WASP-4 transit timing variation from a comprehensive set of 129 transits

Abstract

We homogeneously reanalyse 124 transit light curves for the WASP-4 b hot Jupiter. This set involved new observations secured in 2019 and nearly all observations mentioned in the literature, including high-accuracy GEMINI/GMOS transmission spectroscopy of 2011–2014 and TESS observations of 2018. The analysis confirmed a non-linear transit timing variation (TTV) trend with $P/|\dot{P}|\sim \hbox{17-30}$ Myr (1σ range), implying only half of the initial decay rate estimation. The trend significance is at least 3.4σ in the aggressively conservative treatment. Possible radial acceleration due to unseen companions is not revealed in Doppler data covering seven years 2007–2014, and radial acceleration of −15 m s−1 yr−1 reported in a recent preprint by another team is not confirmed. If present, it is a very non-linear radial velocity variation. Assuming that the entire TTV is tidal in nature, the tidal quality factor $Q_\star ^{\prime }\sim \hbox{(4.5-8.5)}\times 10^4$ does not reveal a convincing disagreement with available theory predictions.

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

“…Our finding that the constant-period model does not fit the data well is consistent with previous studies (Bouma et al 2019;Southworth et al 2019;Baluev et al 2020). The orbital decay and apsidal precession models fit the data with a minimum chi-squared (χ 2 min ) of 276.35 and 270.42, respectively.…”

“…Bouma et al (2020) obtained additional radial-velocity (RV) data on WASP-4b using HIRES on Keck and found that the observed orbital period variation could be explained by the sys-tem accelerating toward the Sun at a rate of -0.0422 m s −1 day −1 . Recently, Baluev et al (2020) analyzed a comprehensive set of 129 transits and additional RV data (presented in Baluev et al 2019) from 2007-2014 (mostly in years not covered by the RV data presented in Bouma et al 2020). They also confirmed a period change in WASP-4b's orbit but do not confirm the RV acceleration found by Bouma et al (2020).…”

“…Cáceres et al 2011;Ranjan et al 2014;Bixel et al 2019) and orbital parameters (e.g. Southworth 2009;Winn et al 2009a;Hoyer et al 2013;Baluev et al 2020) have been studied extensively since its discovery in 2008. Bouma et al (2019) first reported an orbital period variation of WASP-4b using TESS and ground-based observations.…”

Discovery and characterization of the exoplanets WASP-148b and c

“…They include stellar activity, tide-caused orbital decay, or additional companions. In the case of WASP-4, Bouma et al (2020) recently showed that it could be mostly or entirely produced by the line-of-sight acceleration of the system (see, however, Baluev et al 2020). The third case is WASP-47b, a hot Jupiter on a 1.1 d period showing TTVs of half a minute that are explained by two smaller short-period planets (Becker et al 2015, Weiss et al 2017.…”

First steps to mapping of exoplanets: modeling secondary eclipses and search inhomogeneities in the infrared brightness profiles

“…Коэффициенты многочленов, моделирующих звездную активность, подбирались отдельно для каждого затмения, а доля потока от планеты в общем потоке и смещение центра затмения -относительно расчетного для всех. Решение этой задачи происходило по аналогии с работой [6]. Для реализации метода наименьших квадратов использовалась функция optimize.curve_fit из пакета scipy [7].…”