A long-term look into variability and duty cycle of gamma-ray narrow-line Seyfert 1s with Swift

Gamma-ray narrow-line Seyfert 1 galaxies (gNLS1s) are now well-established as part of the family of jetted active galactic nuclei. After their discovery in 2009, their number has steadily increased, but they are still usually observed as a response to flares in the gamma-ray energy band. Therefore, in order to investigate the long-term behaviour of such kind of sources, we performed year-long Swift monitoring campaigns with weekly observations on four prominent gNLS1s which include the best candidates for detection by the Cherenkov Telescope Array Observatory, namely SBS 0846+513, PKS 1502+036, FBQS J1644.9+2619, and PMN J0948+0022 (with the latter recently being re-classified as an intermediate Seyfert, and hence providing a control case). Our campaigns offer, for the first time, a systematic study of gNLS1s without the bias of ToO observations triggered from gamma-ray flares, thus providing an investigation of their intrinsic properties. Our Bayesian blocks analysis of the long-term monitoring light-curves yields an estimate not only of variability but also the duty cycle of the gNLS1 and the expected number of flares per year.