal-to-noise ratio (1)
46 A1 --- ID Designation
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Note (1): Signal-to-noise ratio per 3-pixel spectral resolution element
measured over the region 4210-4330Å.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name WN3/O3 star in this radial velocity study
11- 21 A11 --- Pair Cross Pair (1)
23- 27 F5.1 km/s RVel1 [-18/19] Radial Velocity, NVλ4946
29- 33 F5.1 km/s RVel2 [-46/32] Radial Velocity,
NV+HeIIλ4603-4686
35- 39 F5.1 km/s RVel3 [-23/25] Radial Velocity,
Hδ/HeIIλ4100
41- 45 F5.1 km/s RVel4 [-53/43] Radial Velocity,
Hγ/HeIIλ4339
47- 51 F5.1 km/s RVavg [-17/15] Mean, RVel1-4
53- 56 F4.1 km/s s_RVavg [1.8/33]? Standard deviation, RVel1-4
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Note (1): Identification of pair spectra are given by the "ID" column
in Table 2. The last row of each star (sigma-pairs) gives the standard
deviation of the line measurement across all pairs for that wavelength
regime.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Apr-2025