Swift follow-up of the gamma-ray flaring NLSy1 1H 0323+342
ATel #17411; F. D'Ammando (INAF-IRA Bologna), F. Longo (University of Trieste and INFN Trieste), A. Holzmann Airasca (University of Trento and INFN Bari) and G. La Mura (INAF - Astronomical Observatory of Cagliari)
on 22 Sep 2025; 11:25 UT
Credential Certification: Filippo D'Ammando (dammando@ira.inaf.it)
Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, >GeV, Request for Observations, AGN, Black Hole, Blazar
Referred to by ATel #: 17423
Following the gamma-ray flaring activity of the narrow-line Seyfert 1 galaxy 1H 0323+342 (also known as 4FGL J0324.8+3412, Abdollahi et al. 2022, ApJS, 260, 53) detected by Fermi-LAT on 2025 September 20 (ATel #17407), a Swift target of opportunity observation was performed on September 22.
Swift-XRT data were taken in Photon Counting mode for a total exposure of about 2.6 ksec. The X-ray spectrum (0.3-10 keV) can be fit by an absorbed power law model with an HI column density consistent with the Galactic value in the direction of the source (n_H = 1.27 x 10^21 cm^-2, Kalberla et al. 2005, A&A, 440, 775) and a photon index of 1.49+/-0.09. The corresponding intrinsic 0.3-10 keV flux is (7.0+/-0.4) x10^-11 erg cm^-2 s^-1. This flux is significantly higher than the value observed on 2013 August 30 by Swift-XRT (ATel #5352) after the previous gamma-ray flaring activity from the source (ATel #5344). Additionally, the flux observed on 2025 September 22 is higher than all fluxes observed by Swift-XRT between 2006 and 2018 (D'Ammando 2020, MNRAS, 496, 2213).
Simultaneous Swift-UVOT observations on 2025 September 22 found 1H 0323+342 at an activity level comparable to its brightest states observed by UVOT between 2006 and 2018 (D'Ammando 2020, MNRAS 498, 859). Specifically, the observed magnitudes are V = 15.43 +/- 0.05, B = 15.88 +/- 0.05, U = 15.03 +/- 0.05, W1 = 15.21 +/- 0.06, M2 = 15.57 +/- 0.06, W2 = 15.48 +/- 0.06.
New Swift observations are planned. In consideration of the ongoing activity of this source, confirmed also by the Swift observations, we encourage further multiwavelength observations. For this source the Fermi-LAT contact person is Francesco Longo (francesco.longo@ts.infn.it).
We would like to thank the Swift Team for making these observations possible.
