J/A+A/639/A81 Variability of OB stars (Burssens+, 2020)
Variability of OB stars from TESS southern Sectors 1-13 and high-resolution
IACOB and OWN spectroscopy.
Burssens S., Simon-Diaz S., Bowman D.M., Holgado G., Michielsen M.,
De Burgos A., Castro N., Barba R.H., Aerts C.
<Astron. Astrophys., 639, A81 (2020)>
=2020A&A...639A..81B 2020A&A...639A..81B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, OB ; Asteroseismology ; Spectroscopy
Keywords: techniques: photometric - techniques: spectroscopic - stars: massive -
stars: oscillations
Abstract:
The lack of high-precision long-term continuous photometric data for
large samples of stars has impeded the large-scale exploration of
pulsational variability in the OB star regime. As a result, the
candidates for in-depth asteroseismic modelling have remained limited
to a few dozen dwarfs. The TESS nominal space mission has surveyed the
southern sky, including parts of the galactic plane, yielding
continuous data across at least 27d for hundreds of OB stars.
We aim to couple TESS data in the southern sky with ground-based
spectroscopy to study the variability in two dimensions, mass and
evolution. We focus mainly on the presence of coherent pulsation modes
that may or may not be present in the predicted theoretical
instability domains and unravel all frequency behaviour in the
amplitude spectra of the TESS data.
We compose a sample of 98 OB-type stars observed by TESS in Sectors
1-13 and with available multi-epoch, high-resolution spectroscopy
gathered by the IACOB and OWN surveys. We present the short-cadence 2
min light curves of dozens of OB-type stars, which have one or more
spectra in the IACOB or OWN database. Based on these light curves and
their Lomb-Scargle periodograms, we performed variability
classification and frequency analysis. We placed the stars in the
spectroscopic Hertzsprung-Russell diagram to interpret the variability
in an evolutionary context.
We deduce the diverse origins of the mmag-level variability found in
all of the 98 OB stars in the TESS data. We find among the sample
several new variable stars, including three hybrid pulsators, three
eclipsing binaries, high frequency modes in a Be star, and potential
heat-driven pulsations in two Oe stars.
We identify stars for which future asteroseismic modelling is
possible, provided mode identification is achieved. By comparing the
position of the variables to theoretical instability strips, we
discuss the current shortcomings in non-adiabatic pulsation theory and
the distribution of pulsators in the upper Hertzsprung-Russell
diagram.
Description:
By combining TESS data and multi-epoch high-resolution spectroscopy
gathered by the IACOB and OWN surveys, we provided a variability study
for a sample of OB-type stars in the southern hemisphere based on
visual inspections followed by a frequency analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 95 98 Overview of OB-type stars with available TESS
photometry and IACOB/OWN spectroscopy with
spectral type O4 to B3 considered in this work
tablea1.dat 97 98 Summary of the frequency analysis of the stars
considered in this work
tablea2.dat 79 314 Detailed frequency analysis of multiperiodic
pulsators for 26 stars
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See also:
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sample Sample code (G1)
3- 13 A11 --- Name Star name
15- 35 A21 --- SpType Spectral type
37- 51 A15 --- SpClass Spectral class
53- 56 F4.2 [K] logTeff ? Effective temperature
58- 61 F4.2 [Sun] logLs ? Spectroscopic luminosity
(where Ls=Teff4/g) (2)
63- 65 I3 km/s vsini ? Rotational velocity
67- 69 I3 km/s vmac ? Macroturbulent velocity
71- 73 I3 --- Nsp Number of available spectra
75- 82 A8 --- VarTypesp Spectral variability type (G3)
84- 95 A12 --- VarTypeT TESS variability type (4)
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Note (2): computed using gravities already corrected for centrifugal
acceleration (following the recipe proposed in
Herrero et al., 1992A&A...261..209H 1992A&A...261..209H and Repolust et al., 2004A&A...415..349R 2004A&A...415..349R).
Note (4): TESS Variability types as follows:
EB = eclipsing binary
rot = rotational modulation
SPB = low frequency pulsation modes
beta Cep = high frequency pulsation modes
SLF = stochastic low frequency signal
PQ = poor quality data
cont. = contaminated
A question mark indicates that the TESS light curve is insufficient to
disentangle the contribution of g modes, rotation effects and SLF.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Sample Sample code (G1)
3- 13 A11 --- Name Star Name
17- 25 I9 --- TIC TIC identification number
27 A1 --- n_TIC [+] Note on TIC (2)
29- 33 F5.3 d-1 1/DT Frequency resolution of the amplitude spectra,
defined as the reciprocal of the time-span
35- 37 F3.1 d-1 Window Noise window
39- 46 F8.5 d-1 nudom Dominant frequency
49- 55 F7.5 d-1 e_nudom rms uncertainty on nudom
57- 63 F7.3 mmag Adom Amplitude of dominant frequency
65- 69 F5.3 mmag e_Adom rms uncertainty on Adom
71- 75 F5.2 --- S/N Signal-to-noise ratio
77- 89 A13 --- VarTypesp Spectral variability type (G3)
91- 97 A7 --- Notes Notes (4)
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Note (2): + indicates that the light curve was extracted using our own method.
Note (4): Notes as follows:
IV = if the light curve is of poor quality or contaminated (invalid)
HARM = if periodogram is dominated by harmonics
* = if more than one frequency was measured
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Sample [A-F] Sample code (1)
3- 13 A11 --- Name Star name
14- 17 A4 --- FreqName Frequency designation
21- 27 F7.4 d-1 Freq Frequency value
29- 34 F6.4 d-1 e_Freq rms uncertainty on Freq
37- 43 F7.3 mmag Amp Amplitude of variation of Freq
45- 49 F5.3 mmag e_Amp rms uncertainty on Amp
51- 56 F6.3 --- phi [-0.5/0.5] Phase
58- 62 F5.3 --- e_phi rms uncertainty on phi
65- 68 F4.1 --- S/N Signal-to-noise ratio
71- 79 A9 --- Notes Notes (2)
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Note (1): Sample as follows:
A = beta Cep stars
B = SPB stars
C = Hybrid stars
D = Be/Oe stars
E = Magnetic stars
F = Eclipsing binaries
Note (2): nuorb indicates the orbital frequency, which is not always directly
measured but derived from harmonics. In the case of HD 47129, nuorb refers to
the orbital frequency measured by Mahy et al. (2011A&A...525A.101M 2011A&A...525A.101M).
Potential combinations, harmonics or multiplet memberships are indicates as
tp/tp? (triplet) or mp/mp? (multiplet) followed by a number if more than one
was detected. See Appendix B for more details.
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Global notes:
Note (G1): Sample code as follows
1 = O-type dwarfs and subgiants (V and IV)
2 = O-type giants, bright giants and supergiants (III, II and I)
3 = Early B-type dwarfs, subgiants and giants (V, IV, and III)
4 = B-type giants, bright giants and supergiants (III, II, and I)
5 = Magnetic O- and B-type stars
6 = Oe and Be stars
Note (G3): Spectroscopic Variability types as follows:
SB1 = single lined spectroscopic binary
SB2 = double lined spectroscopic binary
LPV = line profile variability in photospheric lines
WVa = Variability of the Hα line in absorption
WVe = Variability of the Hα line in emission
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 17-Sep-2020