Survey the Time Relation between Gamma-Rays and the Optical Light of Gamma-Ray Novae

In 2010, researcher detected gamma-rays from V407 Cyg for the first time through NASA’s Fermi Gamma-Ray Space Telescope. Since then, the gamma-ray counterpart of 17 novae have been detected. V906 Car is one of these 17 novae, and the multi-wavelength investigations of this target showed that the optical and gamma-ray light curves are tightly correlated with a time lag of 5 hours (led by the gamma-rays). However, it is unclear whether the similar feature can be observed in other gamma-ray novae. In this study, we aim to investigate whether other gamma-ray novae also exhibit a similar correlation by comparing the Fermi gamma-ray observations with the optical data of AAVSO and ASAN-SN. We use two different methods: (i) we bin the gamma-ray data with overlapping time regions in order to minimize the information lost during the binning process. We then shift the optical light curve with respect to the gamma-ray light curve and search for the possible time lag using the least square method; (ii) based on the distribution of the optical light curve with assumed time lags, we compute likelihood values of the time lags in respect to the Fermi-LAT light curve. Through these approaches, we seek to confirm whether a consistent connection exists between the optical and gamma-ray bands in other 17 gamma-ray novae.