Exploring Hard X-Ray Properties of Gamma-Ray Emitting Narrow-line Seyfert I Galaxies through NuSTAR Observations

Abstract We studied the six gamma-ray-detected Narrow Line Seyfert 1 (NLSy1) galaxies using the hard X-ray observations from Nuclear Spectroscopic Telescope Array and optical g & r band from Zwicky Transient Facility. The X-ray spectra corresponding to all objects are well-fitted with a power-law spectral model, and a strong “redder-when-brighter” (RWB) trend is seen, which is mostly seen in Blazars. The X-ray light curves were produced for all the available observations, and the F var is estimated. In 1H 0323+342, we found that F var lies between 9% and 22%, suggesting significant variability in the source. Similarly, for PKS 2004-447, we found F var lies between 10% and 21%. We see a strong X-ray and gamma-ray spectral index correlation among these objects, suggesting that these are produced through a similar process. Comparing the X-ray spectral index with other class objects, we see that NLSy1 galaxies are similar to LBL and IBL types. We see a negative trend of X-ray flux with the gamma-ray luminosity in these objects, suggesting an anticorrelation between them. A similar trend is seen between the X-ray flux, total jet power, and disk luminosity. The X-ray spectral index also shows a negative trend with total jet power and disk luminosity. The optical variability amplitude (in magnitude) lies between 0.90 and 2.32, and the fractional variability varies from 13% to 40%. The color–magnitude plot shows mostly the RWB trend, suggesting γ -NLSy1 are much closer to flat-spectrum radio quasars than BL Lacs. Our results, overall, summarize how the various parameters in gamma-ray-detected NLSy1 are connected.