Searching for the Transit of the Earth-mass Exoplanet Proxima Centauri b in Antarctica: Preliminary Result

Abstract

ProximaCentauri is known as the closest star to the Sun. Recently, radial velocity (RV) observations revealed the existence of an Earth-mass planet around it. With an orbital period of ∼11 days, Proxima Centauri b is probably in the habitable zone of its host star. We undertook a photometric monitoring campaign to search for its transit, using the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. A transit-like signal appearing on 2016 September 8 has been tentatively identified. Its midtime, T C =2,457,640.1990±0.0017 HJD, is consistent with the predicted ephemeris based on the RV orbit in a 1σ confidence interval. Time-correlated noise is pronounced in the light curve of ProximaCentauri, affecting the detection of transits. We develop a technique, in a Gaussian process framework, to gauge the statistical significance of a potential transit detection. The tentative transit signal reported here has a confidence level of 2.5σ. Further detection of its periodic signals is necessary to confirm the planetary transit of ProximaCentaurib. We plan to monitor ProximaCentauri in the next polar night at DomeA in Antarctica, taking advantage of continuous darkness. Kipping et al. reported two tentative transit-like signals of ProximaCentaurib observed by the Microvariability and Oscillation of Stars space telescope in 2014 and 2015. The midtransit time of our detection is 138minutes later than that predicted by their transit ephemeris. If all of the signals are real transits, the misalignment of the epochs plausibly suggests transit timing variations of ProximaCentaurib induced by an outer planet in this system.

3-D climate simulations for the detectability of Proxima Centauri b

“…A planet in the habitable zone of Proxima Centauri was detected in Anglada-Escudé et al (2016) and confirmed recently in Damasso et al (2020) and Suárez Mascareño et al (2020). The planet, known as Proxima b, has not been observed as a transiting planet (Davenport et al 2016;Kipping et al 2017;Liu et al 2018;Blank et al 2018;Feliz et al 2019;Jenkins et al 2019) and the estimated geometric probability of a transit is about 1.5%, (Anglada-Escudé et al 2016). As a consequence, constraints can exclusively be set on the orbit semi-major axis and on the planet's revolution period, leaving mass, radius, and density of the planet to be assumed.…”

Toward Extremely Precise Radial Velocities: II. A Tool For Using Multivariate Gaussian Processes to Model Stellar Activity

“…One kernel function that has been used to model stellar variability (specifically in stellar photometry, see Liu et al (2018); Littlefair et al (2017); Aigrain et al (2012Aigrain et al ( , 2015) is the squared exponential (SE) kernel ( 16).…”

No Transits of Proxima Centauri Planets in High-Cadence TESS Data

“…They found inconclusive evidence for transits of planet b, and they also found an additional transit candidate that was inconsistent with the transit window of Proxima b, perhaps indicating an additional planet. Liu et al (2018) used the Bright Star Survey Telescope at the Zhongshan Station in Antarctica to observe Proxima Centauri, conducting a 10-days long photometric monitoring campaign in 2016. This work also detected a transit-like signal consistent with the RV orbital parameters of planet b, but were unable to definitively confirm a transit of Proxima b.…”