J/A+A/595/A132 Be star rotational velocities distribution (Zorec+, 2016)
Critical study of the distribution of rotational velocities of Be stars.
I: Deconvolution methods, effects due to gravity darkening, macro-turbulence
and binarity.
Zorec J., Fremat Y., Domiciano de Souza A., Royer F., Cidale L.,
Hubert A.-M., Semaan T., Martayan C., Cochetti Y.R., Arias M.L.,
Aidelman Y., Stee P.
<Astron. Astrophys. 595, A132 (2016)>
=2016A&A...595A.132Z 2016A&A...595A.132Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Be ; Rotational velocities
Keywords: stars: emission-line, Be - stars: rotation
Abstract:
Among intermediate-mass and massive stars, Be stars are the fastest
rotators in the main sequence (MS) and, as such, these stars are a
cornerstone to validate models of structure and evolution of rotating
stars. Several phenomena, however, induce under- or overestimations
either of their apparent Vsini, or true velocity V.
In the present contribution we aim at obtaining distributions of true
rotational velocities corrected for systematic effects induced by the
rapid rotation itself, macroturbulent velocities, and binarity.
We study a set of 233 Be stars by assuming they have inclination
angles distributed at random. We critically discuss the methods of
Cranmer and Lucy-Richardson, which enable us to transform a
distribution of projected velocities into another distribution of true
rotational velocities, where the gravitational darkening effect on the
Vsini parameter is considered in different ways. We conclude that
iterative algorithm by Lucy-Richardson responds at best to the
purposes of the present work, but it requires a thorough determination
of the stellar fundamental parameters. We conclude that once the mode
of ratios of the true velocities of Be stars attains the value
V/Vc∼0.77 in the main-sequence (MS) evolutionary phase, it remains
unchanged up to the end of the MS lifespan. The statistical
corrections found on the distribution of ratios V/Vc for
overestimations of Vsini due to macroturbulent motions and binarity,
produce a shift of this distribution toward lower values of V/Vc when
Be stars in all MS evolutionary stages are considered together. The
mode of the final distribution obtained is at V/Vc∼0.65. This
distribution has a nearly symmetric distribution and shows that the Be
phenomenon is characterized by a wide range of true velocity ratios
0.3<V/Vc<0.95. It thus suggests that the probability that Be stars
are critical rotators is extremely low.
The corrections attempted in the present work represent an initial
step to infer indications about the nature of the Be-star surface
rotation that will be studied in the second paper of this series.
Description:
Table 1 contains apparent fundamental parameters of the 233 Galactic
Be stars. For each Be star is given the HD number, the effective
temperature, effective surface gravity and bolometric luminosity. They
correspond to the parameters of a plan parallel model of stellar
atmosphere that fits the energy distribution of the stellar apparent
hemisphere rotationally deformed. In Table 1 are also given the color
excess E(B-V) and the vsini rotation parameter determined with model
atmospheres of rigidly rotating stars. For each parameter is given the
1sigma uncertainty. In the notes are given the authors that produced
some reported the data or the methods used to obtain the data.
Table 4 contains parent-non-rotating-counterpart fundamental
parameters of 233 Be stars: effective temperature, effective surface
gravity, bolometric luminosity in solar units, stellar mass in solar
units, fractional main-sequence stellar age, pnrc-apparent rotational
velocity, critical velocity, ratio of centrifugal-force to gravity in
the equator, inclination angle of the rotational axis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 67 233 Apparent fundamental parameters of 233 Be stars
table4.dat 88 233 Parent-non-rotating-counterpart fundamental
parameters of 233 Be stars
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See also:
J/A+A/378/861 : Spectroscopy of Be stars (Chauville+, 2001)
J/A+A/440/305 : Fast-rotating B stars fundamental parameters (Fremat+, 2005)
J/A+A/451/1053 : Fundamental parameters of Be stars (Fremat+, 2006)
J/MNRAS/371/252 : Southern B and Be stars (Levenhagen+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HD HD identification number of star
8- 12 I5 K Teff Effective temperature
14- 17 I4 K s_Teff 1σ dispersion of Teff
19- 22 F4.2 [cm/s2] logg log_10 of effective gravity
24- 27 F4.2 [cm/s2] s_logg 1σ dispersion in logg
29- 33 F5.3 [Lsun] logL log_10 of bolometric luminosity
35- 39 F5.3 [Lsun] s_logL 1σ dispersion in logL
41- 45 F5.3 mag E(B-V) (B-V) color excess
47- 51 F5.3 mag s_E(B-V) 1σ dispersion of E(B-V)
53- 55 I3 km/s vsini apparent rotational velocity
57- 58 I2 km/s s_vsini 1σ dispersion of vsini
60- 67 A8 --- Notes Notes (1)
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Note (1): Notes as follows
1 = stars studied in Chauville et al., 2001A&A...378..861C 2001A&A...378..861C,
Cat. J/A+A/378/861, Fremat et al., 2005A&A...440..305F 2005A&A...440..305F,
Cat. J/A+A/440/305, Zorec et al 2005A&A...441..235Z 2005A&A...441..235Z
2 = stars studied in Levenhagen & Leister 2006MNRAS.371..252L 2006MNRAS.371..252L,
Cat, J/MNRAS/371/252
3 = stars studied in Fremat 2006A&A...451.1053F 2006A&A...451.1053F, Cat. J/A+A/451/1053
4 = stars with new BCD observations coch14
f = stars with integrated fluxes
d = stars with spectroscopic distances
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HD HD identification number of star
8- 12 I5 K Teff pnrc effective temperature (1)
14- 17 I4 K s_Teff 1σ dispersion of pnrc Teff
19- 22 F4.2 [cm/s2] logg log_10 of pnrc effective gravity
24- 27 F4.2 [cm/s2] s_logg 1σ dispersion in log_logg
29- 33 F5.3 [Lsun] logL log_10 of pnrc bolometric luminosity
35- 39 F5.3 [Lsun] s_logL 1σ dispersion in logL
41- 44 F4.1 Msun M Stellar mass
46- 48 F3.1 Msun e_M 1σ rms uncertainty of M
50- 53 F4.2 --- t/tMS Fractional stellar MS age; tMS time spent
by the star in Main-sequence
55- 58 F4.2 --- e_t/tMS 1σ rms uncertainty of t/tMS
60- 62 I3 km/s vsini pnrc rotational velocity (1)
64- 65 I2 km/s e_vsini 1σ rms uncertainty of vsini
67- 69 I3 km/s Vc pnrc critical velocity (1)
71- 72 I2 km/s e_Vc 1σ rms uncertainty of Vc
74- 77 F4.2 ---- eta Ratio of centrifugal-force to gravity
79- 82 F4.2 ---- e_eta 1σ rms uncertainty of eta
84- 85 I2 deg i Inclination angle
87- 88 I2 deg e_i 1σ rms uncertainty of i
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Note (1): pnrc = parent-non-rotating-counterpart
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Acknowledgements:
Jean Zorec, zorec(at)iap.fr
(End) Jean Zorec [IAP, France], Patricia Vannier [CDS] 27-Jun-2016