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Fang X.-S.,CAS National Astronomical Observatories | Fang X.-S.,University of Chinese Academy of Sciences | Gu S.-H.,CAS National Astronomical Observatories | Cheung S.-L.,Ho Koon Nature Education Cum Astronomical Center | And 3 more authors.
Research in Astronomy and Astrophysics | Year: 2010

The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here. We reconstruct the observed light curves with a two-starspot model by means of a light curve modeling technique, and find that the active regions shift oppositely along longitude on a time scale of one day. Combining with the observational data obtained by other groups, we discuss the evolution of spotted regions in the photosphere, and find that its starspots evolve not only on a short time scale but also on a long time scale. The pure chromospheric emissions for Ca IIHK and Hβ lines are derived by using the spectral subtraction technique. The variation of Ca IIHK lines' excess emission is spatially correlated to the starspot regions. There is no clear rotational modulation for the Hβ line's excess emission, probably due to the contamination of prominence emission. © 2010 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source


Fang X.-S.,CAS National Astronomical Observatories | Fang X.-S.,Chinese Academy of Sciences | Fang X.-S.,University of Chinese Academy of Sciences | Gu S.-H.,CAS National Astronomical Observatories | And 5 more authors.
Research in Astronomy and Astrophysics | Year: 2012

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 technique. 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 (T 1 = 7750 K) and Case B (T 1 = 5250 K). Our analyses 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., ΔB 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. © 2012 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source


Wang X.-B.,CAS National Astronomical Observatories | Wang X.-B.,Chinese Academy of Sciences | Gu S.-H.,CAS National Astronomical Observatories | Gu S.-H.,Chinese Academy of Sciences | And 7 more authors.
Research in Astronomy and Astrophysics | Year: 2013

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. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source


Wang X.-B.,Chinese Academy of Sciences | Gu S.-H.,Chinese Academy of Sciences | Cameron A.C.,University of St. Andrews | Wang Y.-B.,Chinese Academy of Sciences | And 4 more authors.
Astronomical Journal | Year: 2014

The transiting exoplanetary system WASP-11/HAT-P-10 was observed using the CCD camera at Yunnan Observatories, China from 2008 to 2011, and four new transit light curves were obtained. Combined with published radial velocity measurements, the new transit light curves are analyzed along with available photometric data from the literature using the Markov Chain Monte Carlo technique, and the refined physical parameters of the system are derived, which are compatible with the results of two discovery groups, respectively. The planet mass is Mp= 0.526 ± 0.019 MJ, which is the same as West et al.'s value, and more accurately, the planet radius R p= 0.999 is identical to the value of Bakos et al. The new result confirms that the planet orbit is circular. By collecting 19 available mid-transit epochs with higher precision, we make an orbital period analysis for WASP-11b/HAT-P-10b, and derive a new value for its orbital period, P = 3.72247669 days. Through an (O-C) study based on these mid-transit epochs, no obvious transit timing variation signal can be found for this system during 2008-2012. © 2014. The American Astronomical Society. All rights reserved.. Source


Sun L.-L.,Chinese Academy of Sciences | Sun L.-L.,University of Chinese Academy of Sciences | Gu S.-H.,Chinese Academy of Sciences | Wang X.-B.,Chinese Academy of Sciences | And 9 more authors.
Research in Astronomy and Astrophysics | Year: 2015

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. © 2015 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source

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