ZTF Monitoring of $\gamma-$ray emitting Narrow Line Seyfert 1 Galaxies

TL;DR

This study analyzes long-term optical variability of gamma-ray-emitting narrow-line Seyfert 1 galaxies using ZTF data, revealing variability patterns, timescales, and disc-jet connection signatures consistent with blazar-like behavior.

Contribution

It provides the first detailed long-term optical variability analysis of gamma-ray NLSy1 galaxies, linking variability timescales to physical processes and black hole mass.

Findings

Fractional variability up to 72% observed.

Color-magnitude trends similar to blazars.

Characteristic variability timescales correlated with black hole mass.

Abstract

The $\gamma$-ray-emitting narrow-line Seyfert-I ($\gamma$-NLSy1) are among the most interesting systems for studying disk-jet coupling. The soft X-ray properties of these systems suggest the presence of a disc component, which peaks in the optical/UV regime, in addition to the active jet. In this work, we investigate the optical emission from $\gamma$-NLSy1 using long-term Zwicky Transient Facility (ZTF) observations and discussed in the context of blazars. We have reported the long-term flux and color variability in the g- and r-bands. The fractional variability ($F_{\rm var}$) goes as high as 72\%, with a mean value of 23\%, while the amplitude of variability ($\psi$) values range from 0.24 to 3.20, which is consistent with the long-term Swift-UVOT variability studies. The color-magnitude diagrams exhibit an RWB or BWB trend similar to that of blazars. The $t_{\rm var}$ suggests an emitting region size of $10^{15-17}$ cm, aligned with emissions coming from the inner accretion disk or base of the jet. The PSD analysis using both DRW and CARMA modeling exhibits a characteristic break timescale of a few days to hundreds of days, which is likely linked to fundamental physical timescales in the system, such as thermal or viscous timescales in the accretion disk or timescales for acceleration and energy dissipation in the jet. The existence of these timescales acts as another signature of the disc-jet connection. These time scales are correlated with black hole mass, and the relation is consistent with previous studies.