Unraveling the mysteries of Jets in peculiar NLSy1 galaxies through multi-wavelength variability

Abstract

Radio-quiet narrow-line Seyfert 1 galaxies (RQ-NLSy1s) are generally considered to be dominated by thermal emission from the accretion disk. However, recurring 37 GHz radio flares detected from seven RQ-NLSy1s by the Metsahovi Radio Observatory suggest that non-thermal processes may also contribute to their emission. We present a systematic optical and mid-infrared (MIR) variability study combined with broadband SED modeling to investigate the origin of their flux variations and assess the relative contributions of accretion disk and possible jet-related components. High-cadence optical light curves in the g, r, and i bands were obtained from ZTF, while long-term MIR light curves in the W1 and W2 bands were taken from WISE. Optical variability was quantified using the FAGN-test, peak-to-peak variability amplitude, and fractional variability, while MIR variability was characterized using redshift-corrected intrinsic variability amplitudes. Optical variability was examined from intra-night to long-term timescales, and MIR variability on long-term timescales. All RQ-NLSy1s show statistically significant long-term optical variability, with amplitudes increasing toward shorter wavelengths. Three sources exhibit bluer-when-brighter trends and increasing variability amplitudes across the optical bands, indicating a non-thermal contribution. Intrinsic MIR variability is detected in three of the four sources. Significant optical-MIR and MIR intra-band lags are observed, while optical intra-band lags are insignificant. Optical variability amplitudes are anti-correlated with the Eddington ratio and positively correlated with black hole mass. These results suggest that a subset of RQ-NLSy1s hosts weak or intermittent jets contributing to their optical and MIR emission, supported by SED modeling. Coordinated multi-wavelength monitoring is required to better constrain the origin of these variations.

Figures (16)

• Figure 1: Long-term r-band ZTF light curves of the seven RQ-NLSy1s from the current sample, showing variability (V) from all the sources on a year-like timescale. The name and long-term variability status of each RQ-NLSy1 galaxy are presented in the title of each panel, and estimated variability parameters $\psi_{\mathrm{pp}}$ and $F_\mathrm{var}$ are displayed in the upper-left corner of each panel.
• Figure 2: Long-term WISEW1 and W2 light curves for the RQ-NLSy1s J122844.81$+$501751.2, J123220.11$+$495721.8, J150916.18$+$613716.7, and J164100.10$+$345452.7 from the current sample, which have reliable MIR measurements. All sources exhibit significant variability in both bands, except for J122844.81$+$501751.2, which shows no clear long-term variation. The name and long-term variability status of each source are indicated in the title of each panel, and the estimated redshift-corrected intrinsic variability amplitude, $V_{mz}$, is shown in the upper-left corner.
• Figure 3: ZTFr-band light curves of the RQ-NLSy1s J102906.69$+$555625.2, J122844.81$+$501751.2, and J123220.11$+$495721.8 from the current sample, covering intra-night to month-like timescales. All sources exhibit significant non-variability (NV) on all timescales except for J123220.11$+$495721.8, which shows variability only on month-like timescales. The name and analyzed timescale for each source are given in the panel title. Estimated variability parameters, $\psi_{\mathrm{pp}}$ and $F_\mathrm{var}$, along with the variability status and duration of each light curve, are indicated in the upper-left and upper-right corners of the respective panels.
• Figure 4: (Continued) Same as Fig. \ref{['fig: Intranight_optical_variability_1']} but for RQ-NLSy1s J150916.18$+$613716.7, J151020.06+554722.0, J152205.41+393441.3, and J164100.10$+$345452.7, respectively. All four sources are exhibiting variability on all timescales except for RQ-NLSy1s J150916.18$+$613716.7 and J151020.06+554722.0, which do not show variability on the intra-night timescale.
• Figure 5: Long-term ($\emph{g-r}$) color variations versus $\emph{r}$-magnitude, $\emph{g}$-magnitude, and $\emph{(g+r)}$ for the RQ-NLSy1s J102906.69$+$555625.2 (top), J122844.81$+$501751.2 (middle), and J123220.11$+$495721.8 (bottom) from the current sample. Significant positive trends are observed in J102906.69$+$555625.2 and J123220.11$+$495721.8 across all color–magnitude combinations. The black dashed line shows the best fit obtained using orthogonal distance regression, accounting for uncertainties in both color and magnitude. The corresponding slope and Pearson-$\rho$ are indicated in the upper-left corner of each panel.