Accepted Cycle 19 Theory Proposals

Proposal Number Subject Category PI Name Title
19200517STARS AND WDGuo-Xin ChenHighly Accurate Calculation of X-ray Emission of Fe XVII
19400273BH AND NS BINARIESSophia HanEffect of exotic matter on thermal states of transiently accreting neutron stars
19400500BH AND NS BINARIESJavier GarcíaMODELING REFLECTION SPECTRA OF ULTRA-COMPACT X-RAY BINARIES
19500413SN, SNR AND ISOLATED NSHector Martinez RodriguezTesting sub-Chandrasekhar Models for Type Ia Supernovae with Chandra Observations of Supernova Remnants
19500664SN, SNR AND ISOLATED NSAndrey TimokhinTesting pair production in pulsar magnetosphere
19610542NORMAL GALAXIES: DIFFUSE EMISSIONMark VoitPrecipitation-Regulated AGN Feedback in Halos from 10^12 - 10^15 M_Sun
19700374ACTIVE GALAXIES AND QUASARSAdi FoordQuantifying Dual AGN Detectability
19700699ACTIVE GALAXIES AND QUASARSFeryal OzelUnderstanding Sgr A* with PIC Simulations of Particle Acceleration in Magnetic Reconnection
19800492CLUSTERS OF GALAXIESYuan LiThe role of magnetic fields in cool-core clusters
Subject Category: STARS AND WD

Proposal Number: 19200517

Title: Highly Accurate Calculation of X-ray Emission of Fe XVII

PI Name: Guo-Xin Chen

We propose a highly accurate calculation of the Fe XVII X-ray line emissions between 10 and 17 Angstroms for applications to stellar and astrophysical sources. Our earlier 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 proposed work is driven by the Chandra and IXPE science. The calculation is not straightforward because the effects of resonances near threshold, polarization, recombination, cascades, and electron distributions can all be more important than direct excitation. We also propose to use our new atomic data to test the assumption of collisional ionization equilibrium and search for non-equilibrium ionization signatures by the APEC code and disseminate the results to the community.

 Subject Category: BH AND NS BINARIES

Proposal Number: 19400273

Title: Effect of exotic matter on thermal states of transiently accreting neutron stars

PI Name: Sophia Han

Thermal states of neutron stars in soft X-ray transients (SXRTs) are thought to be governed by ``deep crustal heating'' in the accreted matter and cooling via emission of photons at the surface and neutrinos from the interior. Previous studies have shown that within nucleons-only model it is difficult to explain the quiescent luminosity and mean accretion rate observed for several SXRTs altogether, in particular the coldest (SAX J1808.4-3658) and the hottest (Aql X-1) neutron stars. We propose to examine the potential effects of exotic matter (i.e. hyperons, pion/kaon condensates and quark matter) on the thermal states of transiently accretion neutron stars, and provide a statistical analysis to quantify uncertainties in the constituents of matter at supranuclear densities.

 Subject Category: BH AND NS BINARIES

Proposal Number: 19400500

Title: MODELING REFLECTION SPECTRA OF ULTRA-COMPACT X-RAY BINARIES

PI Name: Javier García

The spectra of ultracompact X-ray binaries (UCXBs) show strong reflection features (including a relativistically-broadened O VIII Ly-alpha line) that can be used to constrain the radius of the neutron star primary and to understand the physics of these systems, most of which are thermonuclear burst sources. Current reflection models assume near-solar abundance, while UCXBs show hundredfold enhancements in C and O. We propose to develop reflection models tailored to UCXBs that will allow penetrating studies of archived Chandra spectra, and that will also encourage future observations of these exotic systems.

 Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 19500413

Title: Testing sub-Chandrasekhar Models for Type Ia Supernovae with Chandra Observations of Supernova Remnants

PI Name: Hector Martinez Rodriguez

While Chandrasekhar models successfully reproduce the dynamical and bulk properties of supernova remnants (SNRs), there has, of yet, been no exploration of the parameter space associated with the evolution of sub-Chandrasekhar explosion models during the SNR stage. Thus, we propose to develop the first comprehensive test of sub-Chandrasekhar scenarios into the SNR phase. Here, we will explore the evolution of these models and compare their bulk spectral and dynamical properties to the observed characteristics of Galactic and Magellanic Cloud Ia SNRs

 Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 19500664

Title: Testing pair production in pulsar magnetosphere

PI Name: Andrey Timokhin

We propose to test whether electron-positron pair creation in the outer parts of pulsar magnetosphere, strongly preferred by the most recent pulsar models, can provide enough pair plasma to account for X-ray emission of pulsar wind nebulae. We will develop a theoretical foundation for such test and apply this test to several pulsars and their nebulae observed by Chandra. The proposed method is largely independent of the details of magnetosphere models and can be used as a powerful test for a broad range of pulsar models.

 Subject Category: NORMAL GALAXIES: DIFFUSE EMISSION

Proposal Number: 19610542

Title: Precipitation-Regulated AGN Feedback in Halos from 10^12 - 10^15 M_Sun

PI Name: Mark Voit

Chandra observations of galaxy-cluster cores indicate that their AGNs regulate cooling, condensation, and star formation through precipitation-regulated feedback and raise an important question: Does precipitation-regulated AGN feedback also limit cooling and condensation of circumgalactic gas around smaller galaxies? Observations of the LX(
 Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 19700374

Title: Quantifying Dual AGN Detectability

PI Name: Adi Foord

Despite the importance of dual AGN to fields such as galaxy formation and gravitational waves, there is no quantitative method for determining whether a given X-ray observation originates from one or two AGN for sources with small (< 0.5") angular separations. Thus, there exists the possibility that we have over- or under-estimated the rate of dual AGNs. Dual AGNs with small separations can only be distinguished from point sources with advanced analysis. We will develop a Bayesian framework to quantitatively evaluate the odds ratio that a given source is single or dual. This program will allow true surveys and a significant advancement of understanding. The Bayesian framework will also be useful to a number of other fields and will be released to the community.

 Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 19700699

Title: Understanding Sgr A* with PIC Simulations of Particle Acceleration in Magnetic Reconnection

PI Name: Feryal Ozel

Sgr A* has been the subject of intense observational studies with Chandra. In the proposed work, we will investigate magnetic reconnection and particle acceleration in low-luminosity black hole accretion flows using a combination of GRMHD and particle-in-cell (PIC) simulations. We will use the PIC simulations to understand how particles are accelerated when magnetic energy is dissipated and quantify the resulting electron energy distributions. Incorporating the results of the microphysical studies into the global simulations of Sgr A*, we will investigate the origin of the intense X-ray flares observed with Chandra. We will also study how these processes affect the 1.3 mm image size in preparation for the upcoming simultaneous Chandra and EHT observations of Sgr A*.

 Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 19800492

Title: The role of magnetic fields in cool-core clusters

PI Name: Yuan Li

Chandra observations have revealed soft X-ray filaments that co-reside with H-alpha filaments in cool-core clusters. This multiphase gas likely feeds both star formation and the central AGN. Numerical simulations with AGN feedback have produced multiphase gas, but without magnetic fields, the simulated cold clouds lack the filamentary shape. Magnetic fields can also provide pressure support, inhibit mixing, and suppress star formation inside the filaments. We will perform the first high-resolution MHD simulations of realistic cool-core clusters to study how magnetic fields shape the filaments, and quantify the impact of the magnetic fields on cooling, AGN feedback, and star formation. We will produce synthetic X-ray count images and make direct comparisons to Chandra observations.