We made simultaneous single-dish and very long baseline interferometer ( VLBI ) observations of a narrow-line Seyfert 1 galaxy ( NLS1 ) 1H 0323+342 , showing gamma-ray activity revealed by Fermi /LAT observations .
We found significant variation of the total flux density at 8 GHz on the time scale of one month by the single-dish monitoring .
The total flux density varied by 5.5 % in 32 days , which is comparable to the gamma-ray variability time scale , corresponding to the variability brightness temperature of 7.0 \times 10 ^ { 11 } K. The source consists of central and southeastern components on the parsec ( pc ) scale .
The flux of only the central component decreased in the same way as the total flux density , indicating that the short-term radio variability , and probably the gamma-ray emitting region , is associated with this component .
From the VLBI observations we obtained the brightness temperatures of greater than ( 5.2 \pm 0.3 ) \times 10 ^ { 10 } K , and derived the equipartition Doppler factor of greater than 1.7 , the variability Doppler factor of 2.2 , and the 8 GHz radio power of 10 ^ { 24.6 } W Hz ^ { -1 } .
Combining them we conclude that acceleration of radio jets and creation of high-energy particles are ongoing in the central engine , and that the apparent very radio-loud feature of the source is due to the Doppler-boosting effect , resulting in the intrinsic radio loudness to be an order of magnitude smaller than the observed values .
We also conclude that the pc-scale jet represents recurrent activity from the the spectral fitting and the estimated kinematic age of pc- and kpc-scale extended components with different position angle .