Program

Presentation

The Chandra X-ray Observatory has been instrumental in establishing the X-ray properties of the Galactic population of rotation-powered ("recycled") millisecond pulsars. In this talk I will provide a summary of deep X-ray studies of globular cluster millisecond pulsars, as well as several nearby field millisecond pulsars. These include thermally-emitting recycled pulsars that may provide stringent constraints on the elusive neutron star equation of state, and so-called "redback" binary pulsars, which seem to sporadically revert to an X-ray binary-like state.

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Two fields of astrophysics have converged in the last five years: the study of accreting compact objects and the study of rotation-powered neutron stars. We can now witness the metamorphosis of a neutron star between accretion- and rotation-powered phases, in a handful of compact binary millisecond pulsars (known as "redbacks"). I will highlight Chandra's discovery of X-ray mode switching in one of the redbacks in the globular cluster M28, and discuss possible explanations for this new phenomenon. I will also present a recent systematic study of redbacks which reveals three main X-ray states (pulsar, disk and outburst states), and argue that X-ray mode switching is in fact a universal phenomenon in the disk state of redback millisecond pulsars.

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B2224+65 is well known to have a very high proper motion and to be associated with the "Guitar Nebula" in the opposite direction of the motion. A jet-like X-ray feature, however, is offset from its proper motion direction by 118 degree. Furthermore, the X-ray luminosity and morphology of the feature changed significantly between three Chandra observations. We are carrying out a detailed measurements of the X-ray spectral variation with time and across the feature and are critically testing scenarios proposed to explain this enigmatic system. The study will also have strong implications for understanding somewhat similar linear nonthermal X-ray-emitting features that have been identified in the central 100 pc region of the Galaxy.

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The high resolution capabilities provided by Chandra have provided unprecedented details about the structure of PWNe. The presence of jets, toroidal structures, shocked ejecta, and other complex structure with the nebulae provide crucial information on the conversion of spin-down energy into relativistic outflows, the spectrum of the injected particles, and the long-term evolution of these systems. Here I report on results from a series of Chandra Large Projects that have enabled detailed studies of individual PWNe to investigate their detailed structures and to provide a broad view of these systems at different stages of evolution. I concentrate, in particular, on deep observations of MSH 11-62 and G327.1-1.1, two such systems currently evolving within the confines of their host SNRs.

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The Pulsar-Wind Nebula in SNR G11.2-0.3 and its Interaction with Ejecta Abstract: The young supernova remnant (SNR) G11.2-0.3 contains a pulsar and pulsar-wind nebula (PWN) along with unusual interior thermal X-ray emission. We compare new results from a 400-ks Chandra observation with earlier Chandra and radio images to examine the PWN and its interactions with its immediate surroundings. Radio images show a clear torus perpendicular to the elongation of the X-ray PWN. The X-ray PWN is surrounded by radio structure to the NE, where it bends. We describe changes in the PWN morphology on timescales of months to years. The thermal emission may be the relic of a plane of enhanced mass loss from the progenitor. We discuss the significance of these findings for the nature of the SN that produced G11.2-0.3 and for the evolution of PWNe inside SNRs.

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The superior imaging qualities of Chandra have lead to numerous beautiful images of extended objects, many of them being supernova remnants. But these images do not just reveal the beauty of supernova remnants, but, more importantly, these observations reveal us the inner workings of supernova explosions, the dynamics of the shocks they drive into their surroundings, and they provide us with evidence that particle acceleration by supernova remnants shocks is faster than expected, and that the magnetic fields strengths around these shocks are larger than previously thought.

In this review I will focus mostly on the Chandra observations of young, historical supernova remnants. But also place the observation in the context of multiwavelength observations of these objects and modern theoretical ideas.

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The supernova of 1006 C.E. has been a valuable laboratory for probing both thermal and nonthermal X-rays and particle acceleration in fast shocks. We present results from the most detailed view of SN 1006 to date, a mosaic of 10 overlapping Chandra fields totaling 700 ks, as well as a deep optical image that reveals faint H-alpha emission around the complete 30-arcmin shell. Proper motion measurements give the shock speed around the shell, which varies from 3000 to 7400 km/s. The thin filaments along the nonthermal northeast and southwest limbs indicate strong B-field amplification, and their widths, which shrink with energy, are limited by synchrotron losses on the electrons. The sharp remnant edge we observe demands a narrow shock precursor requiring magnetic-field amplification.

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We present results from 28 ACIS observations of SN 1987A spanning the past 15 years. The soft X-ray light curve is updated and examined for evidence of a break which would indicate the forward shock has passed through the equatorial ring. The resolved Chandra images over 15 years also allow us to measure the X-ray expansion of the equatorial ring.

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Prior to Chandra, nearly all supernova remnants (SNRs) in galaxies beyond the Magellanic Clouds were discovered optically; few were detected in X-rays. But with Chandra (and XMM-Newton), large samples of X-ray detected SNRs in nearby spirals can be assembled. Some of these SNRs are ejecta-dominated, a few are remnants of historical SNe, but most are middle-aged SNRs. Here, we discuss the SNR population of the grand-design spiral M83, where we have identified at least 87 SNRs (largely along spiral arms), almost a quarter of the sources detected in 730 ks of total Chandra exposure. We use new data from HST, Gemini, and ATCA together with Chandra to study the multi-wavelength properties of the SNRs, and to compare SNRs in M83 to SNRs in our earlier Chandra study of M33.

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Chandra observations are providing critical insights into Supernova explosions and the nature of their progenitors. In this talk I will highlight some recent results from our dedicated Chandra programs that allowed us to (1) uncover the weakest engine-driven SNe and understand their link to Gamma-Ray Bursts; (2) monitor the high-energy emission from shock energy deposition into the stellar envelope as early as a few days after the onset of core-collapse; (3) put the most stringent constraints to the progenitors of Type Ia SNe by using the deepest X-ray observations ever obtained. Time Domain Astronomy is among the most promising discovery areas in the next decade. Chandra capabilities will be crucial to provide a deep X-ray view of the transient Universe.

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Type IIP (Plateau) Supernovae are the most commonly observed variety of core collapse events. They have been detected in a wide range of wavelengths from radio, through optical to X-rays. The standard picture of a type IIP supernova has the blastwave interacting with the progenitor's circumstellar matter to produce a hot region bounded by a forward and a reverse shock. This region is thought to be responsible for most of the X-ray and radio emission from these objects. Yet the origin of X-rays from these supernovae is not well understood quantitatively. The relative contributions of particle acceleration and magnetic field amplification in generating the X-ray and radio emission have been determined by recent Chandra observations and analysis of a few type IIP supernovae.

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Over the past 15 years, Chandra has obtained about 500 grating spectra of over 150 different objects in the normal stars and white dwarfs category. These cover a broad area of astrophysics, from stellar winds of hot, massive stars, magnetic activity in cool stars, accretion onto young stars, to interacting binary stars. The spectra have been key to determining fundamental stellar properties, such as abundances, densities, temperatures, and dynamics, which are all crucial to understanding the life-cycles of stars. We will look at some of the surprises, breakthroughs, and remaining puzzles, from Solar-like coronal/magnetic activity, accretion, outflows, and coronae in young stars, winds of massive OB and Wolf-Rayet stars, to outbursts of novae and cataclysmic variables.

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The shock-heated radiation-driven winds of O stars produce thermal X-ray line emission that is significantly Doppler-broadened. This makes O stars ideal for exploiting the unsurpassed spectral resolution of the Chandra gratings to study plasma kinematics and also, via their distinctive asymmetric line profile shapes, for measuring the wind absorption column densities and thus wind mass-loss rates. We present new analysis of Chandra grating spectra from a dozen O stars, showing lower mass-loss rates than predicted by theory. And by combining our X-ray derived mass-loss rates with traditional, density-squared diagnostics, we can actually use the Chandra data to also measure the wind clumping factors in these stars, which we find to be in accord with numerical simulations.

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In a 500 ks HETG observation of TW Hya, our group concluded that not only were X-rays being emitted from the accretion stream but produced a model of the detail of the structure of the accretion shock and identified hints that it was a dynamic structure. We now add to this the first simultaneous Chandra/HST(COS) spectroscopy of an accreting, young star: TW Hya. Combining our new LETGS observation with simultaneous HST FUV spectroscopy reveals temperature and density (from the X-ray spectra) as well as plasma motion (from the FUV profiles) of the accretion plasma. This allows us to step from a static accretion shock model to a fully dynamic scenario that contains the accretion funnel, the shock, and the post-shock cooling zone, and mass transfer into the transition zone and corona.

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Chandra observations elucidate the life cycle of stars and nebulae in galaxies. The Wing of the nearby SMC galaxy has very low content of metals and is an ideal laboratory to investigate an environment that closely resembles the early Universe. Our "large program" observations of star forming regions at the edge of a huge shell in the SMC Wing answered important questions about the birth, life, and death of stars. For the first time we found an accreting X-ray pulsar that is still cradled in a supernova remnant. Despite its youth the pulsar spins very slowly questioning the established theories. Using Chandra we now able to observe how stellar activity changes during stellar evolution and how stellar feedback shapes the surrounding medium in our and other galaxies.

The X-ray observing campaigns of the wind-wind colliding (WWC) binary system Eta Carinae in 2003 and 2009 presented a detailed view of the high-energy WWC activity around periastron. In the last binary orbit, Eta Carinae has shown signatures of a significant decline in the stellar mass loss, which can drastically change the X-ray activity around the latest periastron passage in this summer. We therefore launched another focused observing campaign of Eta Carinae using Chandra, XMM-Newton, Suzaku, NuSTAR and Swift, concentrating on the low X-ray flux phase around periastron, which started on July 30, 2014. We will present the early result of this observing campaign and discuss the observed spectral variation to understand the X-ray emission mechanism.

X-ray emission from massive stars is produced by shocked gas distributed throughout their unstable stellar winds. These shocks play a significant role in determining accurate stellar mass loss rates. Our current understanding of these shocks is derived from indirect indicators like line profile shapes and the f/i ratio of the He-like triplets. Here we discuss a campaign of phase-resolved Chandra grating observations and simultaneous high-precision photometry using the MOST satellite of the massive binary Delta Ori A, in an attempt to directly constrain the radial extent of the hot gas in the wind of the primary star (Delta Ori Aa) via occultation by the X-ray faint secondary (Delta Ori Ab). We present an overview of this campaign and a summary of our results.

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Chandra's spatial resolution and sensitivity are particularly well suited to the study of galaxies and the characterization of their X-ray emission. In the near universe, Chandra observations have uniquely allowed the study of X-ray source populations, both as way of understanding compact binary evolution and of probing the nature of 'extreme' sources (e.g. ULXs). With Chandra we have been able to separate cleanly the emission of discrete X-ray sources from that of the hot ISM and nuclei, leading to a fuller understanding of galaxy evolution and feedback.

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We present results from a systematic study of the X-ray binary (XRB) populations in a sample of nearby late-type galaxies from the Spitzer Infrared Nearby Galaxy Survey (SINGS). We analyze their X-ray luminosity functions (XLF) in order to measure the dependence of its shape on the average age of the stellar populations of the host galaxy. Particularly in the case of M81 by characterizing its X-ray source populations based on their optical counterparts, we disentangle and measure the XLFs of its HMXB and LMXB (field and GC) sub-populations. We also derive scaling relations between the number of X-ray binaries and the star-formation rate and stellar mass, and we compare them with results from X-ray binary population synthesis models.

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We present a 730-ks Chandra survey of the spiral galaxy M83, in conjunction with HST imaging and with new radio and optical ground-based observations. We are pursuing a broad range of science projects, highlighting Chandra's unique capability for the study of star-forming galaxies. Our most significant results so far: a) we identified different physical populations of X-ray sources, including dozens of new X-ray, radio and optical young SNRs; b) we discovered a transient ULX fed by a low-mass donor, revealing a link between ULXs and stellar-mass BHs; c) we found a microquasar with one of the most energetic jets ever found in a stellar-mass BH; d) we recovered the X-ray counterpart of SN1957D, which may now host a pulsar; e) we mapped the temperature distribution of the diffuse hot gas.

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We report on X-ray binary (XRB) populations in six nearby starburst galaxies using focused images over 0.5-30 keV with Chandra and NuSTAR. We use a set of hard X-ray color-color and color-count rate diagnostics developed using archival RXTE data, allowing identification of the much fainter extragalactic XRBs. We consistently find that the hard X-ray emission from these galaxies is dominated by XRBs (black holes and neutron stars) except in the well-known Compton-thick AGN candidate Arp 299. The detected XRBs appear dominated by intermediate-state black holes and the overall L_X is dominated by a handful of ULXs whose spectrum is overall well-described by a soft turnover. We discuss the cosmic implications of these results, including for the upcoming 7 Ms CDF-S survey.

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In the past 15 years, observations with Chandra revolutionized the study of X-ray binaries (XRBs). The unprecedented angular resolution of Chandra made possible the reliable detection of individual X-ray binaries out to ∼ 25 Mpc and the integrated emission of whole populations of XRBs out to redshift ~4. In this talk, I will overview theoretical models for the formation and evolution of XRBs in a broad range of galactic environments, and spatial and time scales; from reconstructing the evolutionary history of individual Galactic sources using detailed binary evolution calculations, to modeling the X-ray luminosity functions of extragalactic XRB populations and the redshift evolution of the global scaling relations of the emission from XRBs, using population synthesis techniques.

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Deep Chandra observations offer a view of emission from X-ray binaries (XRBs) in normal galaxies over the history of the Universe, from cosmic infancy (z~4, when the Universe was a mere 2 Gyrs old) to the “present day”. During early epochs, when metals were more rare, the formation and evolution of neutron stars and black holes differed from that at present times. As sources that probe accretion onto these objects, XRBs in distant galaxies offer clues about the influence that metallicity has on black hole formation and evolution. We also study fossils from the early Universe, which are nearby galaxies that contain less dust and have low metallicity. These objects form XRBs under conditions similar to those found in high-redshift galaxies. In this talk, I will present our studies of X-ray emission from galaxies using observations from the Chandra Deep Field-South (CDF-S) 4 Ms survey (reaching back to z=4 galaxies) along with detailed studies of relatively local (within ~100 Mpc) analogs of the distant galaxies studied in the CDF-S. These results have cosmological implications, since XRBs are expected to provide important contributions to the heating of the intergalactic medium in the early Universe and the formation of supermassive black holes.

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Recent observations with Chandra and Spitzer revealed large scale joint fluctuations in the Cosmic Infrared and Soft X-ray Backgrounds (CIB, CXB). Such a cross-power cannot be easily explained with known BH/Galaxy populations. The sources producing these coherent fluctuations show evidence of a Ly-break around ~1 m, suggesting a z>10 origin. New theoretical models suggest that this signal can be the footprint of a network of Direct Collapse Black Holes (DCBH) at z>10-12. Models postulate that early pristine gas clouds collapse into BH with mass of the order 10^5 ~ 10^6 M_solar and grow in a Compton Thick envelope of gas. In my talk I present recent results obtained with Chandra XVPs and their interpretation based on state of the art models of early BHs.

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We have selected faint AGN candidates at z>4 in the CANDELS GOODS-South field where deep multiwavelength coverage from Chandra, HST, Spitzer observations is available. High z sources are selected in the NIR H band down to very faint levels (H<27) using phot. and spectr. redshifts and then selected as AGN candidates on the basis of faint X-ray detection in the deep 4Msec Chandra image. We have estimated for the first time in the redshift interval z=4-6.5 the faint end (-21< M(1450) < -19) AGN UV luminosity function. Our candidates put a first reliable hint on the AGN photoionization rate at the epoch of reionization. What emerges from this preliminary analysis is that the faint AGNs could well be able to provide the major contribution to the reionization of the Universe at z>6.

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Chandra observations of X-ray eclipses (XRE) and Warm Absorbers (WA) in quasars produce a self-consistent view of the X-ray source and of the broad emission line region (BELR). XREs limit the size of the X-ray source and enable topographic imaging of both continuum and relativistic Fe-K. XREs imply the existence of >10(8) discrete absorbing clouds with properties consistent with being BELR clouds. These clouds are being ablated away in months and must be constantly renewed. Both eclipsing and BELR clouds have the same properties as the low ionization phase of the WAs found in LETG/HETG spectra. Hence BELR clouds must be continually condensing out of the quasar disk wind in a mist. If the clouds have not reached escape velocity they will fall toward the black hole as a quasar rain.

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Why did galaxies during their cosmological evolution stop to form stars? Why black holes in galactic nuclei have masses proportional to bulge masses? A mantra developed in the latter years suggests that AGN driven outflows may play a major role in galaxy evolution, but, is this truly the case? I will review searches for AGN feedback using X-ray, O/NIR and mm observations, and present new correlations between outflow kinetic energy, the Eddington ratio and the host galaxy SF efficiency. I will then discuss whether these observations can distinguish between two broad scenarios. In the first AGN winds regulates both further nuclear accretion and SF. In the second the correlations are interpreted as scaling laws where gas accretion and ejection and SF scale according to the galaxy size.

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Although its origin was long mysterious, the cosmic X-ray background (CXB) is now known to be primarily the sum of emission from large number of active galactic nuclei (AGN). Deep Chandra surveys have allowed us to peer deeply into the CXB and have resolved >80% of the background at 0.5--8 keV energies. I will give an overview of the composition of the CXB, and discuss the fractions of the CXB produced by Chandra sources as well as faint galaxies detected with HST. These results imply a number of still "missing" very heavily obscured AGN, which can now be probed directly with NuSTAR by studying the peak of the CXB spectrum at >10 keV. I will preview results from the NuSTAR extragalactic surveys on the contribution to the hard CXB that has been resolved by detected Chandra sources.

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One of the leading theories for the growth of supermassive black holes is that disruptive events like galaxy mergers trigger AGN by sending gas toward the black hole. During this process there should be time when AGN can be detected in both of the merging galaxies as dual or binary AGN. However, initial surveys found dual AGN are exceedingly rare, with studies based on quasars measuring only 0.1%. I will discuss current results on measuring the dual AGN fraction of nearby AGN to the smallest physical separations using the highest resolutions from Chandra. Finally, as observations become increasingly focused on measuring dual or binary AGN in galaxy mergers at the smallest separations, we are also beginning to place important constraints on recoiling black holes.

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The fallback of debris from the disruption of a star by a massive black hole can give rise to a luminous accretion-powered X-ray flare which may be visible for months to years. These tidal flares may be used to examine the accretion behavior and immediate environment of the black hole, but also to better describe the massive black hole population. We will review the important role Chandra has played in the study of tidal disruption events, particularly with respect to the study of intermediate-mass black holes and our own work on the subject. We will also discuss the importance of long-baseline X-ray studies for identifying tidal flares and for constraining models of tidal flare accretion, as Chandra moves toward 20 years and beyond.

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Chandra observations of M87 in 2004 uncovered an outburst originating in distant knot along the jet hundreds of parsecs from the core. This discovery challenges our understanding of the origin of high energy flares. Current technology is inadequate to resolve jets at distances greater than M87, or observed at higher energies. We propose to use gravitationally lensed jets to investigate the structure of more distant sources. Photons emitted at different sites cross the lens plane at different distances, thus magnification ratios and time delays differ between the mirage images. Monitoring of flares from lensed jets reveals the origin of the emission. With detectors like Chandra, lensed systems are a tool for resolving the structure of the jets and for investigating their cosmic evolution.

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We investigate the origin of non-thermal emission in relativistic astrophysical jets, with first-principles particle-in-cell (PIC) simulations. In magnetically-dominated jets, magnetic reconnection is often invoked as a mechanism to power the observed emission. With 2D and 3D PIC simulations, we show that magnetic reconnection in relativistic astrophysical jets can efficiently accelerate the particles up to extreme energies, generating a flat power-law tail with slope between -2 and -1. We discuss the dependence of the particle acceleration efficiency on the flow magnetization and composition and on the strength of the "guide field" orthogonal to the alternating fields. Our results place important constraints on the emission spectrum and morphology of relativistic astrophysical jets.

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I review some results from radiative transfer calculations for hydrodynamical simulations of mass outflows in active galactic nuclei and binary black holes. I present a few examples of how this kind of calculations have been used to test theoretical models against Chandra observations and have guided new simulations. In particular, I discuss a possibility that UV disk photons can drive a flow from a disk into a hot X-ray disk corona and couple the processes producing X-rays and UV photons. This coupling could lead to a quenching of the disk corona. I argue that this type of X-ray/UV coupling can have significant consequences on the dynamical and radiative properties in active galactic nuclei.

Actively accreting SMBHs are found, nearly universally, to create luminous X-ray emission. However, there are exceptions to this rule that provide novel insights, including PHL 1811 analogs and some weak-line quasars. We have been systematically studying such X-ray weak quasars with Chandra, and have now established the optical/UV emission-line and continuum properties that most directly trace X-ray weakness. We will report our results on the remarkable basic X-ray properties of these objects and describe their implications for models of the accretion disk/corona, emission-line formation, and quasar winds. Furthermore, we will report NuSTAR observations indicating that a significant fraction of BAL quasars are intrinsically X-ray weak, thereby promoting strong wind driving.

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The last two decades have shown us that supermassive black holes can have a profound impact on galaxies and galaxy clusters. During this talk, I will review the current status of this field, known as AGN feedback, while focussing on the most massive black holes in the Universe, those that lie at the centers of galaxy clusters. I will then review the physics behind these galaxy clusters: from shock physics, to dark matter constraints and transport processes. I will emphasize the unique role Chandra has played in the progress of these fields.

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The scaling found between mechanical and radiative power, when combined with the radio luminosity function, means that half of the radio-mode feedback in the local Universe is expected from sources within a factor of about three of the FRI/II transition. Such sources encounter a wide range of atmosphere properties. Findings from deep Chandra observations at these powers will be presented. We show that the work done in driving shocks can exceed that in evacuating cavities. We identify localized jet-gas interaction points where energy and momentum are exchanged. We present evidence of radio-emitting plasma running along boundaries between gas of different temperature, apparently lubricating the gas flows and inhibiting heat transfer, and itself being heavily structured by the process.

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We present the results of our analysis of Chandra data for FRII radio sources hosted by the BCGs: PKS B1358-113 in Abell 1836 and 4C+67.13 in Abell 578. The Chandra data augmented by VLA radio imaging, optical spectroscopy with W. Herschel Telescope, and XMM-Newton data, allowed us to investigate the nuclear activities in the targets as well as the jet/cluster gas interactions. We argue that in both sources the jets are produced with high (maximum) efficiency for given (low) accretion rates, and that the bulk of the jet kinetic power goes into the shock-heating of the ICM. We summarize our findings in the context of high-z clusters. We also re-examine various scaling relations between the jet radio power, kinetic luminosities, and accretion rate, proposed for radio sources hosted by BCGs.

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Galaxy groups provide a natural laboratory for investigating the formation of the hot intergalactic medium (IGM). While galaxy clusters gain most of their hot gas through accretion and gravitational shocks, in groups the processes of galaxy evolution (stripping, collisions, star formation) play an important role in the initial build up of the hot halo. We present Chandra and XMM-Newton observations of groups still in the process of forming their IGM, including the well known compact groups HCG 16 and Stephan's Quintet (HCG 92). We show that starburst winds and shock-heating of stripped HI provide important contributions of gas and metals to the IGM, and discuss the impact of gas stripping, enhanced star formation and nuclear activity in the group member galaxies.

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The Phoenix Cluster (SPT-CLJ2344-4243), the most X-ray luminous cluster yet discovered, is host to a massive cooling flow which appears to be fueling an extreme starburst in the central galaxy. Unlike the vast majority of clusters discovered to date, Phoenix appears to be fulfilling early cooling flow predictions, converting a substantial fraction of the cooling intracluster gas into stars (~800 Msun/yr). This runaway cooling phase appears to be short lived, and it remains unclear what triggered it and why it hasn't been observed in a larger fraction of nearby clusters. We will discuss the discovery of this system along with recent follow-up observations aimed at explaining its extreme nature, including recently-obtained deep UV and X-ray spectroscopy of the cluster core.

A Multiwavelength View of the HST Frontier Cluster MACSJ0416.1-2403 Abstract: Structure growth in the universe is one of the fundamental astrophysical problems. Merging galaxy clusters are the perfect laboratories to study the effects of structure growth on the thermal and the non-thermal particle populations in the ICM. We present results from very deep (192 ks) Chandra observations of the massive merging HST Frontier Cluster MACSJ0416.1-2403 (z=0.397, T=11 keV). We discuss evidence for shocks and turbulence in the ICM, and set constraints on the merger geometry by combining the X-ray and radio results with numerical simulations. Our analysis displays Chandra’s unmatched capability to study structure growth in the Universe, as well as the critical role of multiwavelength observations and numerical simulations.

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One of the most prominent features that the superb spatial resolution of Chandra has revealed in the galaxy cluster plasma is cold fronts: sharp surface brightness and temperature discontinuities formed by the motion of cold, dense gas. Cold fronts should be susceptible to disruption by fluid instabilites and smoothing out by thermal conduction, but many appear to be resilient to these effects, indicating suppression by microphysical processes. I will summarize a series of MHD simulations of sloshing cold fronts in galaxy clusters with anisotropic viscosity and thermal conduction. I will show that the power of cold front studies to provide constraints on the plasma conductivity is potentially strong, whereas the outlook for constraining the plasma viscosity is more uncertain.

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We present results from Chandra observations of clusters of galaxies that reveal, with exquisite detail, complex structures in the X-ray emission related to feedback from AGN in the cluster cores as well as sloshing features related to cluster-cluster interactions. We focus on two clusters: A2052 and A2029. In A2052, at least one shock driven by AGN feedback is confirmed with a measured temperature rise. A merger-induced sloshing spiral is detected with cooler temperatures and higher abundances than its surroundings. In A2029, the largest continuous sloshing spiral is revealed. The sloshing gas appears to be interacting with the central AGN's radio lobes causing them to distort. Sloshing may be an important mechanism for the creation of bent, wide-angle tail radio sources.

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X-ray observations of galaxy clusters have played an important role in cosmology over the years, and the field continues to be fruitful. I will focus on two particular observations: the gas mass fractions of dynamically relaxed clusters provide a unique measurement of the cosmic matter density and the expansion of the Universe, while surveys probing the cluster mass function are sensitive to the expansion, the initial conditions for cosmic structure formation, and the processes governing the growth of structure. I will present new work, in which previously exploited X-ray data sets are supplemented by weak gravitational lensing data, providing a precise and unbiased measurements of cluster total masses, and thereby significantly tightening cosmological constraints from clusters.

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The Planck mission provided a representative sample of galaxy clusters. From Chandra observations for the 165 Planck ESZ clusters at z < 0.35, we measure each cluster's mass, X-ray luminosity, gas mass, gas temperature, central cooling time, central entropy, the presence of active AGN and gas cavities. We will present the most interesting examples. We compare cluster properties and morphologies for X-ray and optically selected samples with the Planck ESZ sample. We find a significantly smaller fraction of cool-core clusters in the Planck sample than in X-ray selected cluster samples. However we do not find significant differences in the fraction of clusters with disturbed morphologies in the different cluster samples.

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With about 300 refereed papers published each year, XMM-Newton is one of the most successful scientific missions of ESA ever. The talk gives an overview of recent scientific highlights and achievements covering all astrophysical areas from stars, over the strong gravitational field in the vicinity of black holes, up to the most distant quasars and clusters of galaxies.

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I will discuss plans for a high-througput X-ray observatory with Chandra-like angular resolution. Building such an observatory requires new technologies for production of light-weight X-ray mirrors, as well as a new generation of science instruments. I will discuss the ongoing technology development efforts as well as the exciting science which will be made possible by such an observatory, a true successor to Chandra.

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The rapidly growing number of known young (age ~8--100 Myr) stars within ~100 pc of Earth offer unparalleled opportunities to investigate the early evolution of low-to intermediate-mass stars and the dispersal of planet-forming disks. I will present results from our ongoing XMM and Chandra studies of known and candidate members of nearby, young moving groups (NYMGs). Targeted and serendipitous X-ray observations of M-type NYMG members reveal the magnetic activity levels of very low-mass stars during their post-T Tauri evolutionary stages. Simultaneous X-ray and near-infrared spectroscopy campaigns targeting T Cha and TWA 30A, both of which are viewed through inclined, dusty accretion disks, provide insight into the compositions and clumpiness of these highly evolved disks.

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Planetary nebulae (PNe) provide textbook examples of plasma and shock processes and provide essential constraints for theories of stellar evolution and the origin and enrichment of the heavy elements in the universe. The varied shapes of PNe reveal the actions of interacting stellar winds generated by intermediate-mass stars at late stages of evolution, and evidence has been accumulating that many PNe are the products of interacting binary star systems. Hence, studies of PNe can yield insight into the progenitors of, e.g., LMXBs and SNe of Type Ia. Best known as ~10^4 K optical emission line sources, Chandra has established that a large fraction of PNe display extended X-ray emission from shock-heated plasmas of a few 10^6 K and that the central stars appear to harbor harder than expected point-like emission from sources at up to 10^7 K. I describe the discoveries, insights, and questions concerning the astrophysics of binary stars, stellar winds, and astrophysical plasmas derived from Chandra observations of PNe, with emphasis on results gleaned from the Chandra Planetary Nebulae Survey (ChanPlaNS), the first systematic X-ray survey of PNe in the solar neighborhood. I conclude with recommendations for future Chandra observations that can address open questions and maximize the insight provided by these iconic celestial objects.

Many exoplanets orbit their host stars at close distances with orbital periods of only a few days, leading to extended atmospheres and mass loss of the planet. We have detected the presence of a strongly extended exoplanetary atmosphere by achieving the first X-ray detection of an exoplanetary transit in front of its host star. Using repeated Chandra observations, we found a surprisingly deep X-ray transit with three times the optical transit depth. This can be traced back to thin outer atmosphere layers of the planet, which are transparent at optical wavelengths but opaque to X-ray photons. Such atmosphere studies are feasible for other exoplanets as well, and pilot studies in X-rays have been started. Future X-ray observatories will provide excellent opportunities to extend such studies.

Many solar system objects are now known to emit X-rays due to charge-exchange between highly charged solar wind (SW) minor ions and neutrals in their extended atmospheres, including Earth, Venus, Mars, Jupiter, and the heliosphere, with total power outputs on the MW - GW scale. (Currently only upper limits exist for Saturn and Pluto.) Chandra observations of their morphology, spectra, and time dependence provide important information about the neutral atmosphere structure and the SW flux and charge state. Chandra observations of solar x-ray scattering from Earth, Venus, Mars, Jupiter, Saturn, and the Moon have also provided important clues for the scattering material and the solar radiation field at the body. We present here a 15 year summary of Chandra's solar system observations.

We discuss observational evidence for magnetic star-planet interactions (SPI) observed in X-rays. Hot Jupiters can significantly affect the activity of their host stars through tidal and magnetic interaction, leading to both increased and decreased stellar activity levels. In the HD189733 system, not only is the star rotating faster than would be indicated by the activity of the stellar secondary, X-ray flares are found preferentially in a very restricted range of planetary phases and hint at a magnetic link between planet and star. On the other hand, WASP-18, a F6 star with a massive hot jupiter, has no signs of activity in X-rays or UV. Several age indicators (isochrone fitting, Li abundance) point to an age in 0.5-2 Gyr and thus significant activity is expected.

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The Chandra Galactic Bulge Survey (GBS) is a shallow survey with a flux limit of 1e-14 erg/cm2/s (0.5-10.0 keV) that covers a pair of 6 sq. deg. areas centred 1.5 deg. above and below the Galactic Center. The extinction and crowding in these regions are such that optical/infrared counterparts to the 1640 X-ray sources found with Chandra are accessible to detailed follow-up. The GBS is designed to set constraints on four important areas in astrophysics: stellar-mass black hole formation, the neutron star equation of state, the nature of the progenitors of type Ia supernovae and the common envelope evolution. Here I present the survey properties and goals, our multiwavelength methods to identify and clasify the counterparts to the X-ray sources and the first scientific results.

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We recently detected an unidentified emission line at 3.56 keV in the Chandra observations of the Perseus cluster and the stacked XMM-Newton observations of 73 galaxy clusters. This line was detected at >3sigma statistical significance in all three independent samples of XMM-Newton MOS and the full sample of the PN. The lack of any atomic transitions at this energy in thermal plasma, hints that the line could be a signature of decaying sterile neutrinos. I will discuss the search for this line in the stacked Suzaku observations of galaxy clusters and provide an update on active searches for this feature in other dark matter rich astrophysical systems.

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An unidentified X-ray line at ~3.55 keV has been recently claimed by several works which could possibly be attributed to a signature of dark matter particle decay or annihhilation in the halos of galaxy clusters. There has also been claimed evidence of the 3.55 keV line at the Galactic center and M31 using XMM-Newton data. We use the up-to-date Chandra observations of M31, the Galactic Center, and the Limiting Window region to search for this X-ray line. Our analysis shows no evidence for the presence of a X-ray line at 3.55 keV in any of the regions. We discuss the implication of the non-detection of the 3.55 keV line at galactic scale dark matter halo to existing dark matter models.

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It is well-known that most galaxies are missing most of their baryonic mass. Perhaps more surprisingly, they also seem to be missing most of their metals. I will present Chandra observations probing our Milky Way halo in absorption. Together with XMM and Suzaku data on emission, our results show that the Milky Way halo contains a huge reservoir of warm-hot gas that may account for a large fraction of missing baryons and metals. I'll review current status of this field, discuss implications of our results to models of galaxy formation and evolution and outline paths for future progress.

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Owing to its unprecedented ability to observe over an astounding range in flux, to image on (sub-) arcsecond angular scales, and to deliver high spectral resolution, Chandra has revolutionized (resolutionized?) our view of black hole X-ray binaries. Some of the most interesting discoveries include the detection of relativistic jets in X-rays, and accretion disk winds. Other important results have focused on the evolution of accretion flows with Eddington fraction. This talk will highlight these and other Chandra results, discuss how they have strengthened connections to massive black holes in AGN, and offer some comments on new frontiers in the Chandra + NuSTAR + Astro-H era.

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Chandra observations of globular clusters have revealed hundreds of close binaries. Correlations of their numbers with cluster mass and encounter rate have pointed at a dynamical origin for some binary types and a primoridal origin for others. I will discuss results from our Chandra observations of the oldest open clusters, which have extended these studies to the poorly-studied regime of lower densities not covered by globulars. Active binaries (ABs) and CVs in globulars are underabundant compared to old open clusters, implying that even the closest binaries in globulars are affected by binary destruction. Among open clusters the number of ABs does not scale with cluster mass, and dynamics may shape X-ray source populations at low densities, too.

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Deep Chandra observations of Circinus X-1 reveal the nebula of a young supernova remnant surrounding neutron star X-ray binary. Spectral fits indicate an age of approximately 2600 years for a source distance of 8 kpc, making Circinus X-1 the youngest known X-ray binary. The young age explains the rapid orbital evolution and the extreme swings in X-ray brightness from the accreting neutron star. The fact that Cir X-1 shows type I X-ray bursts, the lack of pulsations, and the presence of jets in this system argue for a very low magnetic field of this young neutron star, suggesting that neutron stars can be born with fields well below the canonical value of 10^12 G.

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The high sensitivity of Chandra observations have opened a window into the dynamics of HMXB production. However, significant theoretical uncertainties hamper our ability to accurately model these systems. Using a novel binary population synthesis code, we investigate the evolutionary pathways that can transform main sequence binaries into a HMXB phase. We find six classes of HMXB systems, and carefully examine the dependence of each evolutionary mode on multiple input parameters including the stellar metallicity, common envelope efficiency and natal kick distribution. We show several key results including a connection between electron-capture supernovae and the population of Be-HXMBs, and a dynamical model explaining the metallicity dependence of the ultra-luminous X-Ray binary population.

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We present observations and modeling of the SS 433 relativistic jets based on contemporaneous X-ray (from the Chandra HETGS), optical, and VLBA observations. We expand upon previous models of the jets, inferring that the X-ray emission arises less than 2 * 10^12 cm from the formation region and cools rapidly into clumps that travel ballistically beyond 10^17 cm. Modeling the X-ray spectrum shows Ni to be overabundant by * 10 and n_e can be limited to the range 10^10 - 10^13 cm^(-3) The jet Doppler shifts show a rapid change that could result from semi-relativistic shocks in interactions with local gas. We derive jet base density and temperature from the data using a radiative cooling model that includes free expansion and compute two relativistic shock scenarios.

One of the expectations with the advent of the HETG spectrometer onboard the Chandra X-ray Observatory was to measure precise photoelectric edges of major cosmic elements such as O, Ne, Mg, Si, S, Ar, Ca, and Fe. The dust content in interstellar matter and, for example, the fraction of how much oxygen is locked into dust are issues of importance and resolved X-ray edges can determine significant limits. We surveyed the Si K edge region of 10 Low-Mass X-ray Binaries and find that the K edges are from silicates in the ISM of the Bulge but there are also ionized signatures from warm plasmas local to the X-ray sources. The Si K optical depths in the Galactic Bulge show vast overabundances with respect to expected ISM abundances with columns exceeding recent predictions.

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