J/A+A/613/A70 Be stars in the exofield of CoRoT. II. (Semaan+, 2018)
Study of a sample of faint Be stars in the exofield of CoRoT. II.
Pulsation and outburst events: Time series analysis of photometric variations.
Semaan T., Hubert A.M., Zorec J., Gutierrez-Soto J., Fremat Y.,
Martayan C., Fabregat J., Eggenberger P.
<Astron. Astrophys. 613, A70 (2018)>
=2018A&A...613A..70S 2018A&A...613A..70S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Stars, Be
Keywords: stars: early-type - stars: emission-line, Be - stars: rotation -
stars: oscillations
Abstract:
The class of Be stars are the epitome of rapid rotators in the main
sequence. These stars are privileged candidates for studying the
incidence of rotation on the stellar internal structure and on
non-radial pulsations. Pulsations are considered possible mechanisms
to trigger mass-ejection phenomena required to build up the
circumstellar disks of Be stars.
Time series analyses of the light curves of 15 faint Be stars observed
with the CoRoT satellite were performed to obtain the distribution of
non-radial pulsation (NRP) frequencies in their power spectra at
epochs with and without light outbursts and to discriminate pulsations
from rotation-related photometric variations.
Standard Fourier techniques were employed to analyze the CoRoT light
curves. Fundamental parameters corrected for rapid-rotation effects
were used to study the power spectrum as a function of the stellar
location in the instability domains of the Hertzsprung-Russell (H-R)
diagram.
Frequencies are concentrated in separate groups as predicted for
g-modes in rapid B-type rotators, except for the two stars that are
outside the H-R instability domain. In five objects the variations in
the power spectrum are correlated with the time-dependent outbursts
characteristics. Time-frequency analysis showed that during the
outbursts the amplitudes of stable main frequencies within 0.03d-1
intervals strongly change, while transients and/or frequencies of low
amplitude appear separated or not separated from the stellar
frequencies. The frequency patterns and activities depend on evolution
phases: i) the average separations between groups of frequencies are
larger in the zero-age main sequence (ZAMS) than in the terminal age
main sequence (TAMS) and are the largest in the middle of the MS
phase; ii) a poor frequency spectrum with f<1d-1 of low amplitude
characterizes the stars beyond the TAMS; and iii) outbursts are seen
in stars hotter than B4 spectral type and in the second half of the
MS.
The two main frequency groups are separated by
δf=(1.24±0.28).f{rot} in agreement with models of prograde
sectoral g-modes (m=-1,-2) of intermediate-mass rapid rotators.
The changes of amplitudes of individual frequencies and the presence
of transients correlated with the outburst events deserve further
studies of physical conditions in the subatmospheric layers to
establish the relationship between pulsations and sporadic
mass-ejection events.
Description:
Tables 7 to 22 contain the frequencies that were derived with the
FREQFIND code from the CoRoT light curves of 15 Be stars; some of them
were observed in two different runs, while star No 9 was observed in
three runs. For each Be star is given the CoRoT number, the number of
the star attributed in Paper I (Semaan et al., 2013A&A...551A.130S 2013A&A...551A.130S),
the frequency number ordered by increasing value of frequencies, the
value of the frequency in d-1 (cycle/day), the value of the frequency
in micro-Hertz, the amplitude of the frequency in ppm, the phase, the
signal to noise ratio (S/N), the order number N_FREQ of the frequency
as find by the FREQFIND code, the mark S indicates the 20 frequencies
with larger amplitude among which the combinations and harmonics were
searched. The combinations and harmonics found are indicated. Each
group of frequencies is separated by a horizontal line.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 89 19 Some basic characteristics of the CoRoT data
table7.dat 70 74 CoRoT 101486436 data from LRC1 run light curve
table8.dat 58 10 CoRoT 102595654 data from LRA1 run light curve
table9.dat 81 95 CoRoT 102656190 data from LRA1 run light curve
table10.dat 67 48 CoRoT 102672979 data from LRA1 run light curve
table11.dat 74 84 CoRoT 102686433 data from LRA1 run light curve
table12.dat 136 64 CoRoT 102719279 data from LRA1 run (64 frequencies)
and IR1 (24 frequencies) run light curves
table13.dat 89 70 CoRoT 102719279 data from LRA1 run (64 frequencies),
LRA6 run (42 frequencies) and
IR1 run (24 frequencies) light curves
table14.dat 93 8 CoRoT 102725623 data from LRA1 run (8 frequencies)
and IR1 run (2 frequencies) light curves
table15.dat 70 62 CoRoT 102728404 data from LRA1 run light curve
table16.dat 140 68 CoRoT 102766835 data from LRA1 run (69 frequencies)
and IR1 run (23 frequencies) light curves
table17.dat 68 30 CoRoT 102785204 data from LRA1 run light curve
table18.dat 80 114 CoRoT 102785480 data from IR1 run light curve
table19.dat 74 44 CoRoT 102825808 data from IR1 run light curve
table20.dat 70 26 CoRoT 102829773 data from IR1 run light curve
table21.dat 68 7 CoRoT 102847615 data from IR1 run light curve
table22.dat 67 32 CoRoT 102904910 data from IR1 run light curve
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See also:
B/corot : CoRoT observation log (N2-4.4) (CoRoT 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [CoRoT]
7- 15 I9 --- CoRoT CoRoT number
17- 18 I2 --- Seq [1/22] Sequential number, as in Paper I
(Semaan et al., 2013A&A...551A.130S 2013A&A...551A.130S)
20- 24 F5.2 mag Vmag V magnitude
26- 29 A4 --- Run Run
31- 40 F10.5 d t0 CoRoT time of phase 0 (HJD with origin on
01/01/2000 at 12h00 UT)
42- 47 I6 --- Pts Number of data points
49- 53 A5 --- Sample Sampling: S1=512s, S2=32s
55- 61 F7.3 d DT Total duration of CoRoT observations
63- 68 F6.4 d-1 Df Frequency accuracy
70- 72 I3 --- Nf number of identified frequencies
74- 77 I4 ppm Amin lower amplitude detected
79- 89 A11 --- FileName Name of the table with frequencies,
amplitudes and phases
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Byte-by-byte Description of file: table[789].dat table1[015789].dat table2?.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- nr Identification frequencies
6- 7 A2 --- n_nr [p fab] p or f for frequencies with
uniform period separation
8- 15 F8.5 d-1 Freq Frequency in cycle/day
17- 25 F9.5 uHz FreqHz Frequency in micron-Hertz
27- 31 I5 ppm Amm Amplitude of frequency in ppm
33- 35 F3.1 rad Phase Phase from 0 to 2pi
37- 41 F5.1 --- S/N Signal to noise ratio
43- 45 I3 --- Nfreqfind Frequency order of determination with the
FREQFIND code
47 A1 --- Power [S] Indication that the frequency is among
the 20th with higher amplitude
49- 84 A36 --- Com Combinations and harmonics
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Byte-by-byte Description of file: table12.dat table16.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- nr1 Identification frequencies
6- 7 A2 --- n_nr1 [f ab] p or f for frequencies with
uniform period separation
9- 15 F7.5 d-1 Freq1 ? Frequency in cycle/day
17- 24 F8.5 uHz FreqHz1 ? Frequency in micron-Hertz
26- 30 I5 ppm Amm1 ? Amplitude of frequency in ppm
32- 34 F3.1 rad Phase1 ? Phase from 0 to 2pi
36- 39 F4.1 --- S/N1 ? Signal to noise ratio
41- 42 I2 --- Nfreqfind1 ? Frequency order of determination
with the FREQFIND code
44 A1 --- Power1 [S] Indication that the frequency is
among the 20th with higher amplitude
46- 76 A31 --- Com1 Combinations and harmonics
78- 81 A4 --- nr2 Identification frequencies
83- 89 F7.5 d-1 Freq2 ? Frequency in cycle/day
91- 98 F8.5 uHz FreqHz2 ? Frequency in micron-Hertz
100-104 I5 ppm Amm2 ? Amplitude of frequency in ppm
106-108 F3.1 rad Phase2 ? Phase from 0 to 2pi
110-113 F4.1 --- S/N2 ? Signal to noise ratio
115-116 I2 --- Nfreqfind2 ? Frequency order of determination
with the FREQFIND code
118 A1 --- Power2 [S] Indication that the frequency is
among the 20th with higher amplitude
120-140 A21 --- Com2 Combinations and harmonics
-------------------------------------------------------------------------------
Byte-by-byte Description of file: table13.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- nr1 Identification frequencies
6- 12 F7.5 d-1 Freq1 ? Frequency in cycle/day
14- 17 A4 --- nr2 Identification frequencies
19- 25 F7.5 d-1 Freq2 ? Frequency in cycle/day
27- 34 F8.5 uHz FreqHz2 ? Frequency in micron-Hertz
36- 39 I4 ppm Amm2 ? Amplitude of frequency in ppm
41- 43 F3.1 rad Phase2 ? Phase from 0 to 2pi
45- 48 F4.1 --- S/N2 ? Signal to noise ratio
50- 51 I2 --- Nfreqfind2 ? Frequency order of determination
53- 56 A4 --- nr3 Identification frequencies
58- 64 F7.5 d-1 Freq3 ? Frequency in cycle/day
66- 95 A30 --- Com Combinations and harmonics
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Byte-by-byte Description of file: table14.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- nr1 Identification frequencies
5- 11 F7.5 d-1 Freq1 Frequency in cycle/day
13- 20 F8.5 uHz FreqHz1 Frequency in micron-Hertz
22- 24 I3 ppm Amm1 Amplitude of frequency in ppm
26- 28 F3.1 rad Phase1 Phase from 0 to 2pi
30- 32 F3.1 --- S/N1 Signal to noise ratio
34 I1 --- Nfreqfind1 Frequency order of determination
with the FREQFIND code
36 A1 --- Power1 [S] Indication that the frequency is
among the 20th with higher amplitude
38- 45 A8 --- Com1 Combinations and harmonics
47- 49 A3 --- nr2 Identification frequencies
51- 57 F7.5 d-1 Freq2 ? Frequency in cycle/day
59- 66 F8.5 uHz FreqHz2 ? Frequency in micron-Hertz
68- 70 I3 ppm Amm2 ? Amplitude of frequency in ppm
72- 74 F3.1 rad Phase2 ? Phase from 0 to 2pi
76- 78 F3.1 --- S/N2 ? Signal to noise ratio
80 I1 --- Nfreqfind2 ? Frequency order of determination
with the FREQFIND code
82 A1 --- Power2 [S] Indication that the frequency is
among the 20th with higher amplitude
84- 93 A10 --- Com2 Combinations and harmonics
-------------------------------------------------------------------------------
Acknowledgements:
Thierry Semann, thierry.semaan(at)unige.ch
References:
Semaan et al., Paper I 2013A&A...551A.130S 2013A&A...551A.130S
(End) Thierry Semann [Geneve univ.], Patricia Vannier [CDS] 01-Feb-2018