Long-Term Transit Timing Monitoring and Refined Light Curve Parameters   of HAT-P-13b
  We present 10 new transit light curves of the transiting hot Jupiter HAT-P-13b, obtained during two observational seasons by three different telescopes. When combined with 12 previously published light curves, we have a sample consisting of 22 transit light curves, spanning 1,041 days across four observational seasons. We use this sample to examine the recently observed large-amplitude transit timing variations (P\'al et al. 2011), and give refined system parameters. We find that the transit times are consistent with a linear ephemeris, with the exception of a single transit time, from UT 2009 Nov 5, for which the measured mid transit time significantly deviates from our linear ephemeris. The nature of this deviation is not clear, and the rest of the data does not show any significant transit timing variation. 
Benjamin J. Fulton, Avi Shporer, Joshua N. Winn, Matthew J. Holman,   Andr\'as P\'al, J. Zachary Gazak
astro-ph.EP