J/ApJS/275/2 Galactic O-type stars with IACOB, GOSSS and TESS (Shen+, 2024)
A study of stochastic low-frequency variability for Galactic O-type stars.
Shen D.-X., Zhu C.-H., Lu G.-L., Lu X.-Z., He X.-L.
<Astrophys. J. Suppl. Ser., 275, 2 (2024)>
=2024ApJS..275....2S 2024ApJS..275....2S
ADC_Keywords: Stars, O; Spectra, optical; Photometry; Surveys; Spectral types;
Stars, masses; Stars, diameters; Rotational velocities
Keywords: Early-type stars ; Early-type variable stars ; Massive stars
Abstract:
In order to explore how the ubiquitous stochastic low-frequency (SLF)
variability of O-type stars is related to various stellar
characteristics, we compiled a sample of 150 O-type stars observed via
ground-based spectroscopic surveys, alongside photometric data
obtained from the Transiting Exoplanet Survey Satellite (TESS). We
analyzed 298 light curves obtained from TESS Sectors 1-65 for the
stars in our sample. Leveraging the spectroscopic parameters, we used
Bonnsai to determine masses, radii, fractional main-sequence ages,
and mass-loss rates for stars of our sample. Subsequently, we
identified possible correlations between the fitted parameters of SLF
variability and stellar properties. Our analysis unveiled four
significant correlations between the amplitude and stellar parameters,
including mass, radius, fractional main-sequence ages, and mass-loss
rate. For stars with ≳30M☉, we observed a decrease in
characteristic frequency and steepness with increasing radius.
Finally, we compared various physical processes that may account for
the SLF variability with our results. The observed SLF variability may
arise from the combined effects of the iron convection zone (FeCZ) and
internal gravity waves (IGWs), with IGWs potentially more dominant in
the early stages of stellar evolution, and the contribution of FeCZ
becoming more significant as stars evolve. Meanwhile, our results
indicate that the SLF variability of O-type stars bears certain
signatures of the line-driven wind instability and granulation.
Description:
Our original sample consisted of 590 Galactic O-type stars from the
catalogs compiled by Sota+ (2014, III/274; GOSSS) and
Holgado+ (2020, J/A+A/638/A157; IACOB project). After exclusion of
binary stars as described in Section 2 and contamination assessment as
described in Section 3.1, our finalized sample includes 150 Galactic
O-type stars.
Among the stars in our sample, 130 O-type stars are observed by the
high-resolution spectroscopic survey IACOB (Paper I;
Simon-Diaz & Herrero 2014, J/A+A/562/A135). The remaining 20 O-type
stars are only observed by the low-resolution spectroscopic survey
(GOSSS).
Our current data set includes observations from TESS Sectors 1-65
(2018-Jul-25 to 2023-Jun-02).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 144 150 Stellar parameters of stars in our sample
table2.dat 106 298 Results of stochastic low-frequency (SLF)
variability for stars of our sample
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See also:
III/274 : Galactic O-Star Spectroscopic Survey (GOSSS) (Sota+, 2014)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/other/IBVS/5480 : Elements for 80 eclipsing binaries (Otero, 2003)
J/other/IBVS/5495 : Elements for 80 eclipsing binaries. II. (Otero+, 2004)
J/A+A/479/541 : VLT-FLAMES survey of massive stars (Hunter+, 2008)
J/A+A/533/A4 : CoRoT photometry of three O-type stars (Blomme+, 2011)
J/A+A/530/A115 : Rot. massive MS stars evolutionary models (Brott+, 2011)
J/AJ/141/17 : 5-yr spectroscopy & phot. of Deneb (Richardson+, 2011)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/A+A/550/A109 : VLT-FLAMES Tarantula Survey: vsini (Dufton+ 2013)
J/A+A/560/A29 : O-stars in Tarantula Survey (Ramirez-Agudelo+ 2013)
J/ApJS/215/15 : SMaSH+: obs. and companion detection (Sana+, 2014)
J/A+A/562/A135 : Northern Galactic OB stars vsini (Simon-Diaz+, 2014)
J/AJ/152/31 : Spectral classif. of O Vz stars from GOSSS (Arias+, 2016)
J/ApJS/224/4 : GOSSS III. O-type systems (Maiz Apellaniz+, 2016)
J/A+A/597/A22 : Massive O- & B-type stars velocities (Simon-Diaz+, 2017)
J/A+A/619/A97 : CoRoT transit catalogue (Deleuil+, 2018)
J/A+A/613/A65 : Spectroscopic parameters of O-type stars (Holgado+, 2018)
J/AJ/156/83 : Effect of stellar companions on pl. (Ziegler+, 2018)
J/other/NatAs/3.760 : Supergiants low-frequency gravity waves (Bowman+, 2019)
J/A+A/640/A36 : OB stars TESS phot. & high-resolution sp. (Bowman+, 2020)
J/A+A/639/A81 : Variability of OB stars (Burssens+, 2020)
J/A+A/638/A157 : Massive O-type stars near ZAMS detection (Holgado+, 2020)
J/AJ/161/24 : TRICERATOPS predictions for 384 TOIs (Giacalone+, 2021)
J/A+A/665/A150 : Rotational data of Galactic O-type stars (Holgado+ 2022)
J/A+A/674/A212 : Sp. sample of Galactic O9-B9 SGs (de Burgos+, 2023)
J/A+A/678/A24 : Rotation periods of 67163 Kepler stars (Reinhold+, 2023)
J/A+A/676/A28 : Six ULA Cepheids light curves (Tarczay-Nehez+, 2023)
J/A+A/676/A81 : Be stars in the exofield of CoRoT. III. (Zorec+, 2023)
http://heasarc.gsfc.nasa.gov/docs/tess/ : NASA TESS Science Support Center
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 --- f_Name [1/2] Spectral observation flag (1)
3- 16 A14 --- Name Star Name
17 A1 --- m_Name [A] Star name component
19- 23 A5 --- SpT Spectral type
25- 37 A13 --- Lum Luminosity Class
39- 42 F4.2 [Lsun] logLs [3.4/4.27] Log, spectroscopic luminosity
44- 47 F4.2 [Lsun] e_logLs [0.03/0.4] Uncertainty in logLs
49- 53 F5.2 kK Teff [27.7/49.1] Effective temperature
55- 58 F4.2 kK e_Teff [0.5/2.2] Uncertainty in Teff
60- 63 F4.2 [cm.s-2] logg [2.9/4.13] Log, surface gravity
65- 68 F4.2 [cm.s-2] e_logg [0.03/0.3] Uncertainty in logg
70- 74 F5.2 Msun Mass [16/82] Stellar mass
76- 79 F4.2 Msun E_Mass [0/7.4] Upper Uncertainty in Mass
81- 85 F5.2 Msun e_Mass [0.4/15] Lower Uncertainty in Mass
87- 91 F5.2 Rsun Rad [6.17/47.5] Stellar Radius
93- 96 F4.2 Rsun E_Rad [0/1] Upper Uncertainty in Rad
98- 101 F4.2 Rsun e_Rad [0.27/6] Lower Uncertainty in Rad
103- 106 F4.2 --- tau [0.1/0.86] Fractional main sequence age
108- 111 F4.2 --- E_tau [0.01/0.2] Upper Uncertainty in tau
113- 116 F4.2 --- e_tau [0.01/0.3] Lower Uncertainty in tau
118- 122 F5.2 Msun.yr-1 logMdot [-7.9/-5] Mass-loss rate
124- 127 F4.2 Msun.yr-1 E_logMdot [0.07/0.5] Upper Uncertainty in logMdot
129- 132 F4.2 Msun.yr-1 e_logMdot [0.05/0.4] Lower Uncertainty in logMdot
134- 138 F5.1 km.s-1 vmacro [7/440]? Macroturbulent velocity
140- 144 F5.1 km.s-1 vsini [8/140]? Projected rotational velocity
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Note (1): Spectral observation flags as follows:
1 = observed by high-resolution spectroscopic survey IACOB;
2 = observed by low-resolution (GOSSS).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Star Name as in Table 1
16- 19 A4 --- m_Name [AabB ] Star name component
21- 31 A11 --- OName Other name (column added by CDS)
33- 34 I2 --- Sec [5/65] TESS sector
36- 43 F8.2 umag alpha0 [36.7/19698] Scaling factor α0,
amplitude at zero frequency
45- 51 F7.2 umag E_alpha0 [2/5492] Upper Uncertainty in alpha0
53- 59 F7.2 umag e_alpha0 [1.9/3905] Lower Uncertainty in alpha0
61- 65 F5.2 d-1 nu-char [0.1/15.7] Characteristic frequency,
ν{char}
67- 70 F4.2 d-1 E_nu-char [0.02/1.7] Upper Uncertainty in nu-char
72- 75 F4.2 d-1 e_nu-char [0.02/1.7] Lower Uncertainty in nu-char
77- 80 F4.2 --- gamma [0.6/3] Logarithmic amplitude gradient
82- 85 F4.2 --- E_gamma [0.01/0.2] Upper Uncertainty in gamma
87- 90 F4.2 --- e_gamma [0.01/0.2] Lower Uncertainty in gamma
92- 96 F5.2 umag Cw [0.69/33] White noise term
98-101 F4.2 umag E_Cw [0/0.3] Upper Uncertainty in Cw
103-106 F4.2 umag e_Cw [0/0.3] Lower Uncertainty in Cw
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Jul-2025