Accepted Cycle 11 Theory Proposals

Proposal Number	Subject Category	PI Name	Title
11200265	THEORY	Guo-Xin Chen	Accurate Line Ratio Diagnostics from Fe XVII
11200687	THEORY	Zhi-Yun Li	Inferring the Launching Conditions of the DG Tau X-ray Jet from Chandra Observations
11400126	THEORY	Feryal Ozel	A Comprehensive Study of the Spectra of X-ray Bursters
11400528	THEORY	Edward Brown	Charting the Neutron Star Crust with Quasi-Persistent Transients
11400552	THEORY	Tassos Fragos	A new computational tool for X-ray binary modeling: application to elliptical galaxies
11500606	THEORY	Daniel Patnaude	The Evolution of Young Supernova Remnants
11500655	THEORY	Nancy Brickhouse	The Atomic Physics of Fe K alpha: Toward Accurate Abundance Diagnostics for Supernova Remnants
11610521	THEORY	Mordecai-Mark Mac Low	Chandra Constraints on Feedback from Starburst Winds
11700190	THEORY	Tahir Yaqoob	A Comprehensive Model for Compton-thick and Compton-thin X-ray Reprocessing in AGN
11700482	THEORY	Daniel Proga	Modeling X-ray Transmission Spectra from AGN
11900445	THEORY	Renyue Cen	Better Understanding X-ray Absorbing Warm-Hot Intergalactic Medium

Subject Category: STARS AND WD

Proposal Number: 11200265

Title: Accurate Line Ratio Diagnostics from Fe XVII

PI Name: Guo-Xin Chen

We propose to produce accurate line ratios for the strongest lines of Fe XVII. Our benchmark calculations for 2 lines (3C at 15.014 and 3D at 15.262 Angstroms) demonstrate that we can reproduce their ratio as measured in the laboratory. The calculations of the three lines near 17 Angstroms are not as straightforward as for 3C and 3D because resonance effects in the cross section near threshold, direct recombination, and cascades from higher energy levels can be more important than direct excitation from the ground state. Once the atomic data are computed, we will compare the models with experimental and astrophysical data.

Subject Category: STARS AND WD

Proposal Number: 11200687

Title: Inferring the Launching Conditions of the DG Tau X-ray Jet from Chandra Observations

PI Name: Zhi-Yun Li

The recent Chandra detection of the bipolar jets of the classical T Tauri star DG Tau opens a new window on the physics of young star outflows. The X-rays most likely probe internal shocks in a highly variable, fast moving, component of the outflow that is inaccessible at other wavelengths. In this theory proposal, we seek to determine the conditions needed to launch the observed X-ray jet in the context of the widely accepted ``magnetocentrifugal'' model for outflow production. We will carry out 3D simulations of fast, variable, magnetocentrifugally driven jets from their launching surface to large, observable distances and produce synthetic X-ray images and spectra for direct comparison with Chandra observations.

Subject Category: BH AND NS BINARIES

Proposal Number: 11400126

Title: A Comprehensive Study of the Spectra of X-ray Bursters

PI Name: Feryal Ozel

We propose to calculate a complete set of X-ray spectral models for neutron stars during thermonuclear flashes that can be used in fitting high-resolution X-ray data. Our models will incorporate for the first time the complete angular redistribution of photons caused by Compton scattering and general relativistic effects in the Hartle-Thorne metric. We will generate a very large (>15K) number of models, which will allow for a detailed fitting of high resolution spectral data, and make them publicly available. This will be a major ingredient in the effort to measure the masses and radii of neutron stars using the properties of X-ray bursts.

Subject Category: BH AND NS BINARIES

Proposal Number: 11400528

Title: Charting the Neutron Star Crust with Quasi-Persistent Transients

PI Name: Edward Brown

We propose to develop a Markov Chain Monte Carlo code to fit the quiescent lightcurves of quasi-persistent transient neutron stars. Recent observations and theoretical work have shown that the cooling lightcurve is related to the core temperature, the thermal conductivity of the inner crust, and the distribution of heat sources. There are several accepted cycle 10 targets and proposed cycle 11 targets that will greatly expand our sample of observed cooling neutron star crusts. Our code, which will be made available, will facilitate in using these observations to constrain the properties of dense matter.

Subject Category: BH AND NS BINARIES

Proposal Number: 11400552

Title: A new computational tool for X-ray binary modeling: application to elliptical galaxies

PI Name: Tassos Fragos

We propose an one-year theoretical research project that focuses on: (i) The further development of an improved X-ray binary (XRB) population synthesis (PS) code that incorporates live stellar evolution, treatment of mass-transfer (MT) using a binary stellar structure and evolution code which includes full tidal treatment and MT in eccentric orbits, more realistic treatment of common envelope phases and evolution of stellar merger products. (ii) Application of this new tool towards answering the long-standing question of what is the relative contribution of the field and the globular clusters to the XRB population in the observations of early type galaxies by Chandra and what are the physical properties of these populations.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 11500606

Title: The Evolution of Young Supernova Remnants

PI Name: Daniel Patnaude

The strong shocks found in young supernova remnants heat the circumstellar medium and supernova ejecta to X-ray emitting temperatures. It is believed that these supernova remnant shocks produce the majority of Galactic cosmic rays. When acceleration is efficient, as much as 50% of the bulk kinetic energy can be lost to cosmic rays. This modifies the bulk properties of the supernova remnant, such as the shock speed, density, and temperature, properties which also impact the X-ray thermal spectrum. The proposed research will self-consistently model, for the first time, the hydrodynamics and thermal and nonthermal X-ray emission in cosmic ray modified shocks. These models will be directly compared to X-ray observations of young Galactic supernova remnants.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 11500655

Title: The Atomic Physics of Fe K alpha: Toward Accurate Abundance Diagnostics for Supernova Remnants

PI Name: Nancy Brickhouse

We propose to conduct a case study of Fe XVI K alpha emission produced during the transient ionization of a supernova remnant. This study includes critical evaluation of the existing data for electron impact inner-shell ionization and fluorescence yields, including tests conducted using a variety of theoretical atomic physics methods. Standard and newly developed atomic codes will be used. Once error estimates for the atomic data are complete, we will propagate these errors using the APEC code to simulate spectra and determine the overall accuracy of iron abundances determined from X-ray spectra.

Subject Category: NORMAL GALAXIES: DIFFUSE EMISSION

Proposal Number: 11610521

Title: Chandra Constraints on Feedback from Starburst Winds

PI Name: Mordecai-Mark Mac Low

Characterizing the mass and energy ejected by starburst winds appears required to understand the formation and evolution of galaxies and the intergalactic medium. However, interpretation of the observations using simple bubble models fails to yield reliable values because of dynamical instabilities during blowout. We propose full 3D simulations of starburst winds at resolutions sufficient to resolve individual SNe. Our goal is to produce simulated observations of winds with known energy and mass loss rates in order to calibrate Chandra observations of winds and derive the actual wind parameters of observed starbursts. This will allow us to test whether the inverse mass dependence of mass-loss efficiency favored by cosmological models is consistent with X-ray observations.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 11700190

Title: A Comprehensive Model for Compton-thick and Compton-thin X-ray Reprocessing in AGN

PI Name: Tahir Yaqoob

X-ray reprocessing is common in AGN, yet current modeling practices invoke ad hoc components, some of which may be inappropriate in the Compton-thick regime. This results in derived parameters that do not have obvious physical meaning. Our results so far indicate that the universal use of a disk geometry and interpretation of the so-called "reflection fraction" as a solid angle, can be wrong by a factor of ~5 compared to a torus geometry. We propose to compute a comprehensive set of models that improve upon previous work in several critical ways, yielding transmitted, reflected, and fluorescent line spectra that are self-consistent. The models will be suitable for many applications including Chandra grating spectroscopy and studies of AGN populations found in deep surveys, up to z~10.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 11700482

Title: Modeling X-ray Transmission Spectra from AGN

PI Name: Daniel Proga

We propose to study X-ray warm absorbers in AGN. X-ray observations, many of them obtained by Chandra, show mass outflows from AGN. We will test a very promising model for warm absorber flows, one which describes both inflows and outflows and which predicts the existence of a large volume of partially ionized gas. This work is motivated by the dramatic increase of high quality observational data and the progress made in theoretical modeling, but also by the fact there is still little contact between models and observations. We propose to change this situation. We will use our multi-dimensional simulations of the inflow/outflow model to compute X-ray spectra for various inclination angles. The key element of this proposal is to compare our synthetic spectra with Chandra data.

Subject Category: EXTRAGALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 11900445

Title: Better Understanding X-ray Absorbing Warm-Hot Intergalactic Medium

PI Name: Renyue Cen

UV observations along random lines of sight to distant quasars have revealed a significant fraction of the predicted Warm-Hot Intergalactic Medium (WHIM). This is not the case for the Chandar X-ray observation of the WHIM, although it is expected that a large fraction of the WHIM may be detected through the O VII and O VIII absorption lines in the X-rays. At present the failure of X-ray detecting the WHIM is yet not a statistically significant one due to large uncertainties in the theoretical modeling, primarily due to uncertainty in the feedback processes due to galaxy formation. Our proposed theoretical modeling aims at removing this uncertainty and provide a solid framework for the interpretation of Chandra observations and guide for future observations.

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA. Email: cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2024. All rights reserved.