The SOPHIE search for northern extrasolar planets

Abstract

Aims. Since 2011, the SOPHIE spectrograph has been used to search for Neptunes and super-Earths in the northern hemisphere. As part of this observational program, 290 radial velocity measurements of the 6.4 V magnitude star HD 158259 were obtained. Additionally, TESS photometric measurements of this target are available. We present an analysis of the SOPHIE data and compare our results with the output of the TESS pipeline. Methods. The radial velocity data, ancillary spectroscopic indices, and ground-based photometric measurements were analyzed with classical and ℓ1 periodograms. The stellar activity was modeled as a correlated Gaussian noise and its impact on the planet detection was measured with a new technique. Results. The SOPHIE data support the detection of five planets, each with m sin i ≈ 6 M⊕, orbiting HD 158259 in 3.4, 5.2, 7.9, 12, and 17.4 days. Though a planetary origin is strongly favored, the 17.4 d signal is classified as a planet candidate due to a slightly lower statistical significance and to its proximity to the expected stellar rotation period. The data also present low frequency variations, most likely originating from a magnetic cycle and instrument systematics. Furthermore, the TESS pipeline reports a significant signal at 2.17 days corresponding to a planet of radius ≈1.2 R⊕. A compatible signal is seen in the radial velocities, which confirms the detection of an additional planet and yields a ≈2 M⊕ mass estimate. Conclusions. We find a system of five planets and a strong candidate near a 3:2 mean motion resonance chain orbiting HD 158259. The planets are found to be outside of the two and three body resonances.

Six transiting planets and a chain of Laplace resonances in TOI-178

“…In this section, we consider the 46 ESPRESSO data points only and look for potential planet detections. Our analysis follows the same steps as in Hara et al (2020) and is described in detail in Appendix B. To search for potential periodicities, we computed the 1 -periodogram 8 of the RV as defined in Hara et al (2017).…”

“…Radial velocity signals found to be statistically significant might vary from one activity model to another. To confirm the robustness of our detections, we tested whether signal detections can be claimed for a variety of noise models, following Hara et al (2020). This approach consists of three steps.…”

“…TOI178 The signals found to be statistically significant might vary depending on the frequency grid, base, and noise models. To explore this aspect, as in Hara et al (2020), we computed the 1periodogram of the data with different assumptions regarding the noise covariance. We then ranked the covariance models via CV.…”

“…For planets that remained in resonance and are close enough to their host stars, tides become the dominant force that affects the architecture of the systems, which can then lead to a departure of the period ratio from the exact resonance (Henrard & Lemaitre 1983;Papaloizou & Terquem 2010;Delisle et al 2012). In some near-resonant systems, such as HD 158259, the tides seem to have pulled the configuration entirely out of resonance (Hara et al 2020). However, through gentle tidal evolution it is possible to retain a resonant state even with null eccentricities through three-body resonances (Morbidelli 2002;Papaloizou 2015).…”

Planetary system LHS 1140 revisited with ESPRESSO and TESS

“…We assumed a noise model with a white-noise component σ W , a calibration error σ C , and a Gaussian component with amplitude σ R and exponential decay τ. We then considered all possible combinations of values for σ R = 0.0 ,0.5, 1.0, 1.5, 2 m s −1 , σ W = 0.5, 1 m s −1 σ C = 0.1, 0.5, 0.75 m s −1 , and τ = 0.0, 1.0, 3.0, 6.0 d. All these noise models were ranked with cross validation, as in Hara et al (2020). In Fig.…”