Chandra X-Ray Observatory

Accepted Cycle 14 Theory Proposals

Proposal Number Subject Category PI Name Title
14200169STARS AND WDJon SundqvistX-ray Production in OB-stars: First 3-D Radiation Hydrodynamical Simulations of Embedded Wind Shocks
14200687STARS AND WDGuo-Xin ChenSolving the '3s/3d Problem' for Accurate Fe XVII Diagnostics
14300911WD BINARIES AND CVAdam FosterLine Identification and Spectral Calculations for the LETG/HRC-S
14400806BH AND NS BINARIESSusmita ChakravortyThe thermodynamics of X-ray binary winds mapped to accretion states
14500602SN, SNR AND ISOLATED NSHendrik van EertenDeveloping a hydrodynamical simulation based gamma-ray burst afterglow fit code
14610184NORMAL GALAXIES: DIFFUSE EMISSIONQ. Daniel WangSimulating Hot Gas in and around Galactic Spheroids
14700258ACTIVE GALAXIES AND QUASARSKentaro NagamineDiscriminating different AGN feedback models with multi-scale hydrodynamic simulations

Subject Category: STARS AND WD

Proposal Number: 14200169

Title: X-ray Production in OB-stars: First 3-D Radiation Hydrodynamical Simulations of Embedded Wind Shocks

PI Name: Jon Sundqvist

The strong soft X-ray emission from hot, massive stars observed with Chandra provides key information about the shock heating of these stars' dense winds. The embedded wind shocks (EWS) arise from a strong instability associated with the wind radiative driving. But present-day models of such EWS suffer from severe shortcomings (e.g. assumed spherical symmetry), limiting their direct diagnostic value. We therefore propose to develop, for the first time, full 3-D radiation hydrodynamical simulations of EWS in OB-stars. These models will be used to examine basic properties of the shock-heated gas, like temperature distributions and X-ray line widths and shapes, and thus provide crucial building blocks for follow-up investigations targeting direct comparisons to Chandra data.

Subject Category: STARS AND WD

Proposal Number: 14200687

Title: Solving the '3s/3d Problem' for Accurate Fe XVII Diagnostics

PI Name: Guo-Xin Chen

We propose to calculate the Fe XVII X-ray line emission for application to stellar and other astrophysical sources. Our calculations of 2 lines 3C at 15.01 and 3D at 15.26 Angstroms demonstrate that we can reproduce the measured line intensity ratio at lab. The calculation of the three 3s lines near 17 Angstroms is not straightforward because the effects of resonances near threshold, recombination, cascades from high-lying levels, and electron distributions can all be more important than direct excitation. The 3s/3d is a good temperature diagnostic, and may be used to test the assumption of collisional ionization equilibrium or search for non-equilibrium ionization signatures. Using the new atomic data, we will compute 3s/3d by the APEC code and disseminate the results to the community.

Subject Category: WD BINARIES AND CV

Proposal Number: 14300911

Title: Line Identification and Spectral Calculations for the LETG/HRC-S

PI Name: Adam Foster

The soft X-ray spectrum in the Chandra LETG is an important tool for observations of cool stars and classical novae, amongst other item. However, analysis of the complex spectrum in the region (60-170\AA) is made very difficult, if not impossible, by the large number of missing lines or inaccurate wavelengths in existing atomic databases. However, a large body of published line identifications from laboratory experiments exists, which would greatly enhance the spectrum here. These have not been included in current databases because they lack the complete set of atomic data to model their emission. This project will calculate the collision strengths and radiative transition rates to include these new lines in the AtomDB database, allowing the LETG spectrum to be much more fully understood.

Subject Category: BH AND NS BINARIES

Proposal Number: 14400806

Title: The thermodynamics of X-ray binary winds mapped to accretion states

PI Name: Susmita Chakravorty

We propose a systematic theory-motivated study to investigate the thermodynamic stability conditions of the disk winds in X-ray binaries (XRBs), mapped to the accretion states of the compact object. The variability of the winds is conventionally explained either by variations in the driving mechanisms or the changes in the ionizing flux. Thermodynamic instability of the wind has not been considered yet as an alternative explanation and that is what we propose to test in this project. Indeed, while this effect may not be the only one responsible for wind variability, its inclusion is crucial to understand the link between the environment of the compact object and the accretion processes.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 14500602

Title: Developing a hydrodynamical simulation based gamma-ray burst afterglow fit code

PI Name: Hendrik van Eerten

We propose a data modeling project where we perform numerical case studies based on gamma-ray burst (GRB) afterglow data from Chandra observations. We will develop a data fit code based directly on high-resolution two-dimensional relativistic hydrodynamical (RHD) simulations of GRB jets. This software will be made publicly available and we will provide support to the observational community and participate in applications. Directly fitting RHD results to data allows us to constrain important burst parameters such as explosion energy and the shape of the circumburst medium. Combined with late time Chandra data it is possible to address open questions raised by Swift observations regarding the nature of the jet break in afterglow light curves.


Proposal Number: 14610184

Title: Simulating Hot Gas in and around Galactic Spheroids

PI Name: Q. Daniel Wang

We propose a theoretical investigation of hot gas in low Lx/Lb stellar spheroids. Our existing modeling of Chandra data on such spheroids has shown that they most likely undergo subsonic outflows of hot gas, driven primarily by the feedback in form of stellar mass loss and Type Ia SNe. As such, diffuse X-ray emission from the hot gas can be used to probe the interplay between the feedback and the galactic environment. We will conduct 3-D hydrodynamic simulations of such subsonic outflows within the context of large scale galaxy formation and evolution. We will characterize the temperature, entropy, kinematic, and abundance structures of the hot gas and their effects on the measurements of the X-ray luminosity, morphology, and spectrum, which can be directly tested against the data.


Proposal Number: 14700258

Title: Discriminating different AGN feedback models with multi-scale hydrodynamic simulations

PI Name: Kentaro Nagamine

We propose to discriminate different models of AGN feedback using a series of multi-scale, high-resolution GADGET-3 SPH simulations. We employ a novel AGN feedback model developed by Ostriker et al. (2010), as well as the standard thermal feedback model adopted by others. We will compute the X-ray emissivity maps and thermal X-ray emission from our simulations, and compare to the deep Chandra imaging spectroscopy data of Seyfert galaxies by Wang et al. (2011a,b,c). Our smallest scale simulations probe gas accretion onto AGN at 0.1-200 pc; Galactic scale simulations probe 0.1-200kpc using both isolated galaxy and merging galaxies; Cosmological simulations with comoving 10-100Mpc/h box sizes will predict the evolution of AGN luminosity function and the growth of supermassive black holes.


Proposal Number: 14800826


PI Name: Elena Rasia

Recent studies on galaxy clusters have reduces by half the error on cosmological parameters. Currently, most of it has a statistical nature. With future surveys the systematic will prevail. Theoretical studies quantified differently the systematical bias in the X-ray total mass measurement: Rasia et al. (2012) found a larger bias than Nagai et al. (2007) explained by presence of temperature inhomogeneity. This proposal unifies the efforts of the two groups. By studying the temperature distribution of six sets of clusters simulated with different physics and numerical codes and by comparing our results with observational findings, we aim to identify the reason behind the disagreement in theoretical results and to evaluate how much and where simulations lack in reproducing real clusters.

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