J/AJ/170/199 Pulsation timing of two sdB binaries from TESS (Otani+, 2025)
A search for subdwarf B binaries using pulsation timing from TESS.
Otani T., Baran A.S., Spence L.C., von Hippel T., Lozano E.L.-,
Clark J.M.
<Astron. J., 170, 199 (2025)>
=2025AJ....170..199O 2025AJ....170..199O
ADC_Keywords: Stars, double and multiple; Photometry; Optical; Exoplanets;
Stars, B-type; Stars, subdwarf; Stars, variable
Keywords: B subdwarf stars ; Pulsating variable stars ; Binary stars ;
Timing variation methods ; Pulsation frequency method
Abstract:
Hot subdwarf B (sdB) stars are post-main-sequence stars of high
temperature and gravity. Approximately 30% of sdBs exhibit stable
pressure and/or gravity-mode pulsations, which can be used via the
timing method to test for companion stars and determine their orbital
solutions. We used short cadence data from the Transiting Exoplanet
Survey Satellite (TESS) to search for previously undiscovered
companions to sdBs. In this paper, we focus on searching for
companions with orbital periods shorter than 13.5days which are
detectable within one sector of TESS data (about 27days). The timing
method requires that we derive pulsation frequencies in subsets of
data significantly shorter than the periods we are searching for,
which we set at 0.5-1.5day. We investigated ten sdB stars with
previously detected p-mode pulsations for which at least one p-mode
pulsation remains detectable with a signal-to-noise ratio >4 within
data subsets of duration 0.5-1.5day. We find that two (TIC 202354658
and TIC 69298924) of these ten sdB stars likely have white-dwarf
companions and set limits on companion masses for the other eight sdB
stars.
Description:
We have chosen 10 hot subdwarfs with previously reported p-mode
pulsations, observed by the Transiting Exoplanet Survey Satellite
(TESS, 600-1000nm, IV/39) during Cycle 3 (09/20/18-10/18/18) and/or
4 (10/18/18-11/15/18) using 20s cadence (USC) data to properly sample
minute-long p modes. We accessed the time-series data from the
Mikulski Archive for Space Telescopes (MAST).
TIC 69298924 (J08069+1527DR2 654866823401111168, GALEX J080656.7+152718)
was classified as an sdB star by Vennes+2011 (2011MNRAS.410.2095V 2011MNRAS.410.2095V).
Baran+2011 (J/A+A/669/A48) found it to be a hybrid pulsator and
detected two g-mode and two p-mode frequencies. Baran+2023 (J/A+A/669/A48)
analyzed Sector 44-46 (10/12/21-12/30/21) TESS USC data and detected
only four frequencies in the p-mode region. They suggested that f2,
f3, and f4 may be a rotationally split triplet. Assuming this
interpretation is correct the rotation period would equal 12.9days.
We applied the pulsation timing analysis only to frequency f3 since it
was the only significant frequency in individual data subsets. We also
analyze observations of it from Sector 71-72 (10/16/23-12/07/23).
TIC 202354658 (PG 1544+601, Gaia DR2 1627040062490757120) was classified
as an sdB star by Green+1986 (II/207A). Baran+2024 (2024A&A...686A..65B 2024A&A...686A..65B)
analyzed consecutive TESS Sector 48-51 (01/28/22-05/18/22) USC data
and detected eight pulsation frequencies identified as p-modes. Three
frequencies, f5, f6 and f7, indicate the possibility of being
rotationally split modes. Assuming the interpretation of a triplet is
correct, the rotation period would be 17.3days. Baran+2024 found two
other equally spaced frequency patterns among f1, f2, and f3, and f4,
f5, and f8, with both spacing equal to 2.0uHz. We also analyze
observations from Sector 58 (10/29/22-11/26/22), 75-78 (01/30/24-05/21/24),
82 (08/10/24-09/05/24), and 85 (10/26/24-11/21/24).
Objects:
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RA (2000) DE Designation(s)
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15 45 09.61 +59 55 05.0 TIC 202354658 = 2MASS J15450961+5955051
08 06 56.68 +15 27 19.9 TIC 69298924 = 2MASS J08065668+1527200
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig3a.dat 27 74 TIC 69298924 f3 amplitudes (Data behind Figure 3)
fig3oc.dat 31 74 TIC 69298924 f3 timing delay (Data behind Figure 3)
fig6af2.dat 27 274 TIC 202354658 f2 amplitudes (Data behind Figure 6)
fig6af5.dat 27 279 TIC 202354658 f5 amplitudes (Data behind Figure 6)
fig6ocf2.dat 32 271 TIC 202354658 f2 timing delay (Data behind Figure 6)
fig6ocf5.dat 32 275 TIC 202354658 f5 timing delay (Data behind Figure 6)
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See also:
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
II/207A : Palomar-Green catalog UV-excess stellar objects (Green+ 1986)
J/ApJS/61/569 : KPD UV-excess objects (Downes+, 1986)
J/A+A/513/A6 : NOT survey of subdwarf B stars (Ostensen+, 2010)
J/MNRAS/421/181 : EC 01541-1409 pulsations frequencies (Reed+, 2012)
J/A+A/562/A95 : Orbital solutions of eight close sdB binaries (Geier+, 2014)
J/ApJ/845/171 : Rapid. pulsating sdB stars search with GALEX (Boudreaux+, 2017)
J/A+A/611/A48 : Seven sdB eclipsing binaries data (Pulley+, 2018)
J/ApJ/859/145 : 20yr obs. of the spectr. binary EC 20117-4014 (Otani+, 2018)
J/MNRAS/489/1556 : K2 observations of binaries PHL 457 & EQ Psc (Baran+, 2019)
J/A+A/635/A193 : Catalogue of hot subdwarf stars DR2 (Geier, 2020)
J/MNRAS/495/2844 : Mode identif. in 3 pulsating hot subdwarfs (Sahoo+, 2020)
J/A+A/650/A205 : Search for transiting planets around sdBs (Van Grootel+, 2021)
J/ApJ/926/17 : 25yr observations of the sdB star AQ Col (Otani+, 2022)
J/A+A/669/A48 : South. short-period pulsating hot-subdwarf stars (Baran+, 2023)
J/MNRAS/519/2486 : Variab. & sdBs stars in NEH/SEH TESS FFI III (Sahoo+, 2023)
J/A+A/710/A280 : Wide sdB binaries parameters (Molina+, 2026)
Byte-by-byte Description of file: fig3a.dat fig6af2.dat fig6af5.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 d Time Median observation time, BJD-2,457,000.0
12- 19 F8.5 10-3 Amp Amplitude, ppt
21- 27 F7.5 10-3 e_Amp Uncertainty in Amp
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Byte-by-byte Description of file: fig3oc.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d Time Median observation time, BJD-2,457,000.0
13- 23 F11.7 s O-C Timing delay
25- 31 F7.5 s e_O-C Uncertainty in O-C
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Byte-by-byte Description of file: fig6ocf2.dat fig6ocf5.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d Time Median observation time, BJD-2,457,000.0
13- 23 F11.7 s O-C Timing delay
25- 32 F8.5 s e_O-C Uncertainty in O-C
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Robin Leichtnam [CDS] 10-Jul-2026