26-30 June 2023
Centro Congressi Federico II
Europe/Rome timezone

Searching for X-ray eclipses in NGC 6814 using dense optical/UV to X-ray monitoring with Swift

26 Jun 2023, 15:15
Aula Magna (Centro Congressi Federico II)

Aula Magna

Centro Congressi Federico II

Via Partenope, 36, Napoli, Italy


Dr. Adam Gonzalez (Saint Mary's University)


NGC 6814 is a nearby ($z = 0.005$) Seyfert 1.5 galaxy that we recently showed had undergone a rapid X-ray occultation event during an XMM-Newton observation from 2016. The X-ray eclipse of high column ($N_{\mathrm{H}} \approx 10^{23}~\mathrm{cm}^{-2}$), mildly ionised ($\log\xi \approx 1~\mathrm{erg~cm~s^{-1}}$) matter lasted ~45ks, with ingress and egress each lasting ~14ks, revealing a partially covered X-ray region we estimated to be ~25 gravitational radii across. From August to November 2022 we observed NGC 6814 3-4 times per day with Swift to search for new X-ray eclipses to better understand the environment in this AGN. We present here a new analysis of the 2016 XMM-Newton data using X-ray colour-colour diagrams that reveal an inhomogeneous, clumpy obscurer, which is likely embedded within an extended, large scale structure based on simultaneous and long-term Swift coverage. Our 2022 Swift campaign reveals no new X-ray eclipses, but offers a rich data set with which we conduct the first thermal reverberation analysis of this AGN. We find highly correlated optical/UV to X-ray variability that exhibits a significantly flatter time-lag spectrum than the predicted 4/3 power law relation of a standard X-ray illuminated accretion disc. Furthermore, we find that during the 2016 X-ray eclipse X-rays de-correlate from optical/UV variation before resuming highly correlated broad band variability ~30 days later.

Primary authors

Dr. Adam Gonzalez (Saint Mary's University) Mr. Ben Pottie (Saint Mary's University) Prof. Luigi Gallo (Saint Mary's University) Prof. Jon Miller (University of Michigan) Dr. Elias Kammoun (Institut de Recherche en Astrophysique et Planétologie (IRAP))

Presentation Materials

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