Accepted Cycle 9 Archive Proposals

Proposal Number: 09100455

Title: High Resolution Imaging and Spectroscopy of the Chandra Comet Survey

PI Name: Damian Christian

We proposal to analyze the 8 comets observed with Chandra and the ACIS-S with a new atomic physics-based charge exchange emission (CXE) model. This sample of comets contains a broad variety of comets, solar wind environments and observational conditions. We will: 1) test the new CXE model spectra against the current sample of comets observed with ACIS-S; 2) investigate the temporal behavior of each comet and the spectral changes as a function of changes in the Solar Wind (such as, composition, velocity, and type) from the ACE, SOHO and STEREO; and 3) search for changes in the cometary spectra as a function of distance from the comet and search for spectral changes across the X-ray bow shock.

Proposal Number: 09100460

Title: Solar Wind Charge Exchange and the Soft X-ray Background

PI Name: Bradford Wargelin

Based on a steadily accumulating body of evidence from Chandra and other X-ray missions, it is now clear that a substantial fraction of the soft X-ray background (SXRB) arises from charge exchange (CX) between the solar wind and neutral gas surrounding the Earth and in the heliosphere. We propose to extract CX spectra from archival Chandra data with the aim of producing reliable models of geocoronal and heliospheric CX emission that can be used to predict the CX background seen in any Chandra observation, and to separate local and truly cosmic contributions to the SXRB. Our work will be aided by a recent upgrade and expansion of the ACE/SWICS solar wind monitoring database, and by selective use of contemporaneous data from XMM-Newton and Suzaku.

Proposal Number: 09200347

Title: Using Fe XVII Emission Line Ratios to Probe the X-ray Source Structure in OB Stellar Winds

PI Name: Wayne Waldron

We propose an archival research effort to demonstrate and apply the diagnostic capabilities of Fe XVII emission line ratios. Observations of these line ratios from OB stars indicate that the emission process is strongly influenced by a high density environment. Models show that the observed line ratio characteristics are produced by a combination of resonance line scattering and continuum absorption which can be sorted out by considering a collection of different Fe XVII line ratios. Hence, X-ray densities and stellar wind locations can be determined. This diagnostic will be used on all archived OB star HETGS data to study the properties of the wind distributed X-ray emission.

Proposal Number: 09300292

Title: Non-LTE Stellar Atmosphere Analyses of Super Soft X-ray Binary Sources

PI Name: Sumner Starrfield

A type Ia supernova explosion is thought to occur when a white dwarf (WD), in a close binary system, grows in mass to the Chandrasekhar Limit (CL). We have recently done calculations of accretion onto hot, massive, WDs and shown that these WDs are growing to the CL. More importantly, the surface conditions of our simulations resemble the observations of the Super Soft X-ray Binary sources (SSS) such as CAL 83 and SMC 13. The CHANDRA archives contain grating spectra of many SSS and only a few have been analyzed. We propose to use PHOENIX, our stellar atmosphere code, optimized for X-ray wavelengths, to analyze the CHANDRA spectra to better understand the connection between SSS and SN Ia.

Proposal Number: 09400683

Title: Investigating the Compact Stellar Remnant Population of the Galactic Center

PI Name: Reba Bandyopadhyay

Chandra observations of the Galactic Center have revealed a large population of discrete sources (>2000) within 20' of Sgr A*. Although their luminosity suggests that most are accretion-powered binaries, their nature cannot be determined by the Chandra data alone. Due to the high optical extinction, IR data are required for this critical enhancement of the Chandra results. We will cross-correlate 960+ ks of archival Chandra imaging with our ground-based IR data to astrometrically identify candidate counterparts. Using a detailed IR extinction map, we will derive magnitudes and colors for all the candidates. By placing photometric constraints on the nature of these sources, this project will have a dramatic impact on our knowledge of the Galactic accreting stellar remnant population.

Proposal Number: 09400741

Title: Estimating Black Hole Spin: Assessing the Importance of the Warm Absorber

PI Name: Jeffrey McClintock

In earlier work, we have estimated the spins of three stellar-mass black holes by fitting their broadband X-ray spectra to a fully relativistic model of a thin accretion disk. This archival proposal has two objectives. First, we will use this same method to obtain the first spin estimates for three additional stellar black holes: M33 X-7, XTE J1650-500, and LMC X-1, and to confirm our previous spin estimate for GRO J1655-40. Secondly, for the latter three sources we will use HETG spectra to examine any systematic effects on our spin estimates that may be caused by the warm absorbers that are known to be present in these systems. This second objective is part of our much broader effort to assess all scenarios that can ultimately call into question our estimates of black hole spin.

Proposal Number: 09400858

Title: The dirt on dust composition, size, and distribution in the Galaxy

PI Name: Julia Lee

The Chandra archive is rich with X-ray binary observations that are ideal for studying dust properties in the ISM and/or the hotter ``near binary'' environments, which has thus far remained relatively unexplored. Specifically, we will combine our on-going laboratory synchrotron work with high resolution Chandra spectra to model structure near photoelectric edges seen in XRBs that are likely attributable to ISM dust. This will be complemented with X-ray scattering halo studies to assess the size distribution of dust grains and location of grains which are tightly tied to observed halo properties. For the X-ray dippers, we will additionally be able to determine geometric distances to the source.

Proposal Number: 09500385

Title: Collisionless Shock Physics in Fully Ionized Gas

PI Name: Cara Rakowski

We propose to re-analyze the Chandra spectra from the outer-blast-wave of 3 supernova remnants propagating into fully ionized gas for which we have recently been awarded FUSE observations. Unlike previous work which focused on the ejecta, here our goal is to test a recently discovered inverse square relationship between the electron to proton temperature ratio and shock velocity, observed for shocks into partially neutral gas. Our interpretation in terms of electron heating in a cosmic-ray precursor remains sensitive to assumptions about the effect of neutrals on cosmic-ray turbulence. Shocks propagating into fully ionized gas are therefore an important test of our model.

Proposal Number: 09500704

Title: SPATIALLY-RESOLVED SPECTROSCOPY OF PULSAR-WIND NEBULAE

PI Name: Oleg Kargaltsev

We will produce accurate, adaptively binned spectral maps for a sample of seven X-ray bright pulsar-wind nebulae (PWNe) using all the ACIS data available in the archive (1.3 Ms exposure). Our goal is to provide an unbiased, robust, and convenient representations of the PWN spectral structures at 2''-20'' spatial scales. The adaptively binned spectral maps will allow us to measure the spectral differences among the compact PWN features, study cooling of shocked pulsar winds, test the results of modern PWN simulations, and facilitate further development of pulsar wind and particle acceleration models.

Proposal Number: 09620174

Title: An Archival Study of High Mass X-ray Binaries and Young Star Clusters

PI Name: Andrea Prestwich

Recent studies suggest an intriguing connection between High Mass X-ray Bianries (HMXB) and young stellar clusters: many HMXB are found close to, but not coincident with, star clusters. These observations are consistent with the suggestion that HMXBs are formed in clusters but subsequently expelled from their parent. We request archival funds to investigate the relationship between massive star clusters and HMXB formation in much more detail. Our primary goals are to determine the mechanism by which HMXBs are expelled from clusters (supernova kicks? dynamical interactions?) and investigate the effect of metallicity on HMXB production. The star clusters in our sample galaxies have well determined ages and masses from broadband UV imaging and spectroscopy.

Proposal Number: 09620596

Title: Testing for Spectral Differences between LMXBs in Metal-Rich and Metal-Poor GCs and Their Implications

PI Name: Stephen Zepf

We propose to use archival Chandra data to determine whether LMXBs in metal-poor globular clusters have different X-ray spectra than LMXBs in metal-rich clusters. We will carry out this test with archival data for four nearby elliptical galaxies. Efforts to date have come to different conclusions, possibly because of different treatment of contamination in the globular cluster samples. We will take advantage of recently available spectroscopically selected globular clusters to directly take care of any contamination and compare the X-ray spectra of LMXBs in metal-rich and metal-poor globulars. This both addresses a basic observational question and distinguishes between models for the much higher probability of a metal-rich globular cluster hosting a LMXB compared to a metal-poor one.

Proposal Number: 09700099

Title: High Resolution Spectroscopy of AGN: Maximizing the Science Return from Chandra Gratings

PI Name: Tahir Yaqoob

We propose to extend our WWW database (HotGAS) of high-level AGN grating products (http://hotgas.pha.jhu.edu) to include LETGS+ACIS data & add new HETGS data, (comprising a total of 138 observations). We will extend our study of Fe-K band diagnostics & describe here new aspects of the investigation that will be facilitated by the larger sample. The results & products database will provide a powerful resource for theorists, educators, & observers (in all wavebands), & will also be useful for planning programs & instrumentation for future missions & proposal preparation for current missions. The HotGAS products are in formats which can be easily used by non-experts & lend themselves to a wide range of scientific investigations including the study of AGN outflows & IGM absorption.

Proposal Number: 09700165

Title: On the Road to Coma: A 'Longitudinal Study' of Cluster AGN Evolution

PI Name: John Stocke

We propose an archival study of AGN in rich clusters using both X-ray and radio images to select candidates. The unique aspect of our study is the sample selection, which uses hydrodynamical N-body simulations of ICM gas evolution to select clusters that are the likely precursors to the current-day Coma Cluster. Thus, we avoid the bias inherent in flux-limited surveys where the most luminous/massive objects are studied at each epoch. The Chandra data will be analyzed to produce a uniform Tx, size, morphology and point source selection. Ground-based data will provide redshifts so that we will address cluster AGN evolution, AGN fraction, joint Xray/radio properties, cluster location, possible nuclear obscuration, and AGN contribution to cluster ICM heating.

Proposal Number: 09700236

Title: A Comprehensive Archival Search for Cluster AGN

PI Name: Paul Martini

We propose to perform a detailed archival study of ten, carefully selected, low-redshift clusters of galaxies (0.16 < z < 0.37) to address two open questions: is there a substantial increase in the AGN fraction in the outskirts of clusters? and does the AGN fraction depend on cluster properties such as redshift, mass, and dynamical state? The answer to these two questions will address the most common model for AGN fueling, other potential triggers of black hole accretion in clusters, and the feedback of cluster AGN on cluster galaxy evolution. This investigation substantially improves on previous work because all of the present archival datasets extend to the cluster virial radius and these clusters form a more representative sample of cluster properties.

Proposal Number: 09800579

Title: X-ray and Sunyaev-Zeldovich Effect scaling relations from a complete sample of clusters at 0.15PI Name: Massimiliano Bonamente

We propose to use a statistically complete sample of 35 X-ray and Sunyaev-Zeldovich Effect (SZE) clusters to study the scaling relations between the SZE flux and cluster masses. We plan to use models that take into account the complex spatial structure of the gas and its non-isothermality. The success of this effort is critical to the success of using upcoming SZE-only surveys for cosmological purposes, e.g., the South Pole Telescope survey, which will discover thousands of clusters at all redshifts. It is virtually impossible the clusters that the SPT or other SZE survey instruments will detect can be followed up individually with Chandra or other X-ray telescopes. The tool of an observationally-tested M-Y scaling relation will therefore be very valuable for cosmology at large.

Proposal Number: 09900481

Title: The Long and Short (Wavelength) of It: Radio Properties of X-ray Selected Sources in the ECDFS

PI Name: Neal Miller

We have been awarded 240 hours of Very Large Array time to produce the deepest (rms sensitivity of <= 7 uJy), highest resolution (~2") 1.4GHz radio image of the Extended Chandra Deep Field South (ECDFS) ever obtained. We are requesting Chandra Archival funding to produce a cross-matched catalog of the new radio and Spitzer data for all 900+ Chandra sources identified in the CDFS and ECDFS. This catalog will be made publicly available with our second data release, and will be instrumental in several key Chandra science objectives: 1) assessing the viability of X-ray emission as an indicator of star formation rate, 2) studying the connections between starbursts and AGN, and 3) identifying obscured AGN and evaluating their contribution to the X-ray background.

Proposal Number: 09900546

Title: Harnessing the full power of Chandra surveys

PI Name: Christine Jones

Chandra X-ray surveys are remarkably powerful tools for studying AGN and their role in cosmic evolution. Much of the most interesting science from these surveys relates to objects with X-ray fluxes that are near or below the Chandra flux limits. To harness the full power of Chandra to study these sources, we propose to use X-ray stacking analyses in three public multiwavelength surveys that span the full range of Chandra area and depth: the Chandra Deep Fields, the Extended Groth Strip, and the 9 deg^2 Bootes survey. Using STACKFAST, a new and powerful X-ray stacking code, we will study (1) highly obscured AGN, (2) the nature of extremely faint X-ray sources, (3) the role of environment in AGN activity, and (4) the nature of accretion in radio-loud AGN.