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 7 Accepted Theory Proposals

Proposal NumberSubject CategoryPI NameTitle
07100246SOLAR SYSTEM Vasili Kharchenko Spectra of the Charge-Exchange Mechanism for the Diffuse X-ray Background
07200173STARS AND WD Ming Gu Theoretical Wavelengths of $n\to 2$ ($3
07200879STARS AND WD Janos Zsargo Implementation of Plasma Emission Calculations into A non-LTE Radiative Transfer Program
07500095SN, SNR AND ISOLATED NS Dong Lai The Nature of Isolated, Thermally Emitting Neutron Stars
07500920SN, SNR AND ISOLATED NS George Pavlov Radiative Transitions of Once-ionized Helium in Very Strong Magnetic Fields
07620311NORMAL GALAXIES: X-RAY POPULATIONS Krzysztof Belczynski X-ray Luminosity Function Modeling for Starburst Galaxies
07620626NORMAL GALAXIES: X-RAY POPULATIONS John Fregeau Dynamical Formation of X-ray Sources in Globular Clusters
07700647ACTIVE GALAXIES AND QUASARS Timothy Kallman Combined Hydrodynamic and Spectrum Synthesis Modeling of Seyfert Torus Outflows
07700774ACTIVE GALAXIES AND QUASARS Markos Georganopoulos A toolbox for modeling images and spectra of Chandra detected Radio Galaxy jets and their hotspots.
07800390CLUSTERS OF GALAXIES Scott Randall Constraining the Self-Interaction Cross-Section of Dark Matter Using Simulations and Observations of E1 0657-56

Subject Category:SOLAR SYSTEM

Proposal Number: 07100246

Title:Spectra of the Charge-Exchange Mechanism for the Diffuse X-ray Background

PI Name: Vasili Kharchenko

We propose to construct spectra of X-ray emission induced by the Charge-Exchange (CX) collisions in the heliosphere and astrospheres. About 50% of intensity of the X-ray background below 1 keV is produced by the charge-exchange mechanism. We will investigate an influence of the CX emission on observations of cosmological objects. We will calculate X-ray and EUV emission spectra induced by the heavy solar (stellar) wind ions colliding with the neutral interstellar and geocoronal gas. CX cascading X-ray lines of highly charged Fe, Si, S, and Mg ions will be computed and together with previously calculated O, C, N, and Ne lines will be included in the synthetic CX spectra.


Subject Category:STARS AND WD

Proposal Number: 07200173

Title:Theoretical Wavelengths of $n\to 2$ ($3

PI Name: Ming Gu

We propose to calculate the wavelengths of $n\to 2$ ($3 < n < 8$) transitions in L-shell ions of iron and nickel, using a newly developed, combined configuration interaction and many-body perturbation theory approach. This method has been used to calculate the $3\to 2$ transitions of the same ions, and proven to be able to reproduce wavelengths to within a few m{\AA}. The results of this project will be used to revise astrophysical plasma emission database line list. These new wavelengths will be important for modeling stellar coronal spectra.


Subject Category:STARS AND WD

Proposal Number: 07200879

Title:Implementation of Plasma Emission Calculations into A non-LTE Radiative Transfer Program

PI Name: Janos Zsargo

We propose to combine an advanced plasma emission code (APEC) with a non-LTE stellar atmosphere code (CMFGEN) to provide model spectra for early-type stars. It will allow for combined spectral analysis of all observable wavelengths, and will simultaneously provide stellar parameters (effective temperature, abundances etc.), wind parameters (mass-loss rate, terminal velocity), and the distribution of the X-ray emitting plasma in the wind together with its temperatures and emission measures.


Subject Category:SN, SNR AND ISOLATED NS

Proposal Number: 07500095

Title:The Nature of Isolated, Thermally Emitting Neutron Stars

PI Name: Dong Lai

In the last few years, there have been significant observations (e.g. by Chandra) devoted to the study of thermal radiation from isolated neutron stars (NSs). Of particular interest are the 6-7 NSs whose spectra appear to be entirely thermal. The nature of these objects remains unclear at present, mainly because their spectra (including lines) are not yet understood. We propose to study the atmospheres and the radiation spectra of strongly magnetized NSs. We will construct atmosphere models for different compositions (H, He, C and O) and magnetic field strengths, including the effects of vacuum polarization and bound atoms. We will produce synthetic spectra and lightcurves and confront our results with observational data.


Subject Category:SN, SNR AND ISOLATED NS

Proposal Number: 07500920

Title:Radiative Transitions of Once-ionized Helium in Very Strong Magnetic Fields

PI Name: George Pavlov

Recent investigations have shown that the atmospheres of neutron stars (NSs) with very strong magnetic field are likely comprised of helium. To properly interpret the X-ray spectra from such NSs, including lines and photoionization edges, it is necessary to know the structure and radiative transitions of He ions in strong magnetic fields. We have calculated the bound states and strengths of bound-bound transitions of the He+ ion, including the nontrivial effects of the ion's motion. We propose to develop new codes, which will include the continuum and autoionizing states of He+, and calculate the radiative transitions involving such states. The results will be used for modeling helium atmospheres of NSs and interpretng the X-ray spectra of AXPs, SGRs, and radio-quiet isolated NSs.


Subject Category:NORMAL GALAXIES: X-RAY POPULATIONS

Proposal Number: 07620311

Title:X-ray Luminosity Function Modeling for Starburst Galaxies

PI Name: Krzysztof Belczynski

We propose to undertake a systematic and comprehensive study of X-ray binary populations in starburst galaxies. The modeling will be performed with the state-of-art population synthesis code StarTrack. We will calculate a set of theoretical models representative of different starburst environments. The library of XLFs for different starburst masses, ages, initial conditions and evolutionary assumptions will be constructed. The synthetic functions could then be compared against Chandra observations of nearby starburst galaxies. Matching synthetic and observed XLFs will present a new diagnostic tool for the determination of age and physical conditions within a given starburst galaxy.


Subject Category:NORMAL GALAXIES: X-RAY POPULATIONS

Proposal Number: 07620626

Title:Dynamical Formation of X-ray Sources in Globular Clusters

PI Name: John Fregeau

Bright LMXBs have been known to be overabundant in globular clusters (GCs) for 30 years, yet the details of X-ray binary formation in GCs are still not well understood. Chandra has yielded a wealth of data on low-luminosity X-ray populations (quiescent LMXBs, MSPs, active binaries, and most cataclysmic variables) in clusters, which has begun to demonstrate the importance of stellar dynamical interactions in their formation. We propose a theoretical research program combining a treatment of binary stellar evolution with GC dynamics to study the formation of X-ray sources in GCs. Comparing the predictions of our models with observations should aid in our understanding of Chandra data, and provide constraints on stellar evolutionary processes and GC initial conditions.


Subject Category:ACTIVE GALAXIES AND QUASARS

Proposal Number: 07700647

Title:Combined Hydrodynamic and Spectrum Synthesis Modeling of Seyfert Torus Outflows

PI Name: Timothy Kallman

We propose to make detailed tests of models for X-ray spectra from Seyfert 1 warm absorber outflows in which the outflow arises from ~1 pc away from the nucleus. This is likely the site of the obscuring torus implied by unification models. We plan to calculate numerical hydrodynamic models for the flow,including radiation effects and synthetic spectra in order to test this scenario for the origin of X-ray absorbing gas. A model which describes the observed spectrum will provide insight into the mass flux in the flow, the driving mechanism, and can also have implications for our understanding of Seyfert unification and the effects of the flow on the environment.


Subject Category:ACTIVE GALAXIES AND QUASARS

Proposal Number: 07700774

Title:A toolbox for modeling images and spectra of Chandra detected Radio Galaxy jets and their hotspots.

PI Name: Markos Georganopoulos

Chandra observations present us with strong arguments that the plasma flows in large scale powerful jets are substantially relativistic (Lorentz factors ~10-20) and gradually decelerating up to the hotspots, where in a collision with the intergalactic medium they become subrelativistic. We have developed the first, admittedly crude, emission models from relativistic decelerating flows that reproduce the observations of individual sources, as well as their collective behavior. Here we propose to advance these models to a more realistic physical description and make them publicly available. The models will be the only tools available to the community for mapping the jet velocity profile through fitting the broadband spectra and multiwavelenght maps of jets.


Subject Category:CLUSTERS OF GALAXIES

Proposal Number: 07800390

Title:Constraining the Self-Interaction Cross-Section of Dark Matter Using Simulations and Observations of E1 0657-56

PI Name: Scott Randall

We propose to constrain the self-interaction cross-section of dark matter, sigma, by comparing X-ray and weak-lensing observations of the galaxy cluster E1 0657-56 with results from simulations. Initial observations show that the subcluster gas core lags the dark matter clump indicating that the dark matter is not fluid-like. The unique geometry of this merger allows for three independent methods for estimating sigma. Analytic esitmates have previously been derived, but recent access to 0.5 Msec of Chandra data and a greatly improved mass map warrant a more detailed comparison with a numerical model. To this end, we propose to develop an N-body/hydrodynamical code, based on an existing code, that will be able to simultaneously handle gas dynamics and collisonal dark matter.


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Smithsonian Institute Smithsonian Institute

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 © 1998-2017. All rights reserved.