J/ApJ/921/5 TESS observations of Be stars (Balona+, 2021)
TESS observations of Be stars: general characteristics and the impulsive
magnetic rotator model.
Balona L.A., Ozuyar D.
<Astrophys. J., 921, 5 (2021)>
=2021ApJ...921....5B 2021ApJ...921....5B
ADC_Keywords: Stars, Be; Stars, variable; Rotational velocities; Photometry;
Optical; Effective temperatures
Keywords: Be stars ; Early-type emission stars ; Emission line stars ;
B(e) stars ; Stellar rotation ; Stellar properties ; Starspots
Abstract:
Evidence of rotational light modulation in 30%-40% of normal B stars
is presented, suggesting the presence of starspots and photospheric
activity. On this basis, we propose that mass loss in Be stars is a
result of magnetic reconnection coupled with rapid but not necessarily
near-critical rotation. The ejected matter is trapped at two
diametrically opposed locations where the magnetic and geometric
equators intersect. Nonradial pulsation plays no role in the mass loss
and in the short-period light and line profile variations, though Be
stars may pulsate as SPB or β Cep variables. The model allows
many of the major characteristics of Be stars to be understood,
including the frequency pattern in the periodogram, allowing the
approximate rotational frequency to be identified. From a large number
of Be stars observed by TESS, it is shown that the resulting
equatorial rotational velocities, v, are consistent with the projected
rotational velocities, vsini. Furthermore, it is shown that Be stars
are rotating in a broad range of 30%-100% of the critical rotational
velocity. This agrees with several statistical vsini analyses, which
all show that Be stars are very unlikely to be rotating at
near-critical velocities.
Description:
The Be stars in this paper are identified using the BeSS database
(Neiner+ 2011AJ....142..149N 2011AJ....142..149N). This is a catalog of 2330 classical
Be stars, of which 441 were observed by TESS in sectors 1-26
(2018-Jul-25 to 2020-Jul-04) with 2-minute cadence.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 85 441 Classical Be stars observed by TESS
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
J/A+A/368/912 : Polarization & rot. velocities of Be stars (Yudin, 2001)
J/A+A/440/305 : Fundamental param. of fast-rotating B stars (Fremat+, 2005)
J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)
J/AJ/142/112 : KIC photometric calibration (Brown+, 2011)
J/MNRAS/431/2240 : Activity in A-type stars from Kepler (Balona, 2013)
J/ApJS/208/9 : Colors & temperatures of PMS stars (Pecaut+, 2013)
J/MNRAS/447/2714 : Flare stars across the H-R diagram (Balona+, 2015)
J/A+A/595/A132 : Be star rotational velocities distribution (Zorec+, 2016)
J/MNRAS/467/1830 : Starspots on A stars (Balona, 2017)
J/PAZh/43/521 : 3D map of interstellar extinction (Gontcharov, 2017)
J/A+A/620/A145 : Space photometry of the Be stars nu Pup (Baade+, 2018)
J/A+A/610/A70 : 28 Cygni BRITE and SMEI satellite photometry (Baade+, 2018)
J/AJ/156/102 : TESS Input Catalog & Candidate Target List (Stassun+, 2018)
J/MNRAS/485/3457 : Rotational modulation in TESS B stars (Balona+, 2019)
http://basebe.obspm.fr/ : Be Star Spectra (BeSS) database home page
http://heasarc.gsfc.nasa.gov/docs/tess/ : TESS SSC on Heasarc
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- TIC [4827953/470846310] TESS Input catalog number
11- 22 A12 --- Name Star name
24- 36 A13 --- VType Variability class (1)
38- 42 I5 K Teff [5779/39000] Effective temperature
44- 48 F5.2 [Lsun] logL [0.99/9.7] Luminosity relative to Sun (2)
50- 53 I4 km/s vsini [15/480]? Projected rotational velocity (3)
55- 58 I4 km/s ve [23/596]? Equatorial rotational velocity
60- 63 F4.2 --- ve/vc [0.04/1.25]? Ratio of ve to v_critical (4)
65- 69 F5.3 d-1 Frot [0.18/3.3]? Rotation frequency
71- 77 F7.3 10-3 A1 [0.017/55.8]? Amplitude of fundamental frequency,
ppt
79- 85 F7.3 10-3 A2 [0.001/89.2]? Amplitude of first harmonic, ppt
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Note (1): Variability class with abbreviations as follows:
- = No classification possible (13 occurrences)
ACV = α2 CVn star
ACYG = pulsational supergiant
BCEP = beta Cephei;
BE = possible circumstellar variability;
DSCT = delta Scuti;
EA = Algol eclipsing binary;
EB = beta Lyr eclipsing binary;
ELL = Ellipsoidal variable;
FLARE = possible flare;
GDOR = gamma Dor star;
MAIA = Maia variable;
ROT = rotational variable;
SXARI = Chemically peculiar star.
Note (2): The value of log(L/L☉) is determined from the GAIA DR2
parallax and bolometric corrections from Pecaut+ 2013, J/ApJS/208/9 using
a 3D map of interstellar extinction by Gontcharov 2017, J/PAZh/43/521.
Note (3): The vsini is the mean value from the catalogue of
Glebocki+ 2005, III/244 supplemented by values from the literature.
Note (4): The critical rotational velocity was derived using the radius
and the mass estimated from Torres+ 2010, J/other/A+ARV/18.67 adopting
solar abundances and using surface gravities interpolated from the
location in the H-R diagram.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Feb-2023