J/A+A/634/A18 Be and Bn stars Balmer discontinuity (Cochetti+, 2020)
Be and Bn stars: Balmer discontinuity and stellar-class relationship.
Cochetti Y.R., Zorec J., Cidale L.S., Arias M.L., Aidelman Y., Torres A.F.,
Fremat Y., Granada A.
<Astron. Astrophys., 634, A18 (2020)>
=2020A&A...634A..18C 2020A&A...634A..18C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Be
Keywords: circumstellar matter - stars: emission-line, Be -
stars: fundamental parameters
Abstract:
A significant number of Be stars show a second Balmer discontinuity
(sBD) attributed to an extended circumstellar envelope (CE). The fast
rotational velocity of Be stars undoubtedly plays a significant role
in the formation of the CE. However, Bn stars, which are also B-type
rapidly rotating stars, do not all present clear evidence of being
surrounded by circumstellar material.
We aim to characterize the populations of Be and Bn stars, and discuss
the appearance of the sBD as a function of the stellar parameters. We
expect to find new indices characterizing the properties of CEs in Be
stars and properties relating Be and Bn stars.
We obtained low- and high-resolution spectra of a sample of Be and Bn
stars, derived stellar parameters, characterized the sBD, and measured
the emission in the Hα line. Results. Correlations of the aspect
and intensity of the sBD and the emission in the Hα line with
the stellar parameters and the Vsini are presented. Some Bn stars
exhibit the sBD in absorption, which may indicate the presence of
rather dense CEs. Six Bn stars show emission in the Hα line, so
they are reclassified as Be stars. The sBD in emission appears in Be
stars with Vsini≤250km/s, and in absorption in both Be and Bn stars
with Vsini≥50km/s Low-mass Be and Bn stars share the same region in
the Hertzsprung-Russell diagram. The distributions of rotational to
critical velocity ratios of Be and Bn stars corresponding to the
current stellar evolutionary stage are similar, while distributions
inferred for the zero-age main sequence have different skewness.
We found emission in the Hα line and signs of a CE in some Bn
stars, which motivated us to think that Bn and Be stars probably
belong to the same population. It should be noted that some of the
most massive Bn stars could display the Be phenomenon at any time.
The similarities found among Be and Bn stars deserve to be more deeply
pursued.
Description:
The sample consists of 67 Be and 61 Bn Galactic stars, listed in the
BSC (Hoffleit & Jaschek, 1982, Cat. V/50). Low- and high-resolution
spectroscopic observationsfor the sample stars were obtained at the
Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. In
addition, we obtained Hα spectra for some Be stars from the Be
Star Spectra database (BeSS; Neiner et al., 2011AJ....142..149N 2011AJ....142..149N) or
the Spectroscopic Be Stars Atlas
(http://www.astrosurf.com/buil/us/becat.htm).
Observational characteristics of a sample of Be and Bn stars based on
the behavior of their sBD, the Hα emission intensity, and their
correlation with the stellar parameters are presented.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 90 67 Observed Be stars
tablea2.dat 91 61 *Observed Bn stars
tablea3.dat 92 73 Observed BCD and apparent parameters of Be stars
tablea4.dat 92 55 Observed BCD and apparent parameters of Bn stars
tablea5.dat 61 73 Derived apparent fundamental parameters of Be stars
tablea6.dat 61 55 Derived apparent fundamental parameters of Bn stars
tablea7.dat 36 71 Halpha line emission equivalent widths and
fluxes of Be stars
tablea8.dat 80 73 Parent nonrotating counterpart (pnrc)
fundamental parameters of Be stars
tablea9.dat 80 55 Parent nonrotating counterpart (pnrc)
fundamental parameters of Bn stars
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Note on tablea2.dat: Six Bn stars show emission in the Hα line, so they
are reclassified as Be stars, HD 42327, HD 43445, HD 31209, HD 165910,
HD 171623 and HD 225132.
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See also:
V/50 : Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
11- 12 I2 h RAh Right ascension (ICRS, J2000.0)
14- 15 I2 min RAm Right ascension (ICRS, J2000.0)
17- 24 F8.5 s RAs Right ascension (ICRS, J2000.0)
26 A1 --- DE- Declination sign (ICRS, J2000.0)
27- 28 I2 deg DEd Declination (ICRS, J2000.0)
30- 31 I2 arcmin DEm Declination (ICRS, J2000.0)
33- 39 F7.4 arcsec DEs Declination (J2000.0)
41- 44 F4.2 mag Vmag V magnitude
46- 55 A10 "date" Obs.datel1 Low-resolution observation dates
56 A1 --- --- [/]
57- 66 A10 "date" Obs.datel2 Low-resolution observation dates
68- 77 A10 "date" Obs.dateh1 High-resolution observation dates
78 A1 --- n_Obs.dateh1 [ab] Note on Obs.dateh1 (1)
79 A1 --- --- [/]
80- 89 A10 "date" Obs.dateh2 High-resolution observation dates
90 A1 --- n_Obs.dateh2 [ab] Note on Obs.dateh2 (1)
91 A1 --- Flag [*] Flag for Bn stars reclassified as
Be stars
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Note (1): All the spectra were obtained in CASLEO, with the exception of
those denoted with
a = BeSS (Neiner et al. 2011AJ....142..149N 2011AJ....142..149N)
b = the Spectroscopic Be Stars Atlas
(http://www.astrosurf.com/buil/us/becat.htm)
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Byte-by-byte Description of file: tablea3.dat tablea4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
12- 15 F4.2 --- D* BCD quantity D* (1)
17- 18 I2 --- lambda1 BCD quantity λ1
20- 29 A10 --- SpType Spectral type
31- 35 F5.2 --- d1 ? BCD quantity d (1)
36 A1 --- n_d1 [ea] Note on d1 (2)
37 A1 --- --- [/]
38- 42 F5.2 --- d2 ? Second measurement of BCD quantity d (1)
43 A1 --- n_d2 [ea] Note on d2 (2)
45- 48 F4.2 mag E(B-V) Reddening
50- 54 F5.2 mag VMAG Absolute V magnitude
56- 59 F4.2 mag e_VMAG rms uncertainty on VMAG
61- 65 I5 K Teff Effective temperature, Teff(lambda1,D*)
67- 70 I4 K e_Teff rms uncertainty on Teff
72- 76 F5.3 [Lsun] logL Luminosity
78- 82 F5.3 [Lsun] e_logL rms uncertainty on logL
84- 86 I3 km/s vsini ? Rotational velocity
88- 89 I2 km/s e_vsini ? rms uncertainty on vsini
91- 92 I2 --- r_vsini Reference for vsini (3)
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Note (1): D* characterizes the photosphere of the rotationally deformed stellar
hemisphere projected toward the observer and d is produced by the
circumstellar gaseous environment of these objects)
We refer then to a total Balmer discontinuity (BD) written as D=D*+d.
lambda1 is the mean spectral position of the Balmer jump, relative to
λ3700Å.
Note (2): Note as follows:
a = absorption
e = emission
Note (3): References as follows:
1 = Zorec et al. (2005A&A...441..235Z 2005A&A...441..235Z)
2 = Levenhagen & Leister (2006, Cat. J/MNRAS/371/252)
3 = Zorec & Royer (2012, Cat. J/A+A/537/A120)
4 = Fremat et al. (2005, Cat. J/A+A/440/305)
5 = Chauville et al. (2001, Cat. J/A+A/378/861)
6 = Wolff et al. (1982ApJ...252..322W 1982ApJ...252..322W)
7 = Abt et al. (2002, Cat. J/ApJ/573/359)
8 = Yudin (2001, Cat. J/A+A/368/912)
9 = Slettebak (1982ApJS...50...55S 1982ApJS...50...55S)
10 = Uesugi & Fukuda (1982, Cat. III/63)
11 = this work
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Byte-by-byte Description of file: tablea5.dat tablea6.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name
12- 16 F5.2 Msun Mass Stellar mass
18- 21 F4.2 Msun e_Mass rms uncertainty on Mass
23- 26 F4.2 [cm/s2] logg Surface gravity
28- 31 F4.2 [cm/s2] e_logg rms uncertainty on logg
33- 37 F5.2 Rsun R Stellar radius
39- 42 F4.2 Rsun e_R rms uncertainty on Radius
44- 46 I3 km/s Vc Equatorial critical velocity
48- 49 I2 km/s e_Vc rms uncertainty on Vc
51- 55 F5.3 --- t/tMS Stellar age in terms of the fractional age tMS
57- 61 F5.3 --- e_t/tMS rms uncertainty on t/tMS
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Byte-by-byte Description of file: tablea7.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name
12- 16 F5.2 0.1nm We Equivalent width of the emission superimposed
to the underlying photospheric absorption
line profile
19- 23 F5.2 0.1nm W Total equivalent width
25- 30 F6.3 10+12W/m2 FHa Flux in the Halpha line emission
(109erg/cm2/s)
32- 36 F5.2 --- d BCD quantity d
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Byte-by-byte Description of file: tablea8.dat tablea9.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
12- 16 I5 K Teff Effective temperature
18- 21 I4 K e_Teff rms uncertainty on Teff
23- 27 F5.3 [Lsun] logL Stellar luminosity
29- 33 F5.3 [Lsun] e_logL rms uncertainty on logL
35- 38 F4.2 [cm/s2] logg Surface gravity
40- 43 F4.2 [cm/s2] e_logg rms uncertainty on logg
45- 49 F5.2 Msun Mass Stellar mass
51- 54 F4.2 Msun e_Mass rms uncertainty on Mass
56- 58 I3 km/s vsini ? Rotational velocity
60- 61 I2 km/s e_vsini ? rms uncertainty on vsini
63- 65 I3 km/s Vc Equatorial critical velocity
67- 68 I2 km/s e_Vc rms uncertainty on Vc
70- 74 F5.3 --- t/tMS Stellar age in terms of the fractional age tMS
76- 80 F5.3 --- e_t/tMS rms uncertainty on t/tMS
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 27-Apr-2020