J/A+A/663/A36 Most massive stars and their clumped winds (Brands+, 2022)
The R136 star cluster dissected with Hubble Space Telescope/STIS.
III. The most massive stars and their clumped winds.
Brands S.A., de Koter A., Bestenlehner J.M., Crowther P.A., Sundqvsit J.O.,
Puls J., Caballero-Nieves S.M., Abdul-Masih M., Driessen F.A., Garcia M.,
Geen S., Graefener G., Hawcroft C., Kaper L., Keszthelyi Z., Langer N.,
Sana H., Schneider R.N., Shenar T., Vink J.S.
<Astron. Astrophys. 663, A36 (2022)>
=2022A&A...663A..36B 2022A&A...663A..36B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, O ; Stars, OB ; Stars, supergiant ; Stars, ages ;
Spectroscopy ; Ultraviolet ; Effective temperatures ;
Fundamental catalog ; Mass loss
Keywords: stars: massive - stars: mass-loss - stars: winds, outflows -
stars: fundamental parameters - Magellanic Clouds -
galaxies: star clusters: individual: R136
Abstract:
The star cluster R136 inside the Large Magellanic Cloud hosts a rich
population of massive stars, including the most massive stars known.
The strong stellar winds of these very luminous stars impact their
evolution and the surrounding environment. We currently lack detailed
knowledge of the wind structure that is needed to quantify this
impact.
To observationally constrain the stellar and wind properties of the
massive stars in R136, in particular the wind-structure parameters
related to wind clumping.
We simultaneously analyse optical and ultraviolet spectroscopy of 53
O-type and 3 WNh-stars using the Fastwind model atmosphere code and a
genetic algorithm. The models account for optically thick clumps and
effects related to porosity and velocity- porosity, as well as a
non-void interclump medium.
We obtain stellar parameters, surface abundances, mass-loss rates,
terminal velocities and clumping characteristics and compare these to
theoretical predictions and evolutionary models. The clumping
properties include the density of the interclump medium and the
velocity-porosity of the wind. For the first time, these
characteristics are systematically measured for a wide range of
effective temperatures and luminosities.
We confirm a cluster age of 1.0-2.5Myr and derive an initial stellar
mass of ≥250M☉ for the most massive star in our sample, R136a1.
The winds of our sample stars are highly clumped, with an average
clumping factor of fcl=29±15. We find tentative trends in the
wind-structure parameters as a function of mass-loss rate, suggesting
that the winds of stars with higher mass-loss rates are less clumped.
We compare several theoretical predictions to the observed mass-loss
rates and terminal velocities and find that none satisfactorily
reproduces both quantities. The prescription of Krticka & Kubat
matches best the observed mass-loss rates.
Description:
Spectroscopic parameters for 53 O-type and 3 WNh stars in the core of
the cluster R136. For each of the stars, we carried out an optical only
analysis, and a simultaneous optical and UV analysis. With Bonnsai, we
derived evolutionary parameters for all stars, based on the parameters
resulting from the optical and UV analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 45 56 List of studied source
tablea1.dat 212 39 Optical+UV parameters (nfree = 12-14)
tablea2.dat 120 17 Optical+UV parameters (nfree = 6)
tablei1.dat 113 56 Additional quantities optical+UV fit
tablei2.dat 126 55 Optical only fit
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See also:
J/ApJ/448/179 : HST photometry in R136 (Hunter+ 1995)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Source Source name (G1)
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 21 F6.3 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 34 F5.2 arcsec DEs Declination (J2000)
37- 45 A9 --- SName Simbad name
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Name of the source (G1)
8- 11 F4.2 [Lsun] logL Logarithmic luminosity in terms of solar
13- 16 F4.2 [Lsun] E_logL Upper CI of logL
18- 21 F4.2 [Lsun] e_logL Lower CI of logL
23- 27 I5 K Teff Effective temperature
29- 32 I4 K E_Teff Upper CI of Teff
34- 37 I4 K e_Teff Lower CI of Teff
39- 42 F4.2 [cm/s2] logg logarithmic surface gravity
44- 47 F4.2 [cm/s2] E_logg Upper CI of logg
49- 52 F4.2 [cm/s2] e_logg Lower CI of logg
54- 57 F4.1 Rsun R Stellar radius
59- 61 F3.1 Rsun E_R Upper CI of R
63- 65 F3.1 Rsun e_R Lower CI of R
67- 71 F5.2 Msun/yr Mdot Logarithmic mass-loss rate
73- 76 F4.2 Msun/yr E_Mdot Upper CI of Mdot
78- 81 F4.2 Msun/yr e_Mdot Lower CI of Mdot
83- 86 I4 km/s vinf Terminal outflow velocity
88- 90 I3 km/s E_vinf Upper CI of vinf
92- 94 I3 km/s e_vinf Lower CI of vinf
96- 99 F4.2 km/s wturb Fractional wind turbulence (2)
101-104 F4.2 km/s E_wturb Upper CI of wturb
106-109 F4.2 km/s e_wturb Lower CI of wturb
111-112 I2 --- fclump Clumping factor
114-115 I2 --- E_fclump Upper CI of fclump
117-118 I2 --- e_fclump Lower CI of fclump
120-123 F4.2 --- fic Interclump density contrast (3)
125-128 F4.2 --- E_fic Upper CI of fic
130-133 F4.2 --- e_fic Lower CI of fic
135-138 F4.2 --- fvel Velocity-porosity (4)
140-143 F4.2 --- E_fvel Upper CI of fvel
145-148 F4.2 --- e_fvel Lower CI of fvel
150-153 F4.2 --- beta Wind acceleration parameter beta
155-158 F4.2 --- E_beta Upper CI of beta
160-163 F4.2 --- e_beta Lower CI of beta
165-168 F4.2 --- vclst Fractional onset velocity of clumping (5)
170-173 F4.2 --- E_vclst Upper CI of vclst
175-178 F4.2 --- e_vclst Lower CI of vclst
180-183 F4.2 --- C Carbon abundance (6)
185-188 F4.2 --- E_C Upper CI of C
190-193 F4.2 --- e_C Lower CI of C
195-198 F4.2 --- N Nitrogen abundance (7)
200-203 F4.2 --- E_N Upper CI of N
205-208 F4.2 --- e_N Lower CI of N
210-212 A3 --- fnote Note on quality (8)
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Note (2): Wind turbulence as fraction of the terminal velocity
Note (3): The interclump density contrast is defined as fic = rhoic/rhoavg,
where rho_ic is the density of the interclump medium, and rho_avg the
average density of the stellar wind
Note (4): The velocity-porosity is defined as fvel=fvol/(1+fvol), where
fvol is the volume filling fraction of the clumps
Note (5): Onset velocity of the clumping as a fraction of the terminal velocity.
Note (6): The carbon abundance is expressed in fractional number density and
defined as: C=log10(nC/nH)+12, with n_C and n_H the number density of
carbon and hydrogen, respectively.
Note (7): The nitrogen abundance is expressed in fractional number density and
defined as: N=log10(nN/nH)+12, with n_N and n_H the number density of
nitrogen and hydrogen, respectively.
Note (8): Note as follows:
b = Run with 14 free parameters. Values for the helium and oxygen surface
abundance can be found in Table 6 (in the paper)
c = Formal uncertainties assuming a Teff=50kK. In reality uncertainties
on all parameters are larger due to the uncertain Teff
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Source Name of the source (G1)
8- 11 F4.2 [Lsun] logL Logarithmic luminosity in terms of solar
13- 16 F4.2 [Lsun] E_logL Upper CI of logL
18- 21 F4.2 [Lsun] e_logL Lower CI of logL
23- 27 I5 K Teff Effective temperature
29- 32 I4 K E_Teff Upper CI of Teff
34- 37 I4 K e_Teff Lower CI of Teff
39- 42 F4.2 [cm/s2] logg logarithmic surface gravity
44- 47 F4.2 [cm/s2] E_logg Upper CI of logg
49- 52 F4.2 [cm/s2] e_logg Lower CI of logg
54- 57 F4.1 Rsun R Stellar radius
59- 61 F3.1 Rsun E_R Upper CI of R
63- 65 F3.1 Rsun e_R Lower CI of R
67- 71 F5.2 Msun/yr Mdot Logarithmic mass-loss rate
73- 76 F4.2 Msun/yr E_Mdot Upper CI of Mdot
78- 81 F4.2 Msun/yr e_Mdot Lower CI of Mdot
83- 86 I4 km/s vinf Terminal outflow velocity
88- 91 I4 km/s E_vinf Upper CI of vinf
93- 96 I4 km/s e_vinf Lower CI of vinf
98- 99 I2 --- fclump Clumping factor
101-102 I2 --- E_fclump Upper CI of fclump
104-105 I2 --- e_fclump Lower CI of fclump
107-110 F4.2 --- beta Wind acceleration parameter beta
112-115 F4.2 --- E_beta Upper CI of beta
117-120 F4.2 --- e_beta Lower CI of beta
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Byte-by-byte Description of file: tablei1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Name of the source (G1)
8- 20 A13 --- SpType Spectral type (2)
22- 24 I3 Msun Mini Initial mass
26- 27 I2 Msun E_Mini Upper CI on Mini
29- 30 I2 Msun e_Mini Lower CI on Mini
32- 34 I3 Msun Mevol Current evolutionary mass
36- 37 I2 Msun E_Mevol Upper CI on Mevol
39- 40 I2 Msun e_Mevol Lower CI on Mevol
42- 44 I3 Msun Mspec Current spectroscopic mass
46- 49 I4 Msun E_Mspec Upper CI on Mspec
51- 53 I3 Msun e_Mspec Lower CI on Mspec
55- 58 F4.2 Myr age Current stellar age
60- 63 F4.2 Myr E_age Upper CI on age
65- 68 F4.2 Myr e_age Lower CI on age
70- 74 F5.2 ph/s Q0 Logarithmic H-I ionising luminosity (3)
76- 80 F5.2 ph/s Q1 Logarithmic He-I ionising luminosity (3)
82- 86 F5.2 ph/s Q2 Logarithmic He-II ionising luminosity (3)
88- 91 F4.2 Lsun L136 Logarithmic ionising luminosity (4)
93- 96 F4.2 --- Gamma Eddington factor for electron scattering
98-101 F4.2 --- E_Gamma Upper CI on Gamma
103-106 F4.2 --- e_Gamma Lower CI on Gamma
108-109 I2 K Tiron Effective temperature from iron lines
111-113 A3 --- fnote Note on quality (5)
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Note (2): Spectral types from Crowther et al. (2016MNRAS.458..624C 2016MNRAS.458..624C, WN5h stars)
and Caballero-Nieves (in prep., all other stars).
Note (3): by convention Qx=qx*4*pi*R2, with qx the ionising
radiation (number of photons) per unit surface area per second and x
= 0, 1 or 2 for H-I, He-I or He-II ionising flux, respectively.
Note (4): This quantity is expressed as L136=log10(LE136/L☉), with
LE136 the luminosity of photons with an energy >13.6eV
Note (5): Note as follows:
c = Formal uncertainties assuming a Teff=50kK. In reality uncertainties
on all parameters are larger due to the uncertain Teff.
d = No good fit obtained to iron pseudo-continuum; assumed value closest
to Bestenlehner et al. (2014A&A...570A..38B 2014A&A...570A..38B) for UV normalisation.
e = Cross-contamination of the spectrum as a result of crowding (as in
Bestenlehner et al., 2014A&A...570A..38B 2014A&A...570A..38B)
f = Severe cross-contamination of the spectrum as a result of crowding:
R136a5 consists of H19 and H26
g = Potential spectroscopic binary
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Byte-by-byte Description of file: tablei2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Name of the source (G1)
8- 11 F4.2 [Lsun] logL Logarithmic luminosity in terms of solar
13- 16 F4.2 [Lsun] E_logL Upper CI of logL
18- 21 F4.2 [Lsun] e_logL Lower CI of logL
23- 27 I5 K Teff Effective temperature
29- 33 I5 K E_Teff Upper CI of Teff
35- 39 I5 K e_Teff Lower CI of Teff
42- 45 F4.2 [cm/s2] logg logarithmic surface gravity
47- 50 F4.2 [cm/s2] E_logg Upper CI of logg
52- 55 F4.2 [cm/s2] e_logg Lower CI of logg
57- 60 F4.1 Rsun R Stellar radius
62- 64 F3.1 Rsun E_R Upper CI of R
66- 68 F3.1 Rsun e_R Lower CI of R
70- 74 F5.2 Msun/yr Mdot Logarithmic mass-loss rate
76- 79 F4.2 Msun/yr E_Mdot Upper CI of Mdot
81- 84 F4.2 Msun/yr e_Mdot Lower CI of Mdot
86- 89 F4.2 --- beta ? Wind acceleration parameter beta
91- 94 F4.2 --- E_beta ? Upper CI of beta
96- 99 F4.2 --- e_beta ? Lower CI of beta
101-103 I3 km/s vsini Projected rotational broadening
105-107 I3 km/s E_vsini Upper CI of vsini
109-111 I3 km/s e_vsini Lower CI of vsini
113-116 F4.2 --- xHe Helium surface abundance (2)
118-121 F4.2 --- E_xHe Upper CI of xHe (2)
123-126 F4.2 --- e_xHe Lower CI of xHe (2)
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Note (2): Helium surface abundance given in fractional number density, that is
xHe = nHe/nH, with n_He and n_H the number density of helium and
hydrogen, respectively.
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Global notes:
Note (G1): Identifications starting with H are from Hunter et al.
(1995ApJ...448..179H 1995ApJ...448..179H, Cat. J/ApJ/448/179, will be [HSH95] NNNN in Simbad),
those starting with R136 are from Weigelt & Baier (1985A&A...150L..18W 1985A&A...150L..18W),
RMC 136aN in Simbad.
Acknowledgements:
Sarah Brands, s.a.brands(at)uva.nl
(End) Patricia Vannier [CDS] 21-Apr-2022