Transit timing variations in the WASP-4 planetary system

Southworth, J.; Dominik, M.; Jørgensen, U. G.; Andersen, M. I.; Bozza, V.; Burgdorf, M.; D’Ago, G.; Dib, Sami; Jaimes, R. Figuera; Fujii, Yuri I.; Gill, Samuel; Haikala, L. K.; Hinse, T. C.; Hundertmark, M.; Khalouei, Elahe; Korhonen, H.; Longa-Peña, Penélope; Mancini, L.; Peixinho, N.; Rabus, M.; Rahvar, S.; Sajadian, Sedighe; Skottfelt, J.; Snodgrass, C.; Spyratos, Petros; Tregloan-Reed, J.; Unda-Sanzana, E.; Essen, C. von

doi:10.1093/mnras/stz2602

Cited by 40 publications

(48 citation statements)

References 57 publications

(65 reference statements)

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“…Bouma et al (2019) first reported an orbital period variation of WASP-4b using TESS and ground-based observations. Southworth et al (2019) confirmed that the period was decaying with additional ground-based observations and found a decay rate of 9.2 msec yr −1 . They found that orbital decay and apsidal precession could explain the TTVs after ruling out instrumental issues, stellar activity, the Applegate mechanism, and light-time effect.…”

Section: Introductionsupporting

confidence: 80%

Characterizing the WASP-4 system with TESS and radial velocity data: Constraints on the cause of the hot Jupiter's changing orbit and evidence of an outer planet

Turner,

Flagg,

Ridden-Harper

et al. 2021

Preprint

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Orbital dynamics provide valuable insights into the evolution and diversity of exoplanetary systems. Currently, only one hot Jupiter, WASP-12b, is confirmed to have a decaying orbit. Another, WASP-4b, exhibits hints of a changing orbital period that could be caused by orbital decay, apsidal precession, or the acceleration of the system towards the Earth. We have analyzed all data sectors from NASA's Transiting Exoplanet Survey Satellite together with all radial velocity (RV) and transit data in the literature to characterize WASP-4b's orbit. Our analysis shows that the full RV data set is consistent with no acceleration towards the Earth. Instead, we find evidence of a possible additional planet in the WASP-4 system, with an orbital period of ∼7000 days and M c sin(i) of 5.47 +0.44 −0.43 M Jup . Additionally, we find that the transit timing variations of all of the WASP-4b transits cannot be explained by the second planet but can be explained with either a decaying orbit or apsidal precession, with a slight preference for orbital decay. Assuming the decay model is correct, we find an updated period of 1.338231587±0.000000022 days, a decay rate of -7.33±0.71 msec year −1 , and an orbital decay timescale of τ = P/| Ṗ | = 15.77±1.57 Myr. If the observed decay results from tidal dissipation, we derive a modified tidal quality factor of Q = 5.1±0.9 ×10 4 , which is an order of magnitude lower than values derived for other hot Jupiter systems. However, more observations are needed to determine conclusively the cause of WASP-4b's changing orbit and confirm the existence of an outer companion.

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Section: Introductionsupporting

confidence: 80%

Characterizing the WASP-4 system with TESS and radial velocity data: Constraints on the cause of the hot Jupiter's changing orbit and evidence of an outer planet

Turner,

Flagg,

Ridden-Harper

et al. 2021

Preprint

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“…A concerted effort has been undertaken by various teams to combine TESS data with ground-based observations (Yao et al 2019;Cortés-Zuleta et al 2020;Edwards et al 2020) and K2 data (Ikwut-Ukwa et al 2020) to improve the orbital properties of known transiting planets. Additionally, unexpected variations in the transit times of WASP-4b were detected by Bouma et al (2019) and confirmed by Southworth et al (2019), and were later explained by acceleration effects of the WASP-4 system (Bouma et al 2020). Figure 6.…”

Section: Science From the Primary Missionmentioning

confidence: 83%

Science Extraction from TESS Observations of Known Exoplanet Hosts

Kane

Bean

Campante

et al. 2020

PASP

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Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

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“…Most of these data are identical to the data presented by B19. Twenty-two new times reported by Southworth et al (2019) are included. These transits were observed from the 3.58m New Technology Telescope and the Danish 1.54m telescope at La Silla, Chile, and the South African Astronomical Observatory 1.0m telescope.…”

Section: Observationsmentioning

confidence: 99%

WASP-4 Is Accelerating toward the Earth

Bouma

Winn

Howard

et al. 2020

ApJL

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The orbital period of the hot Jupiter WASP-4b appears to be decreasing at a rate of −8.64 ± 1.26 msec yr −1 , based on transit-timing measurements spanning 12 years. Proposed explanations for the period change include tidal orbital decay, apsidal precession, and acceleration of the system along the line of sight. To investigate further, we performed new radial velocity measurements and speckle imaging of WASP-4. The radial-velocity data show that the system is accelerating towards the Sun at a rate of −0.0422 ± 0.0028 m s −1 day −1 . The associated Doppler effect should cause the apparent period to shrink at a rate of −5.94 ± 0.39 msec yr −1 , comparable to the observed rate. Thus, the observed change in the transit period is mostly or entirely produced by the line-of-sight acceleration of the system. This acceleration is probably caused by a wide-orbiting companion of mass 10-300 M Jup and orbital distance 10-100 AU, based on the magnitude of the radial-velocity trend and the non-detection of any companion in the speckle images. We expect that the orbital periods of 1 out of 3 hot Jupiters will change at rates similar to WASP-4b, based on the hot-Jupiter companion statistics of Knutson et al. (2014). Continued radial velocity monitoring of hot Jupiters is therefore essential to distinguish the effects of tidal orbital decay or apsidal precession from line-of-sight acceleration.

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Transit timing variations in the WASP-4 planetary system

Cited by 40 publications

References 57 publications

Characterizing the WASP-4 system with TESS and radial velocity data: Constraints on the cause of the hot Jupiter's changing orbit and evidence of an outer planet

Characterizing the WASP-4 system with TESS and radial velocity data: Constraints on the cause of the hot Jupiter's changing orbit and evidence of an outer planet

Science Extraction from TESS Observations of Known Exoplanet Hosts

WASP-4 Is Accelerating toward the Earth

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