Abstract Details

Affiliation: IUCAA, Pune
Conference ID: ASI2017_547
Title : Intrinsic coronal variability in the narrow-line Seyfert 1 AGN PG1404+226
Authors and Co-Authors : Labani Mallick (IUCAA), Gulab C. Dewangan (IUCAA)
Abstract Type : Poster
Abstract Category : Extragalactic astronomy
Abstract : The X-ray emission from active galactic nuclei (AGN) is ubiquitous and shows strong persistent variability which is energy dependent. This strong variability implies that the X-ray emission is originated in the inner regions of the central engine. However, the anatomy of the AGN central engine is very complex in nature because of the presence of multiple emission components (accretion disc, corona and/or base of the relativistic jets) and the interplay between them. One of the major open questions is 'which component/mechanism is responsible for the observed energy dependent X-ray variability in AGN?'. To answer this question, we have observed one of the most promising, bright and potential AGN candidate, PG1404+226 with XMM-Newton for ∼100 ks. PG1404+226 is a narrow-line Seyfert 1 galaxy at redshift z = 0.098 and is well-known for showing large-amplitude X-ray variability on short time scales. Here we study the origin of a rapid X-ray flaring activity and quantify the variability of different spectral components (primary emission, soft excess) through time-resolved X-ray spectroscopy and frequency-averaged root mean square (rms) spectral modelling. We detected no significant UV variability (F_rms∼1%) while the soft excess varies together with the primary continuum, although with smaller amplitude. This is in agreement with the blurred reflection scenario which is further supported by the steep emissivity profile (index q∼9.5) of the accretion disc. We found very strong X-ray variability (F_rms∼84%) with an increase in overall fractional rms with energy. As such, the higher-amplitude variability becomes effective when the coronal emission exhibits enhanced variability than the soft excess. However, both the soft excess and intrinsic coronal emission are varying with large changes in the coronal flux dominating the variability. We fitted the frequency-averaged ([1.4-10]×10e-5 Hz) X-ray fractional rms spectrum of PG1404+226 in the framework of ‘two-component blurred reflection’ model in which both blurred reflection and intrinsic continuum are variable in normalization only and are perfectly coupled with each other. The fractional variations in the normalization of the intrinsic coronal and reflected disc emissions are ∼93% and ∼78%, respectively. We interpret these rapid variations in the framework of light bending model, according to which the primary coronal emission is bent down onto the accretion disc due to strong gravity and forms less variable reflection component. The nature of the rapid, energy dependent X-ray variability in PG 1404+226 prefers the ‘lamppost geometry’ of a compact corona.