J/MNRAS/510/5743 Variable stars study with TESS (Balona, 2022)
Rapidly oscillating TESS A-F main-sequence stars are the roAp stars
a distinct class?
Balona L.A.
<Mon. Not. R. Astron. Soc. 510, 5743-5759 (2022)>
=2022MNRAS.510.5743B 2022MNRAS.510.5743B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, peculiar ; Stars, variable ; Stars, A-type ;
Stars, B-type ; Stars, F-type ; Stars, late-type ;
Stars, double and multiple ; Effective temperatures ;
Asteroseismology ; Photometry ; Optical ; Spectral types
Keywords: stars: chemically peculiar - stars: oscillations
Abstract:
From sector 1-44 TESS observations, 19 new rapidly oscillating Ap
(roAp) stars, 103 ostensibly non-peculiar stars with roAp-like
frequencies, and 617 δ Scuti stars with independent frequencies
typical of roAp stars were found. Examination of all chemically
peculiar stars observed by TESS resulted in the discovery of 199 Ap
stars that pulsate as δ Sct or γ Dor variables. The
fraction of pulsating Ap stars is the same as the fraction of
pulsating chemically normal stars. There is no distinct separation in
frequency or radial order between chemically peculiar δ Sct
stars and roAp stars. In fact, all the features that originally
distinguished roAp from δ Sct stars in the past have
disappeared. There is no reason to assume that the high frequencies in
roAp stars are driven by a different mechanism from the high
frequencies in chemically normal stars. However, chemically peculiar
stars are far more likely to pulsate with high frequencies. The term
'roAp' should be dropped: all roAp stars are normal δ Scuti
stars.
Description:
The idea that Ap stars do not pulsate is not correct. These new
discoveries show that all the characteristics separating roAp stars
from δ Sct stars are no longer applicable. It is clear that
whatever mechanism drives high frequencies in normal stars must surely
drive the high frequencies in 'roAp' stars as well. The equally spaced
frequencies seen in some roAp stars are not seen in normal δ Sct
stars. This is due to the action of a strong magnetic field on the
atmospheric structure and does not require a separate pulsation
mechanism. The aim of this paper is to present new discoveries of
'roAp' stars and non-peculiar roAp-like pulsators as well as a survey
of pulsation in chemically peculiar stars. Using these results, it is
argued that a suitable definition of the roAp class does not exist.
From sector 1-37 TESS observations, variability classification of
76431 stars was made using light curves and periodograms and
approximate effective temperatures from photometry or spectral types,
(as explicited in the section 2 The data and stellar parameters). As
for TESS data, we created based on extraction method 't' a deduced
effective temperature catalogue of 574 object entries with lowest and
best 't' values. In our study, this table1.dat is used to determine
the adopted Teff for the 443 stars listed in the tablea1-a3.dat
tables reporting mostly TESS roAp, δ Scuti or γ variables.
Next, as described in the section 6 Hybrid δ Sct and H-F δ
Sct stars, for each object, a list of significant frequency peaks was
compiled. Of these stars, 8529 are identified as delta Scuti
variables. Many of these stars have frequency peaks higher than 60
1/d, but in many cases the high frequencies, nu, can be explained as a
linear combination of two parent frequencies, nu1, nu2, such that
nu = n1*nu1 + n2*nu2 where n1 and n2 are positive, zero or
negative integers less than or equal to 7. Thus, table3.dat reports
617 stars which are those delta Scuti stars having frequencies higher
than 60 1/d with a signal-to-noise ratio S/N > 4, but which cannot be
explained as combination frequencies. In deciding whether a
combination, nu, is significantly different from the observed
frequency, nu_obs, the criterion |nu - nu_obs| < 3*σ was used,
where sigma is given by
σ2 = sigmaobs2 + sigma12 + sigma22 where the
sigmas on the right hand side refer to the standard deviations of the
observed frequency and the two parent frequencies.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 37 574 Catalogue of effective temperatures Teff
table3.dat 81 617 List of 617 new δ Sct stars with independent
high frequencies exceeding 60 d-1
tablea1.dat 105 131 *List of known roAp or roA stars even those not
observed by TESS
tablea2.dat 93 199 *Chemically peculiar stars known to be
δ Scuti or γ variables
tablea3.dat 104 122 List of new roAp and roA stars unreported TESS
stars with Teff > 6000 K and with at least one
frequency peak higher than 60 d-1
--------------------------------------------------------------------------------
Note on tablea1.dat and tablea2.dat: A colon ":" on the variable type signifies
stars with a signal-to-noise ratio S/N<5. More, the variability types in square
brackets [] means that the high frequecies are not detected in the TESS light
curve.
--------------------------------------------------------------------------------
See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
B/pastel : The PASTEL catalogue (Soubiran+, 2016-)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
B/mk : Catalogue of Stellar Spectral Classifications (Skiff, 2009-)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC TESS Input Catalog identifier (ID_TIC)
11 I1 --- n_Teff Method used to derived Teff (t) (1)
13- 17 I5 K Teff Effective temperature (Teff)
19- 37 A19 --- r_Teff Reference Bibcode for Teff (Ref)
--------------------------------------------------------------------------------
Note (1): Method used to derived Teff are as follows:
1 = Spectroscopic measurements, derived from fitting a model
atmosphere to the stellar spectrum, 263 stars of our sample
2 = Estimated from Stromgren, Geneva, or other narrow-band
photometry, 132 stars of our sample
3 = Derived from the spectral energy distribution or similar
method, 7 stars of our sample
4 = From the Kepler or TESS catalogues, 122 stars of our sample
5 = Estimated from the spectral type, 50 stars of our sample
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC TESS Input Catalog identifier (ID_TIC)
11- 25 A15 --- Name Star name (Name)
27- 40 A14 --- VarType Variability class (Var_type) (1)
42- 48 F7.3 1/d Freq Pulsation frequency (Freq)
50- 54 I5 K Teff Effective temperature (Teff)
56- 59 F4.2 [Lsun] LogL* Luminosity L* in solar units (LogL/Lsun)
61- 66 F6.3 d Prot ? Rotation period
68- 81 A14 --- SpType Spectral type (2)
--------------------------------------------------------------------------------
Note (1): Variability classes are based General Catalogue of Variable Stars
(GCVS; Samus et al. 2017ARep...61...80S 2017ARep...61...80S, Cat. B/gcvs are as follows:
DSCT = Pulsating Variable Stars, Delta Scuti types
ACV = Rotating Variable Stars, Alpha2 Canum Venaticorum variables
ROAP = The rapidly oscillating Ap roAp stars pulsate in a limited
high-frequency range, typically above 60 d-1.
EA = Close Binary Eclipsing Systems, class based on the shape of
the light curve, Algol (Beta Persei)-type eclipsing systems
ROA = Rapidly oscillating stars roA, these star have not a confirmed
spectral type but must be assigned to a star which would be
classified as roAp on the basis of the frequencies
ELL = Rotating ellipsoidal variables (b Per, Alpha Vir), these are
close binary systems with ellipsoidal components
FLARE = There is a further discovery that might impact on the driving
of the oscillations. Kepler and TESS light curves indicate
that the light from A and B stars is modulated by rotation.
Flares are sometimes seen in A and late B stars
EP = Stars showing eclipses by their planets
Note (2): These are subtypes of A, B and F types.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC TESS Input Catalog identifier (ID_TIC)
11 A1 --- n_Name Indicates the star was not observed by TESS
13- 35 A23 --- Name Star name (Name)
37- 59 A23 --- VarType Variability class (Var_type) (1)
61- 67 F7.3 1/d Freq Pulsation frequency (Freq)
69- 73 I5 K Teff Effective temperature (Teff)
75- 78 A4 [Lsun] LogL* Luminosity L* in solar units (LogL/Lsun)
80- 87 A8 d Prot ? Rotation period
89-105 A17 --- SpType Spectral type (2)
--------------------------------------------------------------------------------
Note (1): As for table3.dat, variability classes are based similarly and also
is expanded to include other classes as follows:
DSCT = Pulsating Variable Stars, Delta Scuti types
ACV = Rotating Variable Stars, Alpha2 Canum Venaticorum variables
ROAP = The rapidly oscillating Ap roAp stars pulsate in a limited
high-frequency range, typically above 60 d-1.
ROA = Rapidly oscillating stars roA, these star have not a confirmed
spectral type but must be assigned to a star which would be
classified as roAp on the basis of the frequencies
GDOR = Pulsating Variable Stars, Gamma Doradus stars. Early type F
dwarfs showing multiple periods
ROT = The variability is suspected to be due to rotation, the
criterion for ROT requires the presence of just a single,
isolated frequency peak below 4 d-1 or a peak and its
harmonic. It is not always possible to distinguish rotation
from binary effects, but to minimize such contamination, the
ROT class is restricted to amplitudes below 10 millimags
SXARI = Rotating Variable Stars, SX Arietis-type variables these are
main-sequence B0p-B9p stars with variable-intensity He I and
Si III lines and magnetic fields
r = Rotational sidelobes present in light curve
s = Variable amplitudes and/or frequencies
h = 2, 3 or 4h means highest harmonic frequencies present
Note (2): These are subtypes of A or F types.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC TESS Input Catalog identifier (ID_TIC)
11 A1 --- n_Name Indicates the star was not observed by TESS
13- 35 A23 --- Name Star name (Name)
37- 57 A21 --- VarType Variability class (Var_type) (1)
59- 63 I5 K Teff Effective temperature (Teff)
65- 68 F4.2 [Lsun] LogL* ? Luminosity L* in solar units (LogL/Lsun)
70- 75 F6.3 d Prot ? Rotation period
77- 93 A17 --- SpType Spectral type (2)
--------------------------------------------------------------------------------
Note (1): As for table3.dat, variability classes are based similarly and also
is expanded to include other classes as follows:
DSCT = Pulsating Variable Stars, Delta Scuti types
DSCTHF = DSCT with slightly lower frequencies (stars with frequency
peaks extending to at least 50 d-1 but lower than 60 d-1
BCEP = Pulsating Variable Stars, variables of the Beta Cephei type
ACV = Rotating Variable Stars, Alpha2 Canum Venaticorum variables
ROAP = The rapidly oscillating Ap roAp stars pulsate in a limited
high-frequency range, typically above 60 d-1
ROA = Rapidly oscillating stars roA, these star have not a
confirmed spectral type but must be assigned to a star which
would be classified as roAp on the basis of the frequencies
GDOR = Pulsating Variable Stars, Gamma Doradus stars. Early type F
dwarfs showing multiple periods
ROT = The variability is suspected to be due to rotation, the
criterion for ROT requires the presence of just a single,
isolated frequency peak below 4 d-1 or a peak and its
harmonic. It is not always possible to distinguish rotation
from binary effects, but to minimize such contamination, the
ROT class is restricted to amplitudes below 10 millimags
E = Eclipsing binary systems
EA = Close Binary Eclipsing Systems, class based on the shape of
the light curve, Algol (Beta Persei)-type eclipsing systems
EB = Close Binary Eclipsing Systems, class based on the shape of
the light curve, Beta Lyrae-type eclipsing systems
ELL = Rotating ellipsoidal variables (b Per, Alpha Vir), these are
close binary systems with ellipsoidal components
MAIA = A chemically peculiar star and the prototype of the Maia
variable class of variable star
SPB = Slowly pulsating B-type star
SXARI = Rotating Variable Stars, SX Arietis-type variables these are
main-sequence B0p-B9p stars with variable-intensity He I and
Si III lines and magnetic fields
r = Rotational sidelobes present in light curve
s = Variable amplitudes and/or frequencies
2h = means highest harmonic frequencies present
Note (2): These are subtypes of A, B or F types.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC TESS Input Catalog identifier (ID_TIC)
11- 35 A25 --- Name Star name (Name)
37- 60 A24 --- VarType Variability class (Var_type) (1)
62 A1 --- n_VarType Variable types note signifies stars with
ratio S/N < 5
64- 70 F7.3 1/d Freq Pulsation frequency (Freq)
72- 76 I5 K Teff Effective temperature (Teff)
78- 82 F5.2 [Lsun] LogL* Luminosity L* in solar units (LogL/Lsun)
84- 90 F7.3 d Prot ? Rotation period
92-104 A13 --- SpType Spectral type (2)
--------------------------------------------------------------------------------
Note (1): As for table3.dat, variability classes are based similarly and also
is expanded to include other classes as follows:
DSCT = Pulsating Variable Stars, Delta Scuti types
BCEP = Pulsating Variable Stars, variables of the Beta Cephei type
ACV = Rotating Variable Stars, Alpha2 Canum Venaticorum variables
ROAP = The rapidly oscillating Ap roAp stars pulsate in a limited
high-frequency range, typically above 60 d-1
ROA = Rapidly oscillating stars roA, these star have not a
confirmed spectral type but must be assigned to a star which
would be classified as roAp on the basis of the frequencies
GDOR = Pulsating Variable Stars, Gamma Doradus stars. Early type F
dwarfs showing multiple periods
ROT = The variability is suspected to be due to rotation, the
criterion for ROT requires the presence of just a single,
isolated frequency peak below 4 d-1 or a peak and its
harmonic. It is not always possible to distinguish rotation
from binary effects, but to minimize such contamination, the
ROT class is restricted to amplitudes below 10 millimags
FLARE = There is a further discovery that might impact on the driving
of the oscillations. Kepler and TESS light curves indicate
that the light from A and B stars is modulated by rotation
EA = Close Binary Eclipsing Systems, class based on the shape of
the light curve, Algol (Beta Persei)-type eclipsing systems
EP = Stars showing eclipses by their planets
SPB = Slowly pulsating B-type star
r = Rotational sidelobes present in light curve
2h = means highest harmonic frequencies present
Note (2): These are subtypes of A, B or F types.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 09-Dec-2024