Name: Neeraj Kumari
Affiliation: Physical Research Laboratory Ahmedabad
Conference ID : ASI2022_389
Title : Spectral investigation of rapid variability in Narrow-Line Seyfert 1 (NLS1) galaxy NGC 4051
Authors : Neeraj Kumari, Physical Research Laboratory, Ahmedabad, India-380009 Sachindra Naik, Physical Research Laboratory, Ahmedabad, India-380009 Arghajit Jana, Institute of Astronomy, National Tsing Hua University, Hsinchu 30013, Taiwan
Abstract Type: Poster
Abstract Category : Extragalactic Astronomy
Abstract : Narrow-Line Seyfert 1 (NLS1) galaxies, a subcategory of Active Galactic Nuclei (AGNs), are known to host Super Massive Black Holes (SMBHs) and accreting matter close to the Eddington limit. In the X-ray band, the NLS1s show rapid and large variability. These objects show complex spectral features such as steep X-ray spectrum with power-law index ~2.0-2.2, signatures of cold and ionized absorption, strong soft X-ray excess below 1 keV and dip at ~7 keV. We performed a detailed spectral analysis of a NLS1 galaxy NGC 4051 in 0.3-50 keV range using simultaneous observations from XMM-Newton and NuSTAR X-ray observatories carried out in November 2018. We divided ~300 ks NuSTAR and overlapping XMM-Newton exposure into three segments, namely; pre-flare, flare and post-flare, where NuSTAR count rate was almost twice in the flaring epoch. We explored the variation of X-ray source properties in different epochs using various phenomenological and physical models. In all the epochs, we found signatures of two absorbers, one probably warm absorbers and the second similar to the Ultra-Fast Outflows (UFOs). We found a higher spectral index in the flaring epoch than the other two epochs, which shows the "softer when brighter" nature of the source. From the variability spectrum in the 0.3-10 keV range (i.e. fractional variability vs. energy), we found higher variability in low energy components such as the soft excess/ionized absorption. In this talk, I will discuss the above results and corresponding interpretations in more detail.