Short-Term Variability of PKS1510-089
  We searched a short-term radio variability in an active galactic nucleus PKS 1510-089. A daily flux monitoring for 143 days at 8.4 GHz was performed, and VLBI observations at 8.4, 22, and 43 GHz were carried out 4 times during the flux monitoring period. As a result, variability with time scale of 20 to 30 days was detected. The variation patterns were well alike on three frequencies, moreover those at 22 and 43 GHz were synchronized. These properties support that this short-term variability is an intrinsic one. The Doppler factor estimated from the variability time scale is 47. Since the Doppler factor is not extraordinary large for AGN, such intrinsic variability with time scale less than 30 days would exist in other AGNs. 
Akiko Kadota, Kenta Fujisawa, Satoko Sawada-Satoh, Kiyoaki Wajima, and   Akihiro Doi
astro-ph.HE