A rapid occultation event in NGC 3227. Issue 2 (6th September 2018)

• Record Type: Journal Article
• Authors: Turner, T J; Reeves, J N; Braito, V; Lobban, A; Kraemer, S; Miller, L
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 481:Issue 2(2018)
• Page Start: 2470
• Page End: 2478
• Publication Date: 2018-09-06
• Subjects: galaxies: active -- galaxies: individual: NGC 3227 -- galaxies: Seyfert -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2447
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: NGC 3227 exhibits rapid flux and spectral variability in the X-ray band. To understand this behaviour, we conducted a coordinated observing campaign using 320 ks of XMM–Newton exposures together with 160 ks of overlapping NuSTAR observations, spanning a month. Here, we present a rapid variability event that occurs toward the end of the campaign. The spectral hardening event is accompanied by a change in the depth of an unresolved transition array (UTA), whose time-dependent behaviour is resolved using the RGS data. This UTA fingerprint allows us to identify this as a transit event, where a clump of gas having $N_\mathrm{ H} \sim 5 \times 10^{22}\, {\rm atoms\, cm^{-2}}$, log ξ ∼ 2 occults ${\sim } 60{{\ \rm per\ cent}}$ of the continuum photons over the course of approximately a day. This occulting gas is likely associated with clouds in the inner broad-line region. An additional zone of gas with lower column and higher ionization, matches the outflow velocity of the variable zone, and may represent transmission through the cloud limb.