Accepted Cycle 18 Theory Proposals

Proposal Number	Subject Category	PI Name	Title
18200020	STARS AND WD	Asif ud-Doula	3-D MHD models of obliquely rotating magnetic massive star winds
18200350	STARS AND WD	John Laming	The FIP to Inverse FIP Transition in Stellar Coronae
18200510	STARS AND WD	Christopher Russell	3D Hydrodynamic & Radiative Transfer Models of HETG Line Profiles from Colliding Winds
18200587	STARS AND WD	Adam Foster	Putting the Lines in the Right Places: Atomic Data for High Resolution Stellar Studies
18500546	SN, SNR AND ISOLATED NS	Sean Couch	Connecting Simulations of Violent Pre-supernovae Eruptions From Massive Stars to X-ray Observations
18700113	ACTIVE GALAXIES AND QUASARS	Eliot Quataert	Modeling the X-ray Variability of Sagittarius A* in GRMHD Simulations
18700332	ACTIVE GALAXIES AND QUASARS	Claude-Andre Faucher-Giguere	The Triggering Mechanisms and Accretion Modes of AGN: New Cosmological Simulations to Interpret Chandra Surveys
18800512	CLUSTERS OF GALAXIES	Tamara Bogdanovic	Fueling and feedback cycle of supermassive black holes in brightest cluster galaxies

Subject Category: STARS AND WD

Proposal Number: 18200020

Title: 3-D MHD models of obliquely rotating magnetic massive star winds

PI Name: Asif ud-Doula

We propose fully self-consistent 3D MHD models of obliquely rotating massive star winds. This is an extension of our earlier 2D study that examined the role of radiative cooling on x-ray emission. Our proposed general 3-D MHD simulations of magnetically confined wind shock (MCWS) models with application to specific stars with tilted-dipole or multipole fields, will facilitate the interpretation of planned and archival Chandra observations of a growing list of magnetic massive-stars and newly discovered massive magnetic binaries.

Subject Category: STARS AND WD

Proposal Number: 18200350

Title: The FIP to Inverse FIP Transition in Stellar Coronae

PI Name: John Laming

We propose to model chemical fractionation in late-type stellar coronae. The well known enhancement in abundance of elements like Fe, Mg, Si in the solar and similar stars (the FIP Effect) diminishes at later spectral types and ultimately inverts for M dwarfs (the Inverse FIP Effect). Both anomalies are captured in a model based on chromospheric ion-neutral separation by the ponderomotive force, arising as Alfven or fast mode waves propagate through or reflect from the chromosphere. Accounting for increasing mode conversion between acoustic and fast mode wave with increasing magnetic field, and using model chromospheres with the appropriate coronal irradiation, we will model this transition, and compare the resulting stellar magnetic fields with those measured directly.

Subject Category: STARS AND WD

Proposal Number: 18200510

Title: 3D Hydrodynamic & Radiative Transfer Models of HETG Line Profiles from Colliding Winds

PI Name: Christopher Russell

Chandra has invested 2.52 Ms of HETG observations into 4 colliding-wind binary (CWB) systems. WR140 and $eta$ Car are massive-star binaries with long periods that produce X-rays in a 3D, warped shock cone, while $delta$ Ori A and HD150136 are short-period systems that show line profile changes due to embedded-wind-shock emission in the primary wind being partially evacuated by the secondary wind. HETG observations resolve the velocity structure in both types of systems. We propose 3D line-profile radiative-transfer calculations on existing 3D hydrodynamic simulations of these 4 CWBs. This is the first confrontation of these data with this level of modeling, and will provide greater understanding of their stellar, wind, and orbital properties, as well as the underlying CWB shock physics.

Subject Category: STARS AND WD

Proposal Number: 18200587

Title: Putting the Lines in the Right Places: Atomic Data for High Resolution Stellar Studies

PI Name: Adam Foster

Understanding how stellar coronae are heated to several orders of magnitude hotter than the stellar photosphere remains an ongoing problem in both heliophysics and astrophysics. Several mechanisms have been proposed, but observations have not been able to comprehensively differentiate among them given existing telescopes. We propose to investigate the use of dielectronic (DR) satellite lines to explore the non-equilibrium state of the plasma, enabling us to distinguish between competing models for the coronal heating. To achieve this requires a significant effort in atomic physics to accurately resolve the DR line contributions.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 18500546

Title: Connecting Simulations of Violent Pre-supernovae Eruptions From Massive Stars to X-ray Observations

PI Name: Sean Couch

Mass loss from massive stars near the ends of their lives is not well understood. There is a great deal of evidence suggesting that this process is not dominated by steady radiative winds from the surface, but that more eruptive episodes occur also. Recently, a new subset of core-collapse supernovae have been observed that display luminous transient some days or months before the main supernova. In this project, we will model these pre-supernova eruptive transients using multidimensional simulations of unsteady nuclear burning in massive stars near to core collapse. We will model the emission from these events using an open-source radiative transfer code.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 18700113

Title: Modeling the X-ray Variability of Sagittarius A* in GRMHD Simulations

PI Name: Eliot Quataert

Sagittarius A* (Sgr A*), the supermassive black hole at the center of our galaxy, provides a unique test bed for accretion theory. Chandra observations of Sgr A* and its environment are one of the defining contributions of the Chandra mission, and have revealed variable X-ray emission produced very close to the black hole. We propose to develop detailed models of the time dependent X-ray light-curves and spectra of Sgr A* using General Relativistic MHD simulations of accretion disk-jet systems. We will compare these results to the wealth of Chandra data and identify the physical properties of the black hole and accretion flow (e.g., black hole spin, magnetic flux) required to explain the Chandra observations.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 18700332

Title: The Triggering Mechanisms and Accretion Modes of AGN: New Cosmological Simulations to Interpret Chandra Surveys

PI Name: Claude-Andre Faucher-Giguere

Chandra surveys of the extragalactic X-ray universe have played a key role in shaping our understanding of supermassive black hole (SMBH) growth but major gaps remain in our understanding of the accretion modes and triggering mechanisms of AGN activity. We will produce a suite of ultra-high resolution cosmological simulations that will follow BH accretion and feedback with unprecedented predictive power. We will predict the detailed time dependence of BH accretion, its relationship to star formation, its triggering mechanisms (mergers vs. secular), and its Eddington ratios and accretion modes as a function of redshift and galaxy properties. By comparing with available Chandra observations, we will test our state-of-the-art AGN models and enable new physical interpretation of Chandra data.

Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 18800512

Title: Fueling and feedback cycle of supermassive black holes in brightest cluster galaxies

PI Name: Tamara Bogdanovic

Several observational studies of brightest cluster galaxies (BCGs) in cool core clusters present compelling evidence that their supermassive black holes (SBHs) are capable of exerting both quasar and radio-mode feedback. Motivated by these findings we propose to use high resolution radiation magnetohydrodynamic simulations to investigate the quasar and radio-mode feedback cycle of SBHs in BCGs. The new element of this work is an in depth examination of the combined role of the two forms of feedback on physical scales where they mediate accretion onto the SBHs. This work will result in a number of predictions about the nature of SBH feedback which are directly testable in the context of Chandra observations of clusters.