J/MNRAS/505/1476 Asteroseismic study of TESS mission's DSCTs (Hasanzadeh+, 2021)
Relations between the asteroseismic indices and stellar parameters of δ
Scuti stars for two years of TESS mission.
Hasanzadeh A., Safari H., Ghasemi H.
<Mon. Not. R. Astron. Soc. 505, 1476-1484 (2021)>
=2021MNRAS.505.1476H 2021MNRAS.505.1476H (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Photometry ; Optical ; Spectroscopy ;
Stars, standard
Keywords: asteroseismology; techniques: photometric -
stars: variables: δ Scuti
Abstract:
We investigate the relationship between the asteroseismic indices and
the physical quantities of 438 δ Scuti (DSCT) stars observed by
the Transiting Exoplanet Survey Satellite (TESS) mission at 26
sectors. We study the scaling relations of stellar parameters
(effective temperature, surface gravity, density, etc.) and
asteroseismic indices such as fundamental frequency, large frequency
separation (Δν), frequency of the highest peak in the spectrum,
and the peak of the envelope of oscillation mode (νmax) for DSCT
targets. Using an empirical relation and a 2D autocorrelation method,
we determine the large frequency separation for targets. We obtain a
highly positive correlation between the fundamental radial pressure
mode and the large separation for one- third of targets. We find a
scaling relation between the large separation and νmax as
Δν= 0.49νmax{0.68}, which is similar to that of the
solar-like and red giant stars. We show a strong positive correlation
between the effective temperature and νmax (Pearson correlation
R = 0.65). We also obtain a very strong positive correlation (R = 0.86)
between the effective temperature multiplying by the surface gravity
and νmax.
Description:
We selected about 4000 targets from TESS Asteroseismic Science
Consortium (TASC)-WG4 (AF-stars)2 list (e.g https://tasoc.dk/wg4). We
checked our DSCT star candidates with Kepler's catalogue
(Uytterhoeven et al. 2011A&A...534A.125U 2011A&A...534A.125U, Cat. J/A+A/534/A125 ;
Bradley et al. 2015AJ....149...68B 2015AJ....149...68B, Cat. J/AJ/149/68; Bowman & Kurtz
2018MNRAS.476.3169B 2018MNRAS.476.3169B). Also, we checked out the regular frequency
spacing (echelle diagram) in their pulsation spectra (see section 3.2) as
an additional criterion for selecting the targets. Our goal is to
analyse the DSCT stars with many frequencies, so we limited our list
by removing stars with a single (or double) frequency from the
analysis. So, considering the above criteria, the final list is
reduced to 438 Scuti stars.
We used the latest TESS catalogue (Stassun et al. 2019AJ....158..138S 2019AJ....158..138S,
Cat. IV/38) to extract the positions, magnitudes, and stellar
parameters (such as effective temperature, mass, surface gravity,
stellar density, and luminosity) for DSCT stars.
First, we did light-curve analysis, we analysed the frequency modes of
438 selected DSCT stars. Secondly, we focused on asteroseismic
analysis. In asteroseismology, a star's basic information can be
deduced from the seismic indices. The relations between the global
seismic indices (frequency of the highest peak amplitude, fundamental
frequency, large frequency separation, etc.) and stellar
characteristics (mass, gravity, temperature, radius, etc.) have been
widely developed (Coelho et al. 2015MNRAS.451.3011C 2015MNRAS.451.3011C; Yu et al.
2018ApJS..236...42Y 2018ApJS..236...42Y, Cat. J/ApJS/236/42 ; Barcelo Forteza et al.
2020A&A...638A..59B 2020A&A...638A..59B, Cat. J/A+A/638/A59)
TESS catalogue determines the stellar parameters by applying the Gaia
DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345), photometric,
and spectroscopic data (such as 2MASS Cutri et al. 2003yCat.2246....0C 2003yCat.2246....0C
Cat. II/246, LAMOST Luo et al. 2019yCat.5164....0L 2019yCat.5164....0L Cat. V/164), as
well as a set of empirical relations. Stassun et al.
(2019AJ....158..138S 2019AJ....158..138S, Cat. IV/38) described the details of methods. We
compared temperatures and radii extracted from TESS with Gaia DR2
catalogues. Here, we studied statistical analysis and scaling
relations for asteroseismic and stellar parameters of DSCT stars. The
table1.dat represents the asteroseismic indices and stellar parameters
for the sample of 438 DSCT stars.
Additionally, We applied the maximum-likelihood method to estimate the
fitting parameters (frequencies in the table1.dat) via a numerical
optimization technique. Also, we used the Markov Chain Monte Carlo
(MCMC) approach to investigate the uncertainties in the observations
propagated into the fit parameters (Goodman & Weare 2010, Commun.
Appl. Math. Comput. Sci., 5, 65). Foreman-Mackey et al.
2013PASP..125..306F 2013PASP..125..306F) gave a brief discussion of MCMC and details of
codes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 136 438 Observational, physical and asteroseismic
properties of the 438 DSCT stars
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See also:
J/A+A/534/A125 : Variability of A- and F-stars from Kepler (Uytterhoeven+ 2011)
J/AJ/149/68 : A-F type variable stars from Kepler (Bradley+, 2015)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/ApJS/236/42 : Asteroseismology of ∼16000 Kepler red giants (Yu+, 2018)
J/A+A/638/A59 : delta Scuti stars with TESS (Barcelo Forteza+, 2020)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
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 Tess Input Catalog identifier (TIC) (1)
11- 25 A15 --- Sector Sky mapped sectors surveyed by TESS mission
which divides the sky into 26 sectors
(Sector) (1)
27- 34 F8.4 deg RAdeg Right Ascension (J2000) (1)
36- 43 F8.4 deg DEdeg Declination (J2000) (1)
45- 48 I4 K Teff Effective temperature (Teff) (1)
50- 52 I3 K e_Teff ? Mean error on Teff (Teff_error) (1)
54- 57 F4.2 Msun M Stellar mass (M) (1)
59- 62 F4.2 Msun e_M ? Mean error on M (M_error) (1)
64- 67 F4.2 Rsun R Stellar radius (R) (1)
69- 72 F4.2 Rsun e_R ? Mean error on R (R_error) (1)
74- 77 F4.2 [cm/s2] logg Surface gravity in log scale (logg) (1)
79- 82 F4.2 [cm/s2] e_logg ? Mean error on log(g) (logg_error) (1)
84- 89 F6.2 Lsun L Stellar luminosity (L) (1)
91- 95 F5.2 Lsun e_L ? Mean error on L (L_error) (1)
97-101 F5.3 Sun rho Stellar density in solar scale (rho) (1)
103-107 F5.3 Sun e_rho Mean error on rho (rho_error) (1)
109-113 F5.2 mag Tmag TESS magnitude (TESSmag) (1)
115-119 F5.2 d-1 nuf ? Fundamental frequency (nuf) (2)
121-125 F5.2 d-1 nu(Amax) The frequency related to the highest peak
amplitude of the DSCT star spectrum
(nuAmax) (3)
127-131 F5.2 d-1 numax The peak of the envelope of oscillation
mode (numax) (4)
133-136 F4.2 d-1 Dnu The large frequency separation (Deltanu) (5)
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Note (1): From the TESS Input Catalog, Stassun K.G. et al. 2018AJ....156..102S 2018AJ....156..102S,
Cat. IV/38.
Note (2): We applied the following criteria to identify the fundamental mode
of oscillations for our targets. The lowest frequency with a strong
amplitude (with amplitude usually greater than 0.2 highest peak to
ensure that the mode is above the noise level and an SNR of more
than four) and satisfied the period-luminosity relation.
Note (3): Due to amplitude modulation mechanisms and noise background
(Bowman D. M. 2017, Amplitude Modulation of Pulsation Modes in
Delta Scuti Stars.), the ν(Amax) may change with time.
Therefore, it was suggested to use the frequency of the envelope's
peak (νmax) instead of ν(Amax) in an SNR periodogram.
Note (4): Applying an autocorrelation method
(Mosser & Appourchaux 2009A&A...508..877M 2009A&A...508..877M), we determined νmax.
The autocorrelation method applied on several windows of the frequency
spectrum to obtain the frequency range for the modes' envelope.
To do this, first, we reduced the background from the smoothed
spectrum. Secondly, we applied the autocorrelation for a window
of the background smoothed spectrum. Thirdly, a Gaussian curve
is fitted to the mean collapsed correlation within each window.
Finally, we determined the frequency (νmax) of the peak in
the Gaussian fitted curve. Viani et al. 2019ApJ...879...33V 2019ApJ...879...33V gave
the details of the method to determine the νmax.
Note (5): Large frequency separation (Δ(nu) is another important seismic
quantity in asteroseismology. For a given angular degree (l),
Δν defines the average frequency spacing between consecutive
radial modes (Aerts et al. 2010, Asteroseismology. Springer, Berlin).
See section 3.2 for details on determination method.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 24-May-2024