Accepted Cycle 12 Theory Proposals

Proposal Number	Subject Category	PI Name	Title
12300716	WD BINARIES AND CV	Christopher Mauche	A Unified Model of the Soft X-ray Spectra of Dwarf Novae in Outburst
12400145	BH AND NS BINARIES	Markus Boettcher	Exploring the Disc - Jet Connection in X-Ray Binaries
12400566	BH AND NS BINARIES	Andrew Steiner	Constraining the Equation of State of Dense Matter From Isolated and Accreting Neutron Stars
12500085	SN, SNR AND ISOLATED NS	Randall Smith	Calculating the Spectra of Recombining and Charge Exchange Plasmas
12500538	SN, SNR AND ISOLATED NS	Vikram Dwarkadas	INTERPRETING THE X-RAY MORPHOLOGY OF TWO SUPERNOVA REMNANTS IN WIND-BLOWN BUBBLES OBSERVED WITH CHANDRA
12620791	NORMAL GALAXIES: X-RAY POPULATIONS	Stefan Umbreit	Formation of Black Hole X-Ray Binaries in Globular Clusters
12700437	ACTIVE GALAXIES AND QUASARS	Marta Volonteri	Hunting for double AGNs to test merger-driven activity
12700465	ACTIVE GALAXIES AND QUASARS	Daniel Proga	The role of disk winds in shaping the X-ray spectra of AGN
12800169	CLUSTERS OF GALAXIES	WILLIAM MATHEWS	The Archetypical Twin-Jet Source Cygnus A
12800826	CLUSTERS OF GALAXIES	David Rapetti	Constraining gravity with the growth of galaxy clusters

Subject Category: WD BINARIES AND CV

Proposal Number: 12300716

Title: A Unified Model of the Soft X-ray Spectra of Dwarf Novae in Outburst

PI Name: Christopher Mauche

We propose to develop a three-dimensional model of the winds of high accretion-rate cataclysmic variables --- one that accounts for their geometry and density, velocity, and ionization structure --- and adapt and apply a Monte Carlo code to accurately account for the transfer of boundary layer radiation through the wind. Using these tools, we propose to model and interpret in a uniform manner the extraordinarily disparate Chandra LETG spectra of the dwarf novae SS Cyg, U Gem, and WZ Sge in outburst, and so come to a better, more quantitative, understanding of their soft X-ray spectra and hence boundary layers and winds. Extensions of this work to related systems (e.g., AGN) should be straightforward.

Subject Category: BH AND NS BINARIES

Proposal Number: 12400145

Title: Exploring the Disc - Jet Connection in X-Ray Binaries

PI Name: Markus Boettcher

We propose a theoretical investigation to explore the disc-jet connection in black-hole X-ray binaries (BHXBs). To this end, we will enhance our existing internal-shock model for X-ray binary jets to self-consistently predict spectra and light curves due to synchrotron, synchrotron self-Compton and external Compton emission. The observables will be dictated by the properties of plasmoids in the BHXB jets which are colliding to form internal shocks. By linking the properties of those plasmoids to the rapid variability properties of the accretion disc, the spectral and variability signatures of the disc-jet connection can be explored with our proposed model development.

Subject Category: BH AND NS BINARIES

Proposal Number: 12400566

Title: Constraining the Equation of State of Dense Matter From Isolated and Accreting Neutron Stars

PI Name: Andrew Steiner

A host of observable phenomena from neutron stars can constrain the equation of state of dense matter: pulsar timing, thermal emission from cooling neutron stars, surface explosions, and gravity wave emissions are all promising areas for measurements of mass and radius. We propose to go beyond the use of X-ray bursts and determine masses and radii using results obtained from Chandra data on isolated neutron stars and quiescent low-mass X-ray binaries. Implementing a Markov Chain Monte Carlo code to analyze the the currently available statistical information, we will bridge the observations of X-ray bursts to neutron star cooling and provide details on what type of future observations and what accuracy will be required to significantly improve constraints of the equation of state.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 12500085

Title: Calculating the Spectra of Recombining and Charge Exchange Plasmas

PI Name: Randall Smith

Electronic recombination onto highly charged ions generates distinctive line and continuum emission. Recent observations of SNR such as IC443 and W49B have shown that such plasmas may be common. In addition, plasmas dominated by charge exchange (CX) emit a line-dominated spectrum that contributes to the soft X-ray background and is a major contamination source in many diffuse sources. Chandra has observed both types of plasmas, but the lack of parameterized models hinders both the identification and analysis of such sources. We propose to use the rates in the AtomDB database to calculate and publicly release two distinct spectral models: (1) a plasma undergoing collisional recombination, and (2) a plasma dominated by charge-exchange of hydrogen or helium atoms with highly charged ions.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 12500538

Title: INTERPRETING THE X-RAY MORPHOLOGY OF TWO SUPERNOVA REMNANTS IN WIND-BLOWN BUBBLES OBSERVED WITH CHANDRA

PI Name: Vikram Dwarkadas

Mass-loss from massive stars can create wind-blown "bubbles" around the star, bordered by a dense shell. Upon its death, the resulting supernova shock wave expands within the low-density bubble before impacting the shell. The impact causes it to decelerate, and a reflected shock to expand inwards. Such a scenario was suggested to explain the X-ray morphology of 2 supernova remnants (SNRs) observed with Chandra, Kes 27 and RCW 86. Herein we propose hydrodynamic models of the SNRs to test this scenario, provide a better interpretation of the X-ray morphology, and compute detailed spectra, light curves and simulated X-ray images. Our work will help to understand the general X-ray features of SNRs in wind bubbles, and enhance our knowledge of mixed-morphology remnants.

Subject Category: NORMAL GALAXIES: X-RAY POPULATIONS

Proposal Number: 12620791

Title: Formation of Black Hole X-Ray Binaries in Globular Clusters

PI Name: Stefan Umbreit

While bright Low-Mass X-ray binaries (LMXBs) are overabundant in globular clusters (GCs), LMXBs with black hole (BH) accretors (BH-LMXBs) were generally not expected to be present in GCs. However, mainly through Chandra observations, an increasing number of candidate BH-LMXBs have been found in GCs, and may form a significant fraction of the overall LMXB population in GCs. Thus, the question of the relative contribution of BH-LMXBs formed in GCs has become increasingly important for the interpretation of Chandra observations. Here we propose to model the formation of BH-LMXBs in GCs with our Monte Carlo cluster code, which allows us to determine under which conditions BH-LMXBs can be formed in sufficient numbers and to quantify their relative contribution to the total LMXB population.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 12700437

Title: Hunting for double AGNs to test merger-driven activity

PI Name: Marta Volonteri

We propose to study, by means of models of the assembly of supermassive black holes and hydrodynamical simulations, the existence and nature of double AGNs with Chandra observations. If most galaxies host black holes and galaxy mergers trigger quasar activity, then double AGNs can be used as a probe of merger-driven quasar activity. This project will provide the missing link between theoretical models of quasar triggering and observations. We will calculate: (1) the number of pairs per luminosity, redshift, (2) the merger stage when pairs light up, (3) the typical degree of obscuration of the hosts. The tools we will develop have a wide range of applicability outside the search for AGN pairs, and these results will contribute to the interpretation of archival and future observations.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 12700465

Title: The role of disk winds in shaping the X-ray spectra of AGN

PI Name: Daniel Proga

Outflows from accretion disks can impact the X-ray spectra of AGN. This possibility has fundamental implications for both our understanding of the spectra (e.g. the origin of blueshifted absorption lines and broad/red-skewed emission lines) and the manner in which AGN feedback might operate. We propose to combine the best available hydrodynamical simulations for radiatively driven AGN disk winds with state-of-the-art multi-dimensional radiative transfer simulations to make the first quantitatively reliable predictions for the X-ray spectral signatures (absorption and emission) which might be associated with such winds. Our spectra will be made available to the observer community for direct comparison with X-ray data.

Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 12800169

Title: The Archetypical Twin-Jet Source Cygnus A

PI Name: WILLIAM MATHEWS

We have developed a new gasdynamical+cosmic ray computational code that -- for the first time -- can follow the self-consistent evolution of hot cluster gas and the local energy spectrum of relativistic particles created by AGN feedback events in cluster-centered galaxies. This code allows detailed comparisons between Chandra images and non-thermal images observed at radio frequencies with comparable spatial resolution. Our new code will be tested on the spectacular classical double radio source Cygnus A where Chandra data can be used to verify many fundamental assumptions made in interpreting the radio emission.

Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 12800826

Title: Constraining gravity with the growth of galaxy clusters

PI Name: David Rapetti

Using 238 massive clusters from RASS, from which 71 and 23 have follow-up data from Chandra and ROSAT, we self-consistently constrain both cosmology and X-ray scaling relations to test gravity at cosmic scales. Our results represent the tightest, more robust constraints on the cosmic growth rate to date. We propose to extent this analysis to include the best current frameworks and specific models of modified gravity. We also plan to incorporate complementary data from the correlation of the ISW effect and matter tracers, weak lensing and galaxy surveys. To break the degeneracy between the growth rate and sigma_8, we will include weak lensing mass measurements. For this, we will improve the efficiency of the integration method to facilitate adding new model parameters into the analysis.

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