The observation of exoplanet transit events in China

Xiao-bin Wang1, Sheng-hong Gu1, Andrew Collier Cameron2, Xiang-song Fang1, Dong-tao Cao1 and Zhi-liang Guo1

1.Yunnan Observatory, CAS, China2.University of St. Andrews, UK

Shanghai 2009.07.21

Outline

Background Observation Data reduction Light curve analysis Future plan

Background

It is known well that the transit of exoplanet can provide information about its radii and orbital inclination which can be used to derive its mass and density, furthermore, to infer the clue on its formation and evolution.

The monitoring for changes on orbital inclination, transit time and duration makes it possible to detect other low-mass exoplanets.

Here, we give out the preliminary results of our follow-up observation on transit events and future plan on this topic in China.

Observation Instruments

1.0m telescope+2Kx2K CCD at Yunnan Observatory

R filter

85cm telescope+1Kx1K CCD at Xinglong station of NAOC.

R filter

Targets: SuperWASP project: WASP-1b, WASP-2b, WAS

P-11b… XO project: XO-2b, XO-3b… HATNet project: HAT-P-1b, HAT-P-9b… CoRoT project: CoRoT-Exo-1b…

Data reduction

Photometry Aperture photometry (uncrowded field)

IRAF package Image subtraction (crowded field)

ISIS package (Alard & Lupton 1998, Alard 2000)

Two examples

Remove the systematic errors for aperture photometry results Coarse decorrelation (Collier Cameron et al. 200

6) SysRem algorithm (Tamuz et al. 2005)

WASP-11b

XO-2b

Light curve analysis

Markov Chain Monte Carlo code (Collier Cameron et al. 2007)

Result 1: WASP-11b

Transit epoch=2454793.18411+0.00018-0.00018

Transit depth=0.0217+0.0002-0.0003mag

Transit width=0.09579+0.00072-0.00342days

Stellar mass=0.77+0.01-0.007M_sun

Stellar radius=0.81+0.01-0.006R_sun

Orbital inclination=89.976+ -0.241 -0.749 degPlanet radius=1.02+0.01

-0.009R_jup

Result 2: XO-2b

Transit epoch=2454804.32478+0.00021-0.00027

Transit depth=0.0132+0.0006 - -0.0001 mag

Transit width=0.09853+ -0.00266 -0.01995 days Stellar mass=0.968+0.014 -0.008 M_sun Stellar radius=0.975+0.011

-0.006R_sun Orbital inclination=88.982+ -0.443 -1.616 deg Planet radius=0.955+0.028 - -0.002 R_jup

Future plan New instruments

Lijiang 2.4m telescope CCD camera: 2Kx2K chip, FOV 4’x4’ YFOSC CCD camera: 4Kx4K chip, FOV 9’X9’ Mosaic CCD camera: 6Kx6K, 4chips, FOV 9’x9’ LiJET: LiJiang Exoplanet Tracker (see Ting-gui Wang’s tal

k yesterday)

Research projects Defocus observation for transit events

Improve the accuracy of transit light curves Open cluster transit survey

Discover new transit exoplanet candidates LiJET follow-up confirmation for the brighter ones of the

m

Thank you!