J/MNRAS/541/714 WASP-4 mid-transit times (Basturk+, 2025)
The orbit of WASP-4 b is in decay.
Basturk O., Kutluay A.C., Barker A., Yalcinkaya S., Southworth J.,
Barkaoui K., Wunsche A., Burgdorf M.J., Timmermans M., Jehin E.,
Tregloan-Reed J., Jaimes R.F., Hinse T.C., Duru B., Hitchcock J.,
Longa-Pena P., Rahvar S., Sajadian S., Bretton M., Selam S.O., Gillon M.,
Bonavita M., D'Ago G., Dominik M., Jorgensen U.G., Snodgrass C.,
Spyratos P., Mancini L.
<Mon. Not. R. Astron. Soc. 541, 714 (2025)>
=2025MNRAS.541..714B 2025MNRAS.541..714B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical
Keywords: methods: data analysis - techniques: photometric -
stars: fundamental parameters - stars: individual: WASP-4 -
planetary systems
Abstract:
WASP-4 b is a hot Jupiter exhibiting a decreasing orbital period,
prompting investigations into potential mechanisms driving its
evolution. We analysed 173 transit light curves, including 37 new
observations, and derived mid-transit timings with exofast, forming
the most extensive transit timing variation (TTV) data set for this
system. Adding 58 literature timings and removing unreliable data, we
constructed a TTV diagram with 216 points. Our analysis considered
linear, quadratic, and apsidal motion models, with the quadratic model
proving to be significantly superior in all model comparison
statistics. We found no significant periodic signals in the data. The
quadratic model allows us to infer a tidal quality factor of
Q'*r∼80000 from the orbital decay rate if this is due to stellar
tides. Theoretical considerations indicate that such efficient
dissipation is possible due to internal gravity waves in the radiative
core of WASP-4, but only in our models with a more evolved host star,
possibly near the end of its main-sequence lifetime, and with a larger
radius than the observed one. Our main-sequence models produce only
about a third of the required dissipation (Q'*r∼2-5x105).
Therefore, the observed orbital decay can only be explained by a
slightly larger or more evolved host, resembling the case for WASP-12.
Our findings highlight the need for further stellar modelling and
improvement in our current understanding of tidal dissipation
mechanisms driving orbital decay in close-in exoplanetary systems.
Description:
In this study, we compiled and analysed 37 complete transit light
curves of WASP-4b from the literature, excluding 7 from our TTV
analysis for various reasons. Additionally, we examined 41 light
curves from the ETD, with 5 eliminated from further analysis. We also
processed a total of 61 light curves acquired by TESS in four sectors
at a 2-min cadence, and incorporated 37 newly obtained observations
with three different telescopes, of which three were excluded
(Appendix B). In total, we analysed 158 light curves and homogeneously
determined mid-transit timings using exofast models, forming the most
extensive TTV data set for WASP-4b to date. Furthermore, we included
58 mid-transit timings from the literature derived from light curves
that were not directly accessible. As a result, our final TTV diagram
consists of 216 data points.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
23 34 15.08 -42 03 41.0 WASP-4 = TOI-232
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 102 37 Mid-transit times used in this study
tablea2.dat 40 61 Mid-transit times we derived from
TESS observations
tablea3.dat 133 41 Mid-transit times we derived from the light
curves in the Exoplanet Transit Database (ETD)
tablea4.dat 100 34 Mid-transit times we derived from
literature light curves
tablea5.dat 47 58 Mid-transit times we made use of directly
from the literature
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See also:
J/MNRAS/399/287 : Transiting planetary system WASP-4 (Southworth+, 2009)
J/ApJ/733/127 : Four transits of WASP-4b (Sanchis-Ojeda+, 2011)
J/MNRAS/490/4230 : Transiting planet WASP-4b (Southworth+, 2019)
J/ApJ/893/L29 : WASP-4 RVs + hot Jupiter predicted period changes
(Bouma+, 2020)
J/AJ/163/281 : Radial velocity, transit + occultation of WASP-4
(Turner+, 2022)
J/A+A/669/A124 : KELT-9 b, KELT-16 b, WASP-4 b and HD 97658 (Harre+, 2023)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date Observed date (UT)
12- 15 I4 d Epoch [1626/3045] Mid-transit timefromEXOFAST
(BJD_TDB)
17- 30 F14.6 d TcExofast [2458681.71/2460580.67] Mid-transit
timefromEXOFAST (BJD_TDB)
32- 38 E7.2 d e_TcExofast [0.0/0.01] Error of the mid-transit
timefromEXOFAST
40- 43 F4.2 --- Beta Red noise number
45- 48 F4.2 --- PNR Photon noise rate in ppt
50- 70 A21 --- Obser Name of the observatory
72 I1 --- Elim [0/1] Elimination of the data
(0:Included, 1:Eliminated)
74-102 A29 --- Just Justification of elimination
(see paper for details)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d TcExofast [2458355.18/2460205.96] Mid-transit time
from EXOFAST
16- 23 F8.6 d e_TcExofast [0.0/0.01] Error of the mid-transit time
from EXOFAST
25- 26 I2 --- Sector [2/69] TESS Sector Number
28- 31 F4.2 10-3 PNR Photon noise rate in ppt
33- 36 F4.2 --- Beta Red noise number
38 I1 --- Elim [0/1] Elimination of the data
(0: Included, 1: Eliminated)
40 A1 --- Just Justification of elimination
(see paper for details)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d TcExofast Mid-transit time from EXOFAST
16- 26 E11.6 d e_TcExofast Error of the mid-transit time from EXOFAST
28- 41 F14.6 d TcReported Mid-transit time reported by the observer
43- 47 E5.1 d e_TcReported Error of the mid-transit time reported by
the observer
49- 52 F4.2 --- Beta Red noise number
54- 57 F4.2 --- PNR Photon noise rate in ppt
59-101 A43 --- Observer Name(s) of the observer(s) as appeared in ETD
103 I1 --- Elim Elimination of the data
(0: Included, 1: Eliminated)
105-133 A29 --- Just Justification of elimination
(see paper for details)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d TcExofast Mid-transit time from EXOFAST
16- 22 E7.2 d e_TcExofast Error of the mid-transit time
24- 37 F14.6 d TcReported Mid-transit time reported by the observer
39- 45 E7.2 d e_TcReported Error of the mid-transit time reported
by the observer
47- 50 F4.2 --- Beta Red noise number
52- 55 F4.2 --- PNR Photon noise rate in ppt
57- 83 A27 --- Ref Literature Reference of the mid-transit
time (1)
85 I1 --- Elim Elimination of the data
(0: Included, 1: Eliminated)
87-100 A14 --- Just Justification of elimination
(see paper for details)
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Note (1): Reference as follows:
Harre et al. (2023) = 2023Univ....9..506H 2023Univ....9..506H
Sanchis-Ojeda et al. (2011) = 2011ApJ...733..127S 2011ApJ...733..127S
Southworth et al. (2019) = 2019MNRAS.490.4230S 2019MNRAS.490.4230S
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Byte-by-byte Description of file: tablea5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d TcReported Mid-transit time reported by the observer
16- 22 F7.5 d e_TcReported Error of the mid-transit time reported
by the observer
24- 47 A24 --- Ref Literature reference of the mid-transit
time (1)
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Note (1): References as follows:
Baluev et al. (2020) = 2020MNRAS.496L..11B 2020MNRAS.496L..11B
Dragomir et al. (2011) = 2011AJ....142..115D 2011AJ....142..115D
Gillon et al. (2009) = 2009A&A...496..259G 2009A&A...496..259G
Hoyer et al. (2013) = 2013MNRAS.434...46H 2013MNRAS.434...46H
Huitson et al. (2017) = 2017AJ....154...95H 2017AJ....154...95H
Ma et al. (2025) = 2021ApJ...918...16M 2021ApJ...918...16M
Nikolov et al. (2012) = 2012A&A...539A.159N 2012A&A...539A.159N
Ranjan et al. (2014) = 2014ApJ...785..148R 2014ApJ...785..148R
Southworth et al. (2011) = 2014MNRAS.444..776S 2014MNRAS.444..776S
Wilson et al. (2008) = 2008ApJ...675L.113W 2008ApJ...675L.113W
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Acknowledgements:
Ozgur Basturk, obasturk(at)ankara.edu.tr
(End) Patricia Vannier [CDS] 20-Oct-2025