Preliminary results of solving the problem of geometric distortion for the 2.4 m telescope at Yunnan Observatory

We observed the open clusters NGC 1664 （43 exposures） and M35 （42 ex- posures） by the Yunnan Faint Object Spectrograph and Camera in the 2.4 m telescope at Yunnan Astronomical Observatory on 2011 January 3, and processed them by a method recently proposed by us. The result shows that there is a geometric distortion effect in the field of view and the maximum distortion is - 0.25 （i.e. 1 pixel）. After correcting the geometric distortion, the precision of stellar positional measurement is significantly improved. The best precision in each direction is 6 mas for well-exposed stars.

The updated Bulk Lorentz Factors of Gamma-Ray Burst X-Ray Flares

X-ray flares are the most common phenomena in the afterglow phase of gamma-ray bursts （GRBs） in the Swift era, and are known as a canonical component in X-ray afterglows. In this work, we constrain the Lorentz factor of X-ray flares with an updated sample. We extensively search for X-ray light curves showing flare and jet break simultaneously. A smooth broken power law function is used to fit the jet breaks in 11 GRBs. We also use a smooth broken power law function to fit the profile of X-ray flares, and the total number of the flares is 20. We obtain the lower and upper limits of Lorentz factor （Гx） with the timescale, half-opening angle and mean luminosity of the X-ray flares for interstellar medium （ISM） and wind cases. The lower limits on Px range from tens to a few hundred, and the upper limits are mainly about a few hundred. We also apply the limited Lorentz factor to test correlations of Г0 - γ,iso and Г0 - Lγ,iso for GRBs, and find X-ray flares in the ISM case are much more consistent with those of prompt emission than the wind case in a statistical sense for both correlations. X-ray flares are almost consistent with the trend in the correlations of Г0 - Eγ,iso（Lγ,iso） for prompt GRBs, indicating X-ray flares and prompt bursts may have the same physical origin.

Short-range correlation effects in neutron star's radial and non-radial oscillations

In this study,we determine the influence of the nucleon-nucleon short range correlation(SRC)on static spherically symmetric neutron stars(NSs)from the perspectives of radial and nonradial oscillations for the first time.We revise the equation of state and coupling parameters in the relativistic mean field theory after considering the SRC effect,and select the hyperon coupling parameters as the SU(3)model.For the non-radial oscillations,the SRC effect decreases the f-mode frequency by 0.2~0.3 kHz.For the radial oscillations,it decreases the fundamental radial frequency f_(1) by 0.75~0.85 kHz.Additionally,we refit the linear relationship between the average density and f-mode frequency for SRC.Combining the characteristics of the radial and non-radial frequencies,we provide a view of inferring the maximum mass of NSs.Owing to the characteristics of the SRC influence on the radial frequency,we expect that the SRC can be tested by future observation and can also be used as a probe for the structure inside NSs.