Speaker： Fabo Feng,  Postdoc at Carnegie Institution of Washington, USA         

Time： 9:00   April 6, 2020 (Monday) (Shanghai time)          

Host: Prof. Dong LaiZoom link：https://zoom.com.cn/j/580729099 (Meeting ID: 580729099;  Meeting code: 289948)

Abstract:

Since the discovery of the first exoplanet around a Sun-like star in 1995, thousands of exoplanets have been detected in the past decades. However, none of them are like our Earth, which is a temperate rocky planet orbiting around a G star. Although a few high precision spectrographs were recently designed to detect sub-m/s radial velocity (RV) signals caused by Earth twins, the current RV modeling is not precise enough for the detection of such small signals. First, previous noise modeling does not choose optimal noise models through model comparison and thus suffer from overfitting or underfitting problems. Second, barycentric correction used in RV data reduction ignores the coupling between the Earth's motion and the stellar reflex motion, ignores the chromatic aberration and relativistic effects in the target system, and suffers from astrometric errors and errors in Earth's ephemeris. To avoid these problems, I have developed the Agatha and PEXO algorithms to mitigate correlated noise caused by stellar activity, instrument and atmosphere by choosing optimal noise models in the Bayesian framework, and to model the motions of the Earth and the target system as well as relativistic effects in them comprehensively. PEXO is able to model timing to nanosecond, astrometry to μas, and RV to μm/s. It will be used to synthesize astrometric, RV, timing and photometric data in order to detect Earth twins and exomoons. PEXO is also able to test general relativity in binary stars and to detect gravitational waves in pulsar timing data. 

Bio:

Fabo got his bachelor's degree from Wuhan University and master's degree from Nanjing University. He obtained his PhD from the Max Planck Institute for Astronomy in Heidelberg, Germany. From 2015 to 2018, he conducted his postdoctoral research on exoplanets at the University of Hertfordshire in England. Since November of 2018, he has been working with Dr. Paul Butler to continue exoplanet hunt at the Carnegie Institution for Science in Washington, DC, USA. He has developed many algorithms and methods to detect exoplanets using the radial velocity method. He has discovered more than 20 exoplanets such as super-Earths around tau Ceti and has helped to discover planets around nearby stars such as Barnard's star and Proxima Centauri. His recent work is focused on developing the PEXO software to analyze high precision data in order to find Earth twins.