Publications (28)
AGN STORM 2. IV. Swift X-ray and ultraviolet/optical monitoring of Mrk 817
Edward M. Cackett, Jonathan Gelbord, Aaron J. Barth +48
The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emissio…
Synthetic absorption lines for a clumpy medium: a spectral signature for cloud acceleration in AGN?
Tim Waters, Daniel Proga, Randall Dannen +1
There is increasing evidence that the highly ionized multiphase components of AGN disk winds may be due to thermal instability. The ions responsible for forming the observed X-ray…
The AGN broad line region as a clumpy turbulent outflow: a physical basis for LOC modeling
Tim Waters, Hui Li
Many studies have considered the roles of clouds, outflows, and turbulence in producing the broad emission and absorption lines in the spectra of active galactic nuclei (AGNs). How…
Clumpy AGN outflows due to thermal instability
Randall Dannen, Daniel Proga, Tim Waters +1
One of the main mechanisms that could drive mass outflows on parsec scales in AGN is thermal driving. The same X-rays that ionize and heat the plasma are also expected to make it t…
Irradiation of Astrophysical Objects - SED and Flux Effects on Thermally Driven Winds
Sergei Dyda, Randall Dannen, Tim Waters +1
We develop a general method for the self consistent calculation of the hydrodynamics of an astrophysical object irradiated by a radiation field with an arbitrary strength and spect…
Dynamical thermal instability in highly supersonic outflows
Tim Waters, Daniel Proga, Randall Dannen +1
Acceleration can change the ionization of X-ray irradiated gas to the point that the gas becomes thermally unstable. Cloud formation, the expected outcome of thermal instability (T…
AGN STORM 2: II. Ultraviolet Observations of Mrk817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope
Y. Homayouni, Gisella De Rosa, Rachel Plesha +62
We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk817 using 165 spectra obtained with the Cosmic Or…
On Synthetic Absorption Line Profiles of Thermally Driven Winds from Active Galactic Nuclei
Shalini Ganguly, Daniel Proga, Tim Waters +7
The warm absorbers observed in more than half of all nearby active galactic nuclei (AGN) are tracers of ionized outflows located at parsec scale distances from the central engine.…
Reverberation Mapping of the Broad Line Region: application to a hydrodynamical line-driven disk wind solution
Tim Waters, Amit Kashi, Daniel Proga +3
The latest analysis efforts in reverberation mapping are beginning to allow reconstruction of echo images (or velocity-delay maps) that encode information about the structure and k…
Multiphase AGN winds from X-ray irradiated disk atmospheres
Tim Waters, Daniel Proga, Randall Dannen
The mechanism of thermal driving for launching mass outflows is interconnected with classical thermal instability (TI). In a recent paper, we demonstrated that as a result of this…
Magnetothermal disk winds in X-ray binaries: poloidal magnetic fields suppress thermal winds
Tim Waters, Daniel Proga
Magnetic, radiation pressure, and thermal driving are the three mechanisms capable of launching accretion disk winds. In X-ray binaries, radiation pressure is often not significant…
AGN STORM 2. III. A NICER view of the variable X-ray obscurer in Mrk 817
Ethan R. Partington, Edward M. Cackett, Erin Kara +44
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, NI…
Catastrophic cooling instability in optically thin plasmas
Tim Waters, Amanda Stricklan
The solar corona is the prototypical example of a low density environment heated to high temperatures by external sources. The plasma cools radiatively, and because it is optically…
Cloud Formation and Acceleration in a Radiative Environment
Daniel Proga, Tim Waters
In a radiatively heated and cooled medium, the thermal instability is a plausible mechanism for forming clouds, while the radiation force provides a natural acceleration, especiall…
The saturation mechanism of thermal instability
Tim Waters, Daniel Proga
The literature on thermal instability (TI) reveals that even for a simple homogeneous plasma, the nonlinear outcome ranges from a gentle reconfiguration of the initial state to an…
On the stability analysis of astrophysical cooling functions
Amanda Stricklan, Tim Waters, James Klimchuk
To model the temperature evolution of optically thin astrophysical environments at MHD scales, radiative and collisional cooling rates are typically either pre-tabulated or fit int…
Thermal instability in radiation hydrodynamics: instability mechanisms, position-dependent S-curves, and attenuation curves
Daniel Proga, Tim Waters, Sergei Dyda +1
Local thermal instability can plausibly explain the formation of multiphase gas in many different astrophysical environments, but the theory is only well understood in the opticall…
Cloud coalescence: a dynamical instability affecting multiphase environments
Tim Waters, Daniel Proga
The mass and size distributions are the key characteristics of any astrophysical objects, including the densest clumps comprising the cold phase of multiphase environments. In our…
AGN STORM 2: I. First results: A Change in the Weather of Mrk 817
Erin Kara, Missagh Mehdipour, Gerard A. Kriss +69
We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for it…
On the transition from efficient to inefficient line-driving in irradiated flows
Randall Dannen, Daniel Proga, Tim Waters
Observations of ionized AGN outflows have provided compelling evidence that the radiation field transfers both momentum and energy to the plasma. At parsec scale distances in AGN,…
Non-isobaric Thermal Instability
Tim Waters, Daniel Proga
Multiphase media have very complex structure and evolution. Accurate numerical simulations are necessary to make advances in our understanding of this rich physics. Because simulat…
Position dependent radiation fields near accretion disks
Kara Smith, Daniel Proga, Randall Dannen +2
In disk wind models for active galactic nuclei (AGN) outflows, high-energy radiation poses a significant problem wherein the gas can become overionized, effectively disabling what…
AGN STORM 2: V. Anomalous Behavior of the CIV Light Curve in Mrk 817
Y. Homayouni, Gerard A. Kriss, Gisella De Rosa +49
An intensive reverberation mapping campaign on the Seyfert 1 galaxy Mrk817 using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) revealed significant vari…
Photoionization calculations of the radiation force due to spectral lines in AGNs
Randall C. Dannen, Daniel Proga, Timothy R. Kallman +1
One of the main mechanisms that could drive mass outflows in AGNs is radiation pressure due to spectral lines. Although straightforward to understand, the actual magnitude of the r…
On the efficient acceleration of clouds in active galactic nuclei
Tim Waters, Daniel Proga
In the broad line region of AGN, acceleration occurs naturally when a cloud condenses out of the hot confining medium due to the increase in line opacity as the cloud cools. Howeve…
Outflows from inflows: the nature of Bondi-like accretion
Tim Waters, Aycin Aykutalp, Daniel Proga +3
The classic Bondi solution remains a common starting point both for studying black hole growth across cosmic time in cosmological simulations and for smaller scale simulations of A…
Parker Winds Revisited: An Extension to Disk Winds
Tim Waters, Daniel Proga
A simple, one-dimensional dynamical model of thermally driven disk winds, one in the spirit of the original Parker (1958) model, is presented. We consider two different axi-symmetr…
AGN STORM 2: IX. Studying the Dynamics of the Ionized Obscurer in Mrk 817 with High-resolution X-ray Spectroscopy
Fatima Zaidouni, Erin Kara, Peter Kosec +45
We present the results of the XMM-Newton and NuSTAR observations taken as part of the ongoing, intensive multi-wavelength monitoring program of the Seyfert 1 galaxy Mrk 817 by the…