Work

Unraveling the mysteries of jets in peculiar NLSy1 galaxies through multiwavelength variability

Year: 2026

Type: article

Abstract: Context. Radio-quiet narrow-line Seyfert 1 galaxies (RQ-NLSy1s) are generally considered to be dominated by thermal emission from the accretion disk. However, detections of recurring flaring at 37 GHz by the Metsähovi Radio Observatory from seven RQ-NLSy1s suggest that nonthermal processes may also contribute to their observed emission. Aims. We performed a systematic optical and mid-infrared (MIR) variability study along with broadband spectral energy distribution (SED) modeling of these seven RQ-NLSy1s to investigate the origin of their flux variations and assess the relative contributions of the accretion disk and potential jet-related components. Methods. High-cadence optical light curves in the g , r , and i bands were obtained from the Zwicky Transient Facility (ZTF), and long-term MIR light curves in the W1 and W2 bands were obtained from the Wide Field Infrared Survey Explorer. Optical variability was quantified using the F AGN test, peak-to-peak variability amplitude ( ψ pp ), and fractional variability ( F var ), while MIR variability was characterized by the redshift-corrected intrinsic variability amplitude. Optical variability was examined on timescales from intra-night to long-term, and MIR variability on long-term timescales. Color–magnitude behavior was analyzed using bias-resistant representations, and correlations with the physical parameters of active galactic nuclei (AGNs) were explored. Results. All seven sources exhibit statistically significant long-term optical variability, with variability amplitudes systematically increasing toward shorter wavelengths on the investigated timescales. In three sources, exhibiting pronounced bluer-when-brighter trends, both ¯ ψ pp and ¯ F var increase across the ZTF bands, a behavior that can also arise from accretion-disk variability. Together with the observed sub-timescale variability, these values support a nonthermal contribution. Intrinsic MIR variability is detected in three of the four sources. Significant optical–MIR and MIR intra-band lags are observed, while intra-band optical lags are not statistically significant in the sample. Optical variability amplitudes are anticorrelated with the Eddington ratio and emission-line ratios and positively correlated with black hole mass. Conclusions. A subset of RQ-NLSy1s exhibits variability patterns similar to those observed in jet-dominated AGNs, suggesting that weak or intermittent jets contribute to their optical and MIR emission. Independently of these variability diagnostics, a full-baseline Fermi-LAT analysis yields significant (≥5 σ ) GeV detections for all six SED-modeled sources, while the corresponding broadband SED modeling requires a nonthermal, jet-related emission component in these objects. Although the inferred jet conditions are similar to those of blazars, the faint GeV emission and absence of persistent radio jets indicate low-power and/or intermittent jets. Coordinated multiwavelength monitoring is nevertheless required to further constrain the physical origin of the observed variability.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202659385