Title: 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 from the Sun. Recently, radial
velocity observations revealed the existence of an Earth-mass planet around it.
With an orbital period of ~11 days, the surface of Proxima Centauri b is
temperate and might be habitable. We took 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 8th,
is identified tentatively. Its midtime, $T_{C}=2,457,640.1990\pm0.0017$ HJD, is
consistent with the predicted ephemeris based on RV orbit in a 1$\sigma$
confidence interval. Time-correlated noise is pronounced in the light curve of
Proxima Centauri, affecting detection of transits. We develop a technique, in a
Gaussian process framework, to gauge the statistical significance of potential
transit detection. The tentative transit signal reported here, has a confidence
level of $2.5\sigma$. Further detection of its periodic signals is necessary to
confirm the planetary transit of Proxima Centauri b. We plan to monitor Proxima
Centauri in next Polar night at Dome A in Antarctica, taking the advantage of
continuous darkness. \citet{Kipping17} reported two tentative transit-like
signals of Proxima Centauri b, observed by the Microvariability and Oscillation
of Stars space Telescope in 2014 and 2015, respectively. The midtransit time of
our detection is 138 minutes later than that predicted by their transit
ephemeris. If all 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.