Accepted Cycle 10 Large and Very Large Proposals

Proposal Number: 10200509

Title: Testing the Colliding Wind Paradigm: X-rays from the Wolf-Rayet Binary System WR 147

PI Name: Svetozar Zhekov

We propose a deep HETG exposure of the Wolf-Rayet binary system WR 147. The excellent gratings and zero-order data will be used to put tight constraints on the validity of the colliding stellar wind (CSW) mechanism assumed responsible for the X-rays from this object. The detection of broad emission lines with profiles and centroids in agreement with synthetic colliding wind spectra, along with confirmation of the spatially extended X-ray emission reported from the previous short HRC-I exposure, would support the colliding wind picture. On the other hand, narrow (or unresolved) unshifted emission lines would require an interpretation other than CSW. Thus, this study will be the most rigorous test of the CSW paradigm in a WN+OB binary so far.

Proposal Number: 10400425

Title: Photospheric radius-expansion bursts at high spectral resolution

PI Name: Duncan Galloway

It has been predicted that strong (a few hundred~eV EW) photoionisation edges might be present in the X-ray spectra at the peak of photospheric radius-expansion thermonuclear bursts. We propose to search for such features in bursts from sources uniquely known to exhibit frequent radius-expansion bursts. These observations will result in detection of up to 30 thermonuclear bursts, also providing a high signal-to-noise low-flux state spectrum, as well as allowing a detailed comparison of recurrence time and energetics with numerical ignition models. Detection of discrete features from the burst spectra may lead to highly-sought constraints on the compactness and hence the neutron-star equation of state.

Proposal Number: 10400827

Title: The cooling neutron star in the super-Eddington accretor XTE J1701-462

PI Name: Jeroen Homan

Observing the cooling of neutron stars that are reheated by accretion provides new insights into neutron star structure. A detailed and efficient study of this cooling requires the use of Chandra. Here we propose to continue our ongoing monitoring campaign of the neutron star binary XTE J1701-462, a unique system that accreted at super- and near Eddington luminosities for more than 1.5 years before recently returning to quiescence. Our goal is to study the cooling of the surprisingly hot neutron star and also the evolution of the enigmatic non-thermal spectral component in unprecedented detail. Our ongoing strategy of frequent observations (every ~2.5 months) is necessary to test the most recent cooling models. We therefore request five ACIS-S observations for a total of 323 ks.

Proposal Number: 10500327

Title: An Extensive Study of the Youngest Galactic Supernova Remnant G1.9+0.3

PI Name: Stephen Reynolds

We have recently discovered that the smallest Galactic supernova remnant (SNR) in angular size, G1.9+0.3, is the youngest (known) Galactic SNR, with an age of about 100 years. The X-ray spectrum is lineless, well described by synchrotron emission with the highest rolloff frequency ever reported for a SNR. We propose a 500 ks Large Project observation of this unique object, which fills in a gap between SN 1987A (21 yr old) and Cas A (about 330). We wish to study detailed morphology, to compare with the 3 other Galactic synchrotron- dominated SNRs; spectra, to search for spatial variations and thermal emission; and variability, using this study for the first epoch. This object has enormous potential for the study of SNR hydrodynamics and strong-shock physics.

Proposal Number: 10500437

Title: The Spin and Magnetic Moment of the Neutron Star in Cassiopeia A

PI Name: Deepto Chakrabarty

How do the spin and magnetic moment of a neutron star relate to the properties of its massive progenitor and the supernova explosion? The best opportunity to study this question is the Cas A point source, the youngest known (300 yr) Galactic compact object. Its spectrum is unlike the classical Crab pulsar's, but is instead similar to both the more strongly magnetic "magnetars" and more weakly magnetic young pulsars. Much has been inferred about its progenitor and the supernova explosion from detailed studies of the supernova remnant. We propose to obtain a 500 ks HRC-S observation of the Cas A central point source, combining 350 ks of GO time and 150 ks of GTO time, in order to search for coherent pulsations down to the practical sensitivity limit of any current X-ray mission.

Proposal Number: 10500687

Title: A Deep Cycle 10 Chandra Observation of the Tycho Supernova Remnant

PI Name: John Hughes

We propose to obtain a very deep observation of the Tycho supernova remnant. Our observational goals include investigating the nature and origin of Fe-rich ejecta knots, and studying the spatial, spectral and temporal evolution of the nonthermal emission from the forward shock. Tycho is the ideal remnant for studies of cosmic-ray modified dynamics and for investigating key features of Type Ia supernova physics.

Proposal Number: 10500817

Title: The Unique Dynamical Vela Pulsar Wind Nebula

PI Name: George Pavlov

Chandra observations of the Vela pulsar-wind nebula (PWN) have revealed intriguing features in its structure and shown that the PWN brightness, shape, and spectrum change on a timescale as short as one week. Taking advantage of the known variability timescale, we propose a series of optimally sequenced observations to understand the PWN topology, dynamics, spectral structure, and interaction with the ambient matter.

Proposal Number: 10500824

Title: A Deep HETG Probe of the CSM Interaction in SN1996cr

PI Name: Franz Bauer

SN1996cr is one of the closest and X-ray brightest SNe detected on the sky. Like SN1987A, it appears to have exploded into a wind-blown bubble, sparking a unique temporal evolution wherein its X-ray flux has increased for >8 years now. Serendipitous HETG data allow us to identify several strong, broad, asymmetric emission-line complexes in SN1996cr, although their low-signal leaves much to interpretation. We propose a deep HETG observation of SN1996cr to resolve these emission lines and elucidate their nature (velocity structure, line diagnostics, abundances). It is imperative to observe SN1996cr while it remains bright, as it is the only SN beside SN1987A where such an observation is practical and in many ways is more representative of CSM-interacting core-collapse SNe.

Proposal Number: 10610785

Title: Wide, deep and sharp: A comprehensive observation of M82, the exemplar of starburst activity

PI Name: David Strickland

We propose to observe M82, the exemplar of starburst and superwind activity, with a mosaic of deep ACIS-S observations that will cover the starburst region, the galactic disk and much of the extended superwind. The region of highest resolution (FWHM < 1.5") will cover the same field of view as recent deep HST and Spitzer observations. It will be the most data-rich X-ray study of a starburst galaxy ever (>1E6 counts), and will greatly advance our knowledge of the soft X-ray-emitting gas in the superwind, the very hot metal-enriched plasma within the starburst region, and the the X-ray point source population in both the starburst region and the galactic disk. It will further complement the investment made in observing M82 by the other Great Observatories, Hubble and Spitzer.

Proposal Number: 10700504

Title: The multi-faceted X-ray activity of low-redshift active galaxies

PI Name: Mark Birkinshaw

We propose ACIS-I observations of Chandra-unobserved low-redshift 3CRR active galaxies and their environments. The data will complete Chandra observations of 3CRR at z < 0.1, making the sample useful for statistical studies. Only Chandra can resolve the multiple components of these sources, as is needed for an improved understanding of source physics and gas heating. The imaging and spectroscopy of cores, jets, hot spots, and atmospheres will be of permanent legacy value. We will use the data to investigate particle acceleration, interactions between radio plasma and the ISM and IGM, the emission mechanisms of hot spots, and AGN fueling. Comparison with our complete Spitzer coverage and HST images will aid interpretation. The dataset will be made public immediately.

Proposal Number: 10700584

Title: Deconstructing AGN X-ray Spectra - Time for a Paradigm Shift?

PI Name: Tracey Turner

We aim to detect and measure the ionization state and outflow velocities in the well-studied low-BH-mass AGN NGC 4051. We have been granted a 340 ks Suzaku observation to study continuum and low-resolution line spectral variability; HETG spectroscopy complements this by isolating narrow absorption lines arising from key zones of gas, allowing us to measure ionization, column and outflow velocities of the multiple ionized zones. A moderately ionized zone in particular can mimic the appearance of a broad Fe emission line but can be revealed by 6.5 keV Fe Kalpha absorption, for which there is already tentative evidence. A 320 ks HETG exposure will provide powerful diagnostic signatures across a wide range of ionisation. We also request HST time for tie-in UV spectroscopy.

Proposal Number: 10800641

Title: A Deep Image of the Most Powerful Cluster AGN Outburst

PI Name: Brian McNamara

Powerful AGN outbursts in galaxy clusters can release upward of 1E61 erg into the intracluster medium. Events of this magnitude are able to quench cooling flows and drive large-scale outflows that redistribute and heat the gas on cluster-wide scales. The most potent example of this is seen in the z=0.22 cluster MS0735.6+7421, whose powerful shock and cavity system have injected an estimated 6E61 erg of energy into the ICM. We propose to obtain a 500 ksec ACIS image of the cluster to examine in detail the relationships between the shock, cavity, and radio systems, and to investigate the impact of powerful AGN outbursts on the structure of the cluster.

Proposal Number: 10800762

Title: The Role of AGN in Massive Galaxy Formation

PI Name: Spencer Stanford

There is increasing evidence that high rates of star formation in massive galaxies was common in rich environments at z > 1. The leading candidate for quenching the star formation and transforming cluster galaxies into red sequence galaxies is AGN. Therefore we expect to see an increase in AGN incidence in dense environments at z > 1. We propose to systematically determine the incidence of AGN in galaxy clusters at 1 < z < 1.5 using moderately deep ACIS imaging of IR-selected clusters in the Bootes field. In conjunction with extensive data from Spitzer, HST, and Keck, we will test the AGN quenching paradigm for the origin of the stars in massive galaxies.

Proposal Number: 10800779

Title: Shocks, Ripples, and Bubbles: A Very Deep Observation of Abell 2052

PI Name: Elizabeth Blanton

The cooling flow cluster A2052 has, arguably, the morphology most similar to the Perseus cluster as seen with Chandra. Two clear bubbles to the N and S of the center of A2052 are filled with the radio lobes associated with 3C 317. Surface brightness discontinuities consistent with shocks with Mach numbers of 1.8 and 1.2 are seen near the cluster center. These may be isothermal shocks. We propose to observe Abell 2052 much more deeply to study these shock features, ripple features due to sound waves that may be found at larger radii, possible ghost bubbles, cooling gas in the bright shells around the radio source that may link the X-ray and H-alpha emission, and possible hot gas within the X-ray holes. We will directly compare the star formation and cooling rates in the cluster center.

Proposal Number: 10900836

Title: A Benchmark Observation of the Warm-Hot Intergalactic Medium

PI Name: Taotao Fang

Searching for the ``Missing baryons'', in the form of the warm-hot intergalactic medium (WHIM), is a fundamental challenge faced by the current theory of structure formation. Cosmological simulations predict that majority of the WHIM can be probed in X-ray only, yet the reported detections are often in question due to statistical and systematical issues. Based on the tentative evidence in our joint XMM-Chandra ToO observations of H 2356-309, we propose a deep, non-ToO Chandra observation to definitively detect the WHIM absorption line with a measured column density expected from theory. A null detection would place an upper limit which cannot be explained by current cosmological simulations, and put future pursuit of the WHIM with current generation of X-ray telescopes in question.