Chandra X-Ray Observatory
	(CXC)

Please note that the abstracts refer to the PROPOSED project - which is not necessarily identical to the approved project.
For accurate target information, please check the Observation Catalog.


Cycle 8 Accepted Theory Proposals

Proposal NumberSubject CategoryPI NameTitle
08200186 STARS AND WD Ming Gu Density Sensitive Line Ratios of Ne-like Ions and Effects of Resonance Excitation, Recombination and Ionization
08200747 STARS AND WD Stanley Owocki Dynamical Simulation of Magnetic Channeling and Reconnection for Hot-Star X-ray Emission
08400755 BH AND NS BINARIES Edward Brown Dim Quiescent Neutron Star Transients: Probing the EOS
08500711 SN, SNR AND ISOLATED NS Matthew Baring Electron-Proton Energy Exchange due to Electrostatic Potentials in Supernova Remnant Shocks
08610202 NORMAL GALAXIES: DIFFUSE EMISSION Shikui Tang Feedback in Galactic Bulges: Developing a Galactic Wind Model
08610968 NORMAL GALAXIES: DIFFUSE EMISSION Fabio Governato The Diffuse X-ray Emission from the Halos of Disk Galaxies: Where are the Missing baryons?
08620953 NORMAL GALAXIES: X-RAY POPULATIONS Christopher w Deloye Bright X-ray Binaries in Elliptical Galaxies: Consequences of an Ultracompact Source Nature
08700145 ACTIVE GALAXIES AND QUASARS Daniel Proga Modeling the X-ray variability of Sgr A*
08800542 CLUSTERS OF GALAXIES Christopher Reynolds Magnetohydrodynamic effects in radio-galaxy/ICM interactions
08800710 CLUSTERS OF GALAXIES Marios Chatzikos Generating A Homogeneous Library of Isolated Binary Galaxy Cluster Mergers --- Application to Dark Energy Surveys
08910496 GALACTIC DIFFUSE EMISSION AND SURVEYS Adrienne Juett A High-Resolution Model of Interstellar Absorption
08910907 GALACTIC DIFFUSE EMISSION AND SURVEYS Aigen Li X-ray Scattering and Absorption Cross Sections of Interstellar Grains: A Library and Pipeline for Modeling X-ray Halos

Subject Category: STARS AND WD

Proposal Number: 08200186

Title: Density Sensitive Line Ratios of Ne-like Ions and Effects of Resonance Excitation, Recombination and Ionization

PI Name: Ming Gu

We propose to calculate density sensitive line ratios of Ne-like ions, S VII, Ar IX, Ca XI, Fe XVII, and Ni XIX, including the effects of indirect level population mechanisms, such as resonance excitation, radiative and dielectronic recombination, and inner-shell ionization. The results will have important applications in the density determination of stellar X-ray sources.


Proposal Number: 08200747

Title: Dynamical Simulation of Magnetic Channeling and Reconnection for Hot-Star X-ray Emission

PI Name: Stanley Owocki

We propose to extend our development of dynamical models of magnetic mechanisms for hot-star X-ray emission, focusing on two parallel initiatives. The first will be to develop general 3D simulations of the Magnetically Confined Wind Shock (MCWS) model with application to stars with tilted-dipole or multipole fields. The second will be to analyze detailed plasma processes for the flare heating and X-ray emission from a newly discovered Centrifugually Driven Magnetic Reconnection (CDMR) mechanism. Both developments aim to enhance our capacity to interpret planned and archival Chandra observations of a growing list of magnetic hot-stars.


Subject Category:

Proposal Number: 08400755

Title: Dim Quiescent Neutron Star Transients: Probing the EOS

PI Name: Edward Brown

We propose to use recent observations of dim neutron star transients in quiescence to constrain the nature of matter at nuclear densities. We will construct time-dependent models of the thermally relaxing neutron star crust and use them to generate lightcurves (luminosity and effective temperatures as a function of time) for the quiescent period following an extended accretion outburst. Our calculations will survey different equations of state (EOS) and different system parameters (outburst duration, outburst accretion rate and duty cycle).These model lightcurves are essential for using archival and scheduled Chandra observations of the quiescent emission to constrain the interior temperature of the neutron star, and hence the EOS of dense matter.


Subject Category:SN, SNR AND ISOLATED NS

Proposal Number: 08500711

Title:Electron-Proton Energy Exchange due to Electrostatic Potentials in Supernova Remnant Shocks

PI Name:Matthew Baring

Electron-ion equilibration at supernova remnant shocks is a critical problem for the field, with electron temperatures inferred from Chandra X-ray line observations, and ion temperatures deduced from shock hydrodynamics or line diagnostics. The program proposed here will explore the influence of charge separation potentials on this equilibration in non-relativistic electron-ion shocks, using results from a Monte Carlo simulation. The degree of energy exchange between ions and electrons will be mapped as a function of field obliquity and shock sonic Mach number, to ascertain the electrostatic contributions to the electron heating. The simulation results will be interpreted in the light of spatially-resolved Chandra observations from prominent shell-type remnants.


Subject Category: NORMAL GALAXIES: DIFFUSE EMISSION

Proposal Number: 08610202

Title: Feedback in Galactic Bulges: Developing a Galactic Wind Model

PI Name: Shikui Tang

We request funding for a theoretical investigation of hot gas in low Lx/Lb early-type galaxies. Our preliminary study has shown that Type Ia supernova-driven galactic winds provide a natural explanation for the diffuse X-ray emission in NGC4594 and NGC4697. We will further develop and implement an 1-D wind model that can be used to fit X-ray data directly. We will conduct 3-D simulations to examine the energy conversion between the kinetic and thermal forms and to measure the density, temperature, and metallicity structures of the hot gas and their effects on X-ray morphological and spectral properties of the winds. Such an investigation is essential to understanding the energy, mass, and chemical feedback of the galactic bulges and its role in the evolution of the galaxies.


Subject Category: NORMAL GALAXIES: DIFFUSE EMISSION

Proposal Number: 08610968

Title: The Diffuse X-ray Emission from the Halos of Disk Galaxies: Where are the Missing baryons?

PI Name: Fabio Governato

Simple theoretical models greatly overestimate the observed diffuse X-ray emission from the halos of disk galaxies. We use a recently completed set of breakthrough, high resolution cosmological simulations of galaxy formation to investigate the properties of hot baryons in galaxies and the associated X-ray emission. Simulations include hydrodynamics, star formation and feedback from SN and SMBHs. We will analyze our outputs with X-MAS, a software designed to simulate observations with Chandra's ACIS. We will make predictions (as a function of z) for the expected Lx vs Vc relation for disk galaxies in a Lambda CDM Universe and will understand the role played by cooling, SN and SMBHs on the baryon budget of galaxies. Artificial observations will be made available to the community.


Subject Category: NORMAL GALAXIES: X-RAY POPULATIONS

Proposal Number: 08620953

Title: Bright X-ray Binaries in Elliptical Galaxies: Consequences of an Ultracompact Source Nature

PI Name: Christopher Deloye

The populations of bright LMXBs potentially have implications for several areas of study. Making these implications concrete requires understanding the details of the formation and evolution of these objects. Here we propose two investigations addressing the consequences of an ultracompact binary (UCB) nature for these extragalctic LMXBs. The first addresses the likely endpoints of UCB evolution with the goal of understanding what constraints the galactic millisecond pulsar population places on the source nature of elliptical LMXBs. The second considers the time evolution of the UCB formation rate in field environments and seeks to address whether UCBs provide a viable model for bright LMXBs in old field stellar populations.


Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 08700145

Title: Modeling the X-ray variability of Sgr A*

PI Name: Daniel Proga

We propose to model the X-ray flare activity of Sgr A* discovered by Chandra. Our recent time-dependent, magnetohydrodynamical simulations indicate that low angular momentum accretion flow is a promising scenario for such activity. The modeled flow is strongly variable both quantitatively (e.g., the mass- accretion rate varies with time by more than one order of magnitude) and qualitatively (e.g., the inner flow can be dominated either by an equatorial accretion torus or by a magnetized polar inflow). To test the model applicability to Sgr A*, we plan to compute radiation spectra based on the simulations. In spectra calculations, we will use Monte Carlo techniques taking into account several radiative processes. We will compare our synthetic spectra with the spectra taken by Chandra.


Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 08800542

Title: Magnetohydrodynamic effects in radio-galaxy/ICM interactions

PI Name: Christopher Reynolds

We propose 3-d magnetohydrodynamic (MHD) simulations of the interaction of a radio-galaxy with the intracluster medium (ICM) of a cooling core cluster. These will be the first such MHD simulations to follow both the jet-drive inflation and the late-time buoyant evolution of ICM cavities. We will study the injection of energy and entropy into the ICM by the AGN paying special attention to the difference between the MHD models and our existing pure-hydrodynamic models. We will also study the effects of anisotropic thermal conduction; existing work suggests that associated MHD instabilities may have important consequences for energy transport and turbulence in the ICM core. Finally, detailed X-ray maps and rotation-measure maps will be computed and compared with Chandra and VLA data.


Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 08800710

Title: Generating A Homogeneous Library of Isolated Binary Galaxy Cluster Mergers --- Application to Dark Energy Surveys

PI Name: Marios Chatzikos

Complex structures in Chandra images of galaxy cluster mergers cannot be entirely analyzed by analytical arguments, and require comparisons to numerical simulations. Yet, existing simulations in the literature are inhomogeneous in the parameter space volume they cover and the physics they include. We propose to generate a library of binary cluster mergers, with realistic physics (radiative cooling, entropy profiles, etc.), based on recent Chandra studies of relaxed clusters. We will run about 400 simulations to cover a factor of 1000 in the primary cluster mass, 10 in the subcluster mass, and 10 in the impact parameter. These simulations will also impact efforts to use clusters as a probe of cosmology and dark energy, which require accurate mass estimates for large cluster samples.


Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 08910496

Title: A High-Resolution Model of Interstellar Absorption

PI Name: Adrienne Juett

We propose to create the first interstellar absorption model that includes the high-resolution spectral structure seen in Chandra grating data. This model will be based on our previous studies of the interstellar medium (ISM) absorption edges of O, Ne, and Fe as measured in X-ray binary spectra. In addition to high-resolution structure, we will also update the model abundances and depletion values to match the observed values. We will also undertake new theoretical calculations of the absorption cross-sections for all ionization species of the higher-Z elements e.g., Mg, Si, and S. These calculations are required to advance our observational studies of ISM absorption edges in X-ray spectra.


Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 08910907

Title: X-ray Scattering and Absorption Cross Sections of Interstellar Grains: A Library and Pipeline for Modeling X-ray Halos

PI Name: Aigen Li

The X-ray halos, resulting from the small-angle scattering of X-rays by interstellar dust, probe the size, morphology, composition, and spatial distribution of dust. We propose (1) to construct the dielectric functions for various dust species from X-ray to millimeter wavelengths; (2) to calculate the X-ray scattering and absorption cross sections for various dust species of a wide range of sizes; and (3) to create a Fortran "pipeline" modeling tool for modeling the scattered X-ray halos. This program will create a web-based "library" of the dielectric functions and scattering and absorption cross sections. Both this "library" and the "pipeline" modeling tool will be made publicly available to the community on a timely fashion.


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