A Radio Changing-state Jet in the Narrow-line Seyfert 1 Galaxy J1105+1452

Le résumé fourni par la source

Abstract We report the discovery of a radio-quiet to radio-loud transition in the narrow-line Seyfert 1 galaxy J1105+1452. The source has undergone a long-term evolution from a radio-quiet state in the 1990s to a persistently radio-bright state after 2017. Post-2017 flux densities in the 0.8–7 GHz range cluster between 32 and 43 mJy, whereas the 144 MHz flux density is only 1.94 ± 0.23 mJy. This indicates strong low-frequency suppression from a compact, absorbed component. Modeling the radio spectral energy distribution with a synchrotron self-absorption model yields a turnover frequency ν p = 0.48 ± 0.03 GHz and a peak flux density S p = 38.9 ± 4.7 mJy. These parameters classify J1105+1452 as a megahertz peaked-spectrum source, consistent with the new episode of an early-stage compact jet. Under the assumption of equipartition, we derive an intrinsic physical radius R ∼ 0.68 pc and an average apparent expansion velocity β app ≈ 0.64. The observed brightness temperature T b ≈ 6.0 × 10 11 K necessitates a Doppler factor δ ≈ 12, implying a relativistic jet viewed at θ ≲ 5°. Despite the dramatic radio evolution, the X-ray spectrum remains stable and steep (Γ ≃ 3.0), suggesting that the X-ray emission remains dominated by the disk/corona, while the radio band has become jet dominated. Our results identify J1105+1452 as a rare radio changing-state NLSy1, providing a unique laboratory for studying the birth and early evolution of relativistic jets at high Eddington ratios.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.