AGN STORM 2. III. A NICER view of the variable X-ray obscurer in Mrk 817

Abstract

The AGN STORM 2 collaboration targeted the Seyfert 1 galaxy Mrk 817 for a year-long multiwavelength, coordinated reverberation mapping campaign including HST, Swift, XMM-Newton, NICER, and ground-based observatories. Early observations with NICER and XMM revealed an X-ray state ten times fainter than historical observations, consistent with the presence of a new dust-free, ionized obscurer. The following analysis of NICER spectra attributes variability in the observed X-ray flux to changes in both the column density of the obscurer by at least one order of magnitude ($N_{\mathrm{H}}$ ranges from $2.85\begin{array}{c}+0.48\\ -0.33\end{array}\times 10^{22}{\text{ cm}}^{-2}$ to $25.6\begin{array}{c}+3.0\\ -3.5\end{array}\times 10^{22}{\text{ cm}}^{-2}$) and the intrinsic continuum brightness (the unobscured flux ranges from $10^{-11.8}$ to $10^{-10.5}$ erg s${}^{-1}$ cm${}^{-2}$ ). While the X-ray flux generally remains in a faint state, there is one large flare during which Mrk 817 returns to its historical mean flux. The obscuring gas is still present at lower column density during the flare but it also becomes highly ionized, increasing its transparency. Correlation between the column density of the X-ray obscurer and the strength of UV broad absorption lines suggests that the X-ray and UV continua are both affected by the same obscuration, consistent with a clumpy disk wind launched from the inner broad line region.

arXiv comment19 pages, 9 figures, Accepted to ApJ

References in corpus (42)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• On the Absorption of X-rays in the Interstellar Medium
• Observational Evidence of AGN Feedback
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• An online repository of Swift/XRT light curves of GRBs
• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• On Uncertainties in Cross-Correlation Lags and the Reality of Wavelength-Dependent Continuum Lags in Active Galactic Nuclei
• Optimal binning of X-ray spectra and response matrix design
• An Explanation for the soft X-ray excess in AGN
• Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy
• X-ray reflected spectra from accretion disk models. I. Constant density atmospheres
• An Alternative Approach To Measuring Reverberation Lags in Active Galactic Nuclei
• Testing thermal reprocessing in AGN accretion discs
• An Empirical Background Model for the NICER X-ray Timing Instrument
• Reverberation mapping of Active Galactic Nuclei: from X-ray corona to dusty torus
• Observable Properties of X-ray Heated Winds in AGN: Warm Reflectors and Warm Absorbers
• The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey
• Ionized outflows from active galactic nuclei as the essential elements of feedback
• High-Density Effects in X-ray Reflection Models from Accretion Disks
• On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
• A global view of the inner accretion and ejection flow around super massive black holes: radiation driven accretion disk winds in a physical context
• Ionized outflows in local luminous AGN: what are the real densities and outflow rates?
• Magnetically-Driven Accretion-Disk Winds and Ultra-Fast Outflows in PG1211+143
• The central parsec of NGC 3783: a rotating broad emission line region, asymmetric hot dust structure, and compact coronal line region
• Direct evidence of AGN-feedback: a post starburst galaxy stripped of its gas by AGN-driven winds
• A wind-based unification model for NGC 5548: spectral holidays, non-disk emission, and implications for changing-look quasars
• The nuclear environment of the NLS1 Mrk 335: obscuration of the X-ray line emission by a variable outflow
• Space Telescope and Optical Reverberation Mapping Project. X. Understanding the Absorption-Line Holiday in NGC 5548
• Thermally driven wind as the origin of warm absorbers in AGN
• Multiphase AGN winds from X-ray irradiated disk atmospheres
• Anatomy of the AGN in NGC 5548: VII. Swift study of obscuration and broadband continuum variability
• Photoionization calculations of the radiation force due to spectral lines in AGNs
• Magnetized Disk-Winds in NGC 3783
• Dynamical thermal instability in highly supersonic outflows
• X-ray and UV Monitoring of the Seyfert 1.5 Galaxy Markarian 817
• Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817
• Time-dependent Photoionization of Gaseous Nebulae: the Pure Hydrogen Case
• The Inner Accretion Flow in the Resurgent Seyfert-1.2 AGN Mrk 817
• Thermal instability in radiation hydrodynamics: instability mechanisms, position-dependent S-curves, and attenuation curves

Cited by in corpus (4)

• AGN STORM 2. VII. A Frequency-resolved Map of the Accretion Disk in Mrk 817: Simultaneous X-ray Reverberation and UVOIR Disk Reprocessing Time Lags
• Connecting the X-ray/UV variability of Fairall 9 with NICER: A Possible Warm Corona
• A Systematic Search for X-ray Eclipse Events in Active Galactic Nuclei Observed by Swift
• Testing X-ray Reprocessing and Mapping the Soft Excess of NGC 7469 with NICER