Abstract
Magnetars are neutron stars powered by strong magnetic field (B > $10^{14}G$). Their spin period is in the range of 2 - 12s. The magnetic stress in the star may distort the crust (observed as outbursts), so magnetars (especially in outbursts) may emit gravitational waves. There are 29 magnetars known (potential gravitational waves sources), and increasing the number will increase the chance of detecting low-frequency gravitational waves. In addition, magnetars can be used for studying matter under extreme condition. In this study, we searched for more magnetars using extensive Chandra archival data and found 11 candidates. Due to the limited sensitivity of Chandra, form identification cannot be made, and more sensitivity X-ray data are needed.