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Long-term transit timing monitoring and homogenous study of WASP-32

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Research in Astronomy and Astrophysics 2015年第1期15卷 117-126页

作者： Lei-Lei Sun Sheng-hong Gu Xiao-Bin Wang Andrew Collier Cameron Dong-Tao Cao Yi-Bo Wang Yue Xiang ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung Leung Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences School of Physics and Astronomy University of St Andrews North Haugh St Andrews Fife KY16 9SS UK ho koon nature education cum astronomical centre hong Kong astronomical Society

We report new photometric observations of the transiting exoplanetary system WASP-32 made by using CCD cameras at Yunnan Observatories and ho koon nature education cum astronomical centre, China from 2010 to 2012. Following our usual procedure, the observed data are corrected for systematic errors according to the coarse decorrelation and SYSREM algorithms so as to enhance the signal of the transit events. Combined with radial velocity data presented in the literature, our newly observed data and earlier photometric data in the literature are simultaneously analyzed to derive the physical parameters describing the system by employing the Markov chain Monte Carlo technique. The derived parameters are consistent with the result published in the original paper about WASP-32b, but the uncertainties of the new parameters are smaller than those in the original paper. Moreover, our modeling result supports a circular orbit for WASP-32b. Through the analysis of all available mid-transit times, we have refined the orbital period of WASP-32b; no evident transit timing variation is found in these transit events.

关键词： techniques: photometric transiting exoplanetary system individual: WASP-32

A newly discovered active contact binary in the field of NGC 1348

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Research in Astronomy and Astrophysics 2012年第1期12卷 93-103页

作者： Xiang-Song Fang Sheng-hong Gu ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung Leung National astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China hokoon nature education cum astronomical centre Sik Sik-Yuen Hong Kong China hong Kong astronomical Society Hong Kong China

We present a CCD photometry study of a newly discovered active eclipsing binary in the field of open cluster NGC 1348 based on the first time-series photometric observation. From the minimum times, we determined an orbital period of P = 0.691363 d. Among our datasets, the BV（.RI）c light curves obtained in November 2008 were analyzed using the Wilson-Devinney light curve modeling tech- nique. Because of the uncertainty of the membership of this binary in open cluster NGC 1348, we have analyzed the photometric data in two cases with different primary effective temperatures： Case A （T1 = 7750K） and Case B （T1 = 5250K）. Our anal- yses reveal that, for Case A, it is a deep （f 〉 70%）, very low mass ratio （q - 0.096） binary system, indicating that it is now in the late evolution stage of a contact binary; while for Case B, it is a red system with extraordinarily long orbital period with respect to the period-color relation for normal contact binaries, which suggests that this binary has evolved off the main sequence. The well known O＇Connell effect （e.g., AB 0.03 mag） was found in the dataset obtained in November 2008, which could be due to the existence of starspots on the components, therefore the corresponding spot properties （for Case A： hot spot; for Case B： dark spot） were determined using the Wilson-Devinney code. With the purpose of analyzing the dark spot activity for Case B, we compared the light curves derived in different observing runs, and found that a slight change appeared from November to December, 2008, which indicates the evolution of spot activity on at least one component over a time scale of about one month.

关键词： stars: binaries: close -- stars: binaries: eclipsing -- stars: spots

The refined physical parameters of transiting exoplanet system HAT-P-24

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Research in Astronomy and Astrophysics 2013年第5期13卷 593-603页

作者： Xiao-Bin Wang Sheng-hong Gu Andrew Collier Cameron hong-Bo Tan ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung National astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences School of Physics and Astronomy University of St Andrews North Haugh St Andrews Fife KY16 9SS UK University of Chinese Academy of Sciences hokoon nature education cum astronomical centre Sik Sik Yuen hong Kong astronomical Society

The transiting exoplanet system HAT-P-24 was observed by using CCD cameras at Yunnan Observatory and hokoon astronomical centre, China in 2010 and 2012. In order to enhance the signal to noise ratio of transit events, the observed data are corrected for systematic errors according to Collier Cameron et al.＇s coarse de- correlation and Tamuz et al.＇s SYSREM algorithms. Three new complete transit light curves are analyzed by means of the Markov chain Monte Carlo technique, and the new physical parameters of the system are derived. They are consistent with the old ones from the discovered paper except for a new larger radius Rp = 1.364 Rj of HAT- P-24b, which confirms its inflated nature. By combining the five available epochs of mid-transit derived from complete transit light curves, the orbital period of HAT-P- 24b is refined to P = 3.3552479 d and no obvious transit timing variation signal can be found from these five transit events during 2010-2012.

关键词： exoplanet system -- transit -- individual: HAT-P-24