J/ApJ/948/34 Galactic Be star inclination angles (Sigut+, 2023)
Comparing Be star inclination angles determined from Hα fitting and
gravitational darkening.
Sigut T.A.A., Ghafourian N.R.
<Astrophys. J., 948, 34 (2023)>
=2023ApJ...948...34S 2023ApJ...948...34S
ADC_Keywords: Stars, Be; Rotational velocities; Spectral types;
Photometry, H-alpha; Spectra, optical
Keywords: Open star clusters ; Stellar rotation ; Be stars ; Star formation ;
Early-type stars ; Fundamental parameters of stars ;
Circumstellar disks
Abstract:
Using a sample of 92 Galactic Be stars, we compare inclination angles
(the angle between a star's rotation axis and the line of sight)
determined from Hα emission-line profile fitting to those
determined by the spectroscopic signature of gravitational darkening.
We find good agreement: 70% of the sample (64 out of 92 stars) is
consistent with zero difference between the two methods using 1σ
errors, and there is a strong linear correlation coefficient between
the two methods of r=+0.63±0.05. There is some evidence that the
Hα profile fitting method overestimates the inclination angle
for i≲25°, perhaps due to the neglect of incoherent electron
scattering on the Hα line widths, while the gravitational
darkening method underestimates the inclination angle for i≳70°,
perhaps due to the neglect of disk radiative transfer effects on the
optical spectrum. Overall, it is demonstrated that a single Hα
spectrum of modest resolution and SNR can be used to extract a useful
estimate for the inclination angle of an individual Be star. This
allows equatorial rotation velocities for individual Be stars to be
derived from vsini measurements and will allow Be stars to be used
to search for correlated spin axes in young, open clusters if unbiased
(with respect to inclination) samples of Be stars are used.
Description:
Of the 233 Be stars considered by Zorec+ 2016, J/A+A/595/A132, we have
obtained a sample of 92 stars with available Hα spectra, 58 from
the BeSS spectral database (http://basebe.obspm.fr/basebe/) and
34 from the John S. Hall telescope at Lowell Observatory. The Hall
spectra have and SNR of ∼102 or better, while the spectra from BeSS
are a heterogeneous group with a range of SNRs and resolutions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 67 92 Be star sample
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See also:
J/ApJS/99/135 : Rotation and Spectral Peculiarities (Abt+ 1995)
J/A+A/440/305 : Fundamental param. of fast-rotating B stars (Fremat+, 2005)
J/A+A/451/1053 : Fundamental parameters of Be stars (Fremat+, 2006)
J/A+A/459/137 : Bright Be shell stars (Rivnius+, 2006)
J/ApJ/814/159 : Hα interferometric visibilities of o Aqr (Sigut+, 2015)
J/A+A/595/A132 : Be star rotational velocities distribution (Zorec+, 2016)
J/A+A/618/A109 : Seismic global parameters of 372 KIC (Mosser+, 2018)
J/MNRAS/488/572 : Bayesian hierarchical inferred incl. (Kuszlewicz+, 2019)
J/ApJ/903/99 : Stellar spins in the open cluster NGC 2516 (Healy+, 2020)
J/A+A/645/A124 : Inclinations for RGBs from Kepler (Gehan+, 2021)
J/ApJ/923/23 : Stellar spins in the Pleiades, Praesepe & M35 (Healy+, 2021)
http://basebe.obspm.fr/basebe/ : Be Star Spectra database (BeSS)
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 [144/224686] HD catalog identifier
8- 18 A11 --- Name Common star name
20- 25 A6 --- SpT Spectral Type from SIMBAD
27- 28 I2 deg iHa [12/88] Stellar inclination, Hα line
fitting
30- 31 I2 deg e_iHa [5/17] Uncertainty (1σ) in iHa
33- 34 I2 deg iGD [13/89] Stellar inclination, gravitational
darkening [i] (1)
36- 37 I2 deg e_iGD [7/22] Uncertainty (1σ) in iGD (1)
39- 43 F5.2 --- Shell [1/12.02] Shell parameter, this work (2)
45- 48 F4.2 --- V/R [1/1.2] Ratio, V(iolet) and R(ed) emission peak
fluxes, this work
50- 52 I3 km/s vsini [40/603] Projected rotational velocity (1)
54- 55 I2 km/s e_vsini [3/55] Uncertainty (1σ) in vsini (1)
57- 60 A4 --- Source Source (3)
62- 67 A6 --- Notes Note(s) (4)
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Note (1): Inclinations derived from gravitational darkening and projected
rotational velocities taken from Table 4, Zorec+ 2016, J/A+A/595/A132
Note (2): The shell parameter is the ratio of the average of the V(iolet) and
R(ed) emission peak fluxes divided by the line center flux.
Note (3): Source as follows:
BeSS = BeSS spectral database, Operated at LESIA, Observatoire de Meudon,
France: http://basebe.obspm.fr/
Hall = from the John S. Hall telescope at Lowell Observatory; see
Silaj+ 2014ApJ...795...82S 2014ApJ...795...82S
Note (4): Notes for each star as follows:
25 = The R=25000 resolution library profiles were used;
N = the observed profile was noisy;
T = significant telluric features in the observed profile.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-May-2025