J/A+A/603/A56 Stellar parameters and assumed wind parameters (Cazorla+, 2017)
Chemical abundances of fast-rotating massive stars.
I. Description of the methods and individual results.
Cazorla C., Morel T., Naze Y., Rauw G., Semaan T., Daflon S., Oey S.
<Astron. Astrophys. 603, A56 (2017)>
=2017A&A...603A..56C 2017A&A...603A..56C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, OB ; Radial velocities ; Rotational velocities ;
Effective temperatures ; Abundances
Keywords: stars: abundances - stars: early-type -
stars: fundamental parameters - stars: massive - stars: rotation
Abstract:
Recent observations have challenged our understanding of rotational
mixing in massive stars by revealing a population of fast-rotating
objects with apparently normal surface nitrogen abundances. However,
several questions have arisen because of a number of issues (e.g.,
presence of numerous upper limits for the nitrogen abundance, unknown
multiplicity status, mix of stars with different physical properties
such as their mass and evolutionary state that are known to control
the amount of rotational mixing), rendering a re-investigation
necessary.
We have carefully selected a large sample of bright, fast-rotating
early-type stars of our Galaxy (40 objects with spectral types between
B0.5 and O4). Their high-quality, high-resolution optical spectra were
then analysed with the stellar atmosphere modelling codes
DETAIL/SURFACE or CMFGEN, depending on the temperature of the target.
Several internal and external checks were performed to validate our
methods, notably comparing our results with literature data for some
well-known objects, studying the effect of gravity darkening, or
confronting the results provided by the two codes for stars amenable
to both analyses. Furthermore, we have studied the radial velocities
of the stars to assess their binarity.
This first part of our study presents our methods and provides the
derived stellar parameters, He, CNO abundances and the multiplicity
status of every star of the sample. It is the first time that He and
CNO abundances of such a large number of Galactic massive fast
rotators are determined in a homogeneous way.
Description:
Stellar parameters derived for the stars in our sample and assumed
wind parameters for our hotter stars.
Because macroturbulent velocities cannot be determined reliably for
fast rotators (Sect. 4.2), all values in column 6 are upper limits.
Column 7 provides the multiplicity status (see Sect. 4.1 for the
classification criterion and Appendix C for the RV studies of each
individual object). The runaway status is based on literature studies
(references are given on a star-to-star basis in Appendix C). Columns
15, 16, and 17 of the table presenting the results for the hotter
stars list the assumed wind parameters. For stars with the lowest
temperatures (typically B0.5 stars), the carbon abundance cannot be
firmly determined due to the weakness of the CIII lines at these
temperatures. Besides, NII lines may also be very weak for the
hottest stars studied with DETAIL/SURFACE. In these cases, we provide
upper limits for both carbon and nitrogen abundances. They correspond
to predicted lines becoming detectable, i.e., having a depth
significantly exceeding the local noise. Similarly, CMFGEN fits may
converge towards very high or very low CNO abundances. In both cases,
the upper or lower limits were determined from the chi2 curves and
correspond to the limit of their flat minimum. Since the CNO
abundances are measured relative to the hydrogen content (assumed to
be constant in our study), a correction should in principle be applied
to the CNO abundances of stars that exhibit a very high helium
abundance (and therefore have a reduced hydrogen abundance). However,
we found this correction to be negligible (≲0.1dex) even for the
most He-rich stars. The 1σ errors on the parameters are given in
dedicated columns.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cool.dat 155 17 Cooler stars stellar parameters (table F2, part 1)
hot.dat 165 23 Hotter stars stellar parameters and assumed wind
parameters (table F2, part 2)
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Byte-by-byte Description of file: cool.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10 I1 --- n_Name [1/2]? Note on Name (1)
12- 14 I3 km/s vsini Projected rotational velocity
16- 17 I2 km/s e_vsini Error on vsini
19 A1 --- l_vmac Upper limit sign for vmac
21- 23 I3 km/s vmac Macroturbulence velocity
25- 36 A12 --- mult Multiplicity from spectroscopy
38- 40 A3 --- runStat [Yes No] Runaway?
42- 46 I5 K Teff Effective temperature
48- 51 I4 K e_Teff Error on Teff
53- 56 F4.2 [cm/s2] logg Surface gravity
58- 61 F4.2 [cm/s2] e_logg Error on logg
63- 66 F4.2 [cm/s2] loggC Surface gravity corrected for centrifuge
forces
68- 71 F4.2 [cm/s2] e_loggC Error on loggC
73- 77 F5.3 --- Y Helium abundance
79- 83 F5.3 --- e_Y Error on Y
85 A1 --- l_logE(C) Lower/upper limit in logE(C)
87- 90 F4.2 --- logE(C) ? Carbon abundance
92- 95 F4.2 --- e_logE(C) Error on logE(C)
97 A1 --- l_logE(N) Lower/upper limit in logE(N)
99-102 F4.2 --- logE(N) Nitrogen abundance
104-107 F4.2 --- e_logE(N) Error on logE(N)
109 A1 --- l_logE(O1) Lower/upper limit in logE(O) in 4060-4082Å
111-114 F4.2 --- logE(O1) ? Oxygen abundance in 4060-4082Å
116-119 F4.2 --- logE(O2) Oxygen abundance in 4691-4709Å
121-124 F4.2 --- logE(O) Adopted oxygen abundance
126-129 F4.2 --- e_logE(O) Error on logE(O)
131 A1 --- l_[N/C] Lower/upper limit in [N/C]
133-137 F5.2 --- [N/C] ? N/C abundance ratio
139-142 F4.2 --- e_[N/C] Error on [N/C]
144 A1 --- l_[N/O] Lower/upper limit in [N/O]
146-150 F5.2 --- [N/O] N/O abundance ratio
152-155 F4.2 --- e_[N/O] Error on [N/O]
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Note (1): Note on Name ars follows:
1 = because the UCLES spectrum only covers the wavelength range ∼4350-6800Å,
neither Hε, Hδ, Hγ, He I 4026, nor the C and O lines
in the 4060-4082Å region were used. In order to check the reliability
of our results, we have determined the atmospheric parameters of HD 172367
(whose spectral type is similar to HD 53755) considering either only one
(Hβ), or four (Hε, Hδ, Hγ, Hβ) Balmer lines.
No significant differences were found between the two sets of results,
ensuring that our parameter derivation for HD 53755 is secure.
2 = stars studied with both DETAIL/SURFACE and CMFGEN.
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Byte-by-byte Description of file: hot.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10 I1 --- n_Name [1]? Note on Name (1)
12- 14 I3 km/s vsini Projected rotational velocity
16- 17 I2 km/s e_vsini Error on vsini
19 A1 --- l_vmac Upper limit sign for vmac
21- 23 I3 km/s vmac Macroturbulence velocity
25- 36 A12 --- mult Multiplicity from spectroscopy
38- 40 A3 --- runStat Runaway?
42- 46 I5 K Teff Effective temperature
48- 51 I4 K e_Teff Error on Teff
53- 56 F4.2 [cm/s2] logg Surface gravity
58- 61 F4.2 [cm/s2] e_logg Error on logg
63- 66 F4.2 [cm/s2] loggC Surface gravity corrected for centrifuge
forces
68- 71 F4.2 [cm/s2] e_loggC Error on loggC
73- 76 F4.1 [Msun/yr] logdM/dt Mass-loss rate
78- 81 I4 km/s vinf Terminal velocity
83- 86 F4.2 --- beta Wind beta parameter
88- 92 F5.3 --- Y Helium abundance
94- 98 F5.3 --- e_Y Error on y
100-101 A2 --- l_logE(C) [<≥ ] Lower/upper limit in logE(C)
103-106 F4.2 --- logE(C) Carbon abundance
108-111 F4.2 --- e_logE(C) Error on logE(C)
113-114 A2 --- l_logE(N) [<≥ ] Lower/upper limit in logE(N)
116-119 F4.2 --- logE(N) Nitrogen abundance
121-124 F4.2 --- e_logE(N) Error on logE(N)
126-127 A2 --- l_logE(O) [<≥ ] Lower/upper limit in logE(O)
129-132 F4.2 --- logE(O) Oxygen abundance
134-137 F4.2 --- e_logE(O) Error on logE(O)
139-140 A2 --- l_[N/C] [<≥ ] Lower/upper limit in [N/C]
142-146 F5.2 --- [N/C] N/C abundance ratio
148-151 F4.2 --- e_[N/C] Error on [N/C] (2)
153-154 A2 --- l_[N/O] [<≥ ] Lower/upper limit in [N/O]
156-160 F5.2 --- [N/O] ? N/O abundance ratio
162-165 F4.2 --- e_[N/O] ? Error on [N/O] (2)
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Note (1): Note on Name as follows:
1 = atmospheric parameters and surface abundances must be considered with
caution, as they were derived from a low S/N spectrum that only ranges
from 4075 to 4920Å (i.e., with fewer diagnostic lines).
Note (2): quadratic sum of the CNO abundance uncertainties.
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Acknowledgements:
Constantin Cazorla, cazorla(at)astro.ulg.ac.be
(End) Constantin Cazorla [Belgium], Patricia Vannier [CDS] 16-Mar-2017