Abstracts of Talks

Click on the talk title to view abstract and co-Author information.

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  • Steve Allen
  • (Stanford University)
  • Chandra and Cluster Cosmology
  • Chandra observations of galaxy clusters have played an important role inhelping to consolidate the standard model of cosmology, with a universedominated by dark matter and dark energy. Early Chandra measurements ofthe baryonic mass fraction in clusters enabled precise constraints to beplaced on the mean matter density of the Universe, while the extensionof these measurements to higher redshifts enabled the first directconfirmation of the discovery from supernovae studies that the expansionof our Universe is accelerating. Chandra observations transformedcosmological studies with cluster counts, enabling the first detectionof the effects of dark energy in slowing the growth of cosmic structure.Throughout it's twenty year mission, Chandra has provided key insightsinto the nature of dark matter, facilitating stringent tests of the colddark matter paradigm. It has also enabled novel tests of fundamentalphysics, spanning gravity, neutrino properties and inflation.
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  • Vallia Antoniou
  • (Texas Tech University and Center for Astrophysics | Harvard & Smithsonian)
  • Chandra's 20-year view of X-ray binaries in the Milky Way and nearby galaxies
  • Chandra has revolutionized our view of X-ray binary populations. Its superbangular and spectral resolution has allowed us to observe these systems inan unprecedented way in a variety of galactic environments. Studies ofX-ray binaries in the Milky Way and nearby galaxies have enabled us toaddress where and how they are formed, what are the evolutionary end-pointsof their progenitors, and what fraction undergoes an X-ray luminous phase.Scaling nearby populations in terms of system mass and local star-formationrate has also allowed us to use them as proxies for more distant galaxieswhere X-ray populations cannot be resolved. In this talk, I will review theglobal X-ray properties of the X-ray binary populations of nearby galaxiesrevealed by 20 years of Chandra discoveries. I will discuss questions raisedby both X-ray binary population studies and studies of individual objectsof interest, and prospects for yet further progress from futureobservations.
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  • Andrea Belfiore
  • (inaf-iasf mi)
  • Diffuse emission around an ultra-luminous X-ray pulsar
  • Ultraluminous X-ray sources (ULXs) are extragalactic X-ray emitters located off-center of their host galaxy and with a luminosity in excess of a few 1039 L, if emitted isotropically. The discovery of periodic modulation revealed that in some ULXs the accreting compact object is a neutron star (NS), indicating luminosities substantially above their Eddington limit. The most extreme object in this respect is NGC 5907 ULX-1 (ULX1), with a peak luminosity that exceeds by 500 times its Eddington limit. During a Chandra observation to probe a low state of ULX1, we detected diffuse X-ray emission at the position of ULX1. Its diameter is 2.7±1.0 arcsec and contains 25 photons, none below 0.8 keV. We interpret this extended structure as an expanding nebula powered by the wind of ULX1. Its diameter of about 200 pc, characteristic energy of ∼1.9 keV, and luminosity of ∼2×1038 L imply a mechanical power of 1.3×1041 L and an age ∼7×104 yr. This interpretation suggests that a genuinely super-Eddington regime can be sustained for time scales much longer than the spin-up time of the NS powering the system. Since the mechanical power from a single ULX nebula can rival the injection rate of cosmic rays of an entire galaxy, ULX nebulae could be important cosmic ray accelerators.
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  • Breanna Binder
  • (Cal Poly Pomona)
  • Revisiting the Lx-SFR Relationship in Nearby Galaxies
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  • Valentina Braito
  • (UMBC)
  • Chandra high resolution map of the emitting regions of NGC 7582
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  • Becky Canning
  • (Stanford University / KIPAC)
  • AGN Evolution in the Universe's Densest Environments
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  • Urmila Chadayammuri
  • (Yale University)
  • Constraining plasma microphysics with MHD simulations and Chandra X-ray Visionary Program Observations of the merging cluster Abell 2146
  • Cluster mergers are rich astrophysical laboratories, allowing us to constrain otherwise extremely elusive properties such as the strength of viscosity, thermal conduction and collisional processes in the intra-cluster medium. Abell 2146 is a Bullet Cluster-like merging system, whose slightly lower mass, and thus, temperature, place it at the peak sensitivity of Chandra. We present simulations designed to match properties of this system seen in the 2Ms legacy-class observation.These ultradeep observations reveal several key structures that allow us to anchor our simulations - a leading or bow shock, a strong cold front, a cold spur-like plume, and an upstream shock. The relative positions, brightness and temperature of these features jointly constrain the merger geometry and dynamics, as described by the impact parameter, relative velocity, halo masses and concentrations, coolness of the initial cores, and orientation of the merger axis with respect to the plane of the sky. As a first step, we constrained these parameters with a suite of non-radiative hydrodynamical simulations, automating the process of identifying and quantifying sharp, extended features. Once the merger geometry is determined, we run a second suite, sequentially adding magnetic fields, viscosity (both isotropic and Braginskii) and thermal conduction. The electron-ion thermal equilibration timescale affects the widths of shock fronts, the ICM viscosity sets the scale of the turbulent eddies shredding the subcluster core, and the conduction rate affects the temperature of cool gas blobs breaking off the cool core. We present preliminary constraints on the plasma parameters, along with associated degeneracies, and make the (comparison) code publicly available for future analyses of merging cluster systems.
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  • Koushik Chatterjee
  • (University of Amsterdam)
  • The First High-Resolution GRMHD studies of accretion in Sgr A*
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  • Francesca Civano
  • (Center for Astrophysics | Harvard & Smithsonian)
  • In medio stat virtus: the Chandra COSMOS Legacy Survey
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  • Stéphane Corbel
  • (Univ. Paris & Obs. Paris & CEA Saclay)
  • Chandra reveals multiple X-ray jets in black hole X-ray binaries
  • During periods of outburst activity, black hole X-ray binaries are known to produce bright radio flares during state transitions. This is a signature of synchrotron emission from relativistic electrons ejected from the system with large bulk velocities. In a few cases, such jets have been imaged at radio wavelengths into one-(or two-)sided components moving away from the black hole, sometimes with apparent velocities greater than the speed of light (similar to AGNs).

    Thanks to the exquisite spatial resolution of Chandra, we discovered relativistic jets in X-rays in XTE J1550-564 and H1743-322. In this talk, we will present new detections of X-ray jets in additional sources (GX 339-4, MAXI J1820+070 and possibly others ), describe the jets' deceleration and morphology evolution, and highlight the extreme particle re-acceleration that occurs when the relativistic jets interact with the interstellar medium. Based on the observed behavior, such phenomena appear more common than previously thought and we will discuss the overall implications.

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  • Lia Corrales
  • (University of Michigan)
  • The low-luminosity accretion flow of Sgr A* as seen by Chandra HETG
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  • Edmund Douglass
  • (Farmingdale State College - SUNY)
  • Off-Axis Mergers and Cool Core Disruption in Galaxy Clusters
  • Spiral-shaped regions of enhanced X-ray surface brightness are found in some of the most relaxed galaxy clusters in the Universe (e.g. A2029). The formation of such spirals is attributed to the sloshing of a dense cool core (CC) about the bottom of the cluster's gravitational potential well. The process, initiated by an off-axis encounter with a subcluster, is generally found to leave the CC fairly intact. However, the recent identification of cluster-wide spirals in systems lacking strong-CCs (A1763, A2142) suggests that more violent off-axis mergers may be capable of inducing core sloshing to the point of CC destruction. To further investigate this phenomenon we have analyzed a sample of systems with intermediate-to-high core entropy ( K0>30 keV cm2) which do not appear to be undergoing major head-on mergers. We find numerous systems displaying spiral excesses with ICM cores in various states of disruption, challenging the notion that low angular momentum mergers are required for non-cool core (NCC) formation. Such findings expand our understanding of the dynamical conditions capable of CC destruction and suggest that off-axis mergers play a greater role in establishing the NCC cluster population than previously assumed.
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  • William Dunn
  • (UCL - Mullard Space Science Laboratory, CfA | Harvard & Smithsonian)
  • A New Revolution for Planetary X-ray Emission Through Chandra and Juno
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  • Vikram Dwarkadas
  • (University of Chicago)
  • X-ray Spectroscopy of Young Supernovae with Chandra
  • Chandra's arc-second spatial resolution, combined with its spectral sensitivity, make it an excellent instrument to study young supernovae (SNe), months to years after outburst. We illustrate this with particular focus on SN 1996cr, a nearby Type IIn SN with a peculiar X-ray and radio lightcurve that was increasing with time for several years, indicative of interaction with a dense shell. Numerical hydrodynamic simulations, combined with synthetic spectral calculations and comparison to observations, enable us to excavate the SN environment, trace the evolution of the shock wave within the circumstellar medium (CSM), and hone in on the SN progenitor. A 480 ks HETG observation in 2009, coupled with HETG exposures in 2000 and 2004, and other lower signal-to-noise exposures, allow us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines, explore possible geometrical models to describe the line profile, provide new insighhts into the SN morphology, and monitor the line evolution as a tracer of the ejecta-CSM interaction. We show that a polar geometry with two distinct opening angle configurations and internal obscuration can successfully reproduce all of the observed line profiles.
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  • Pepi Fabbiano
  • (Center for Astrophysics | Harvard & Smithsonian)
  • The Einstein Observatory
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  • Chiara Feruglio
  • (INAF OATs)
  • Chandra, ALMA and MUSE@VLT reveal feeding & feedback in obscured AGN
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  • Francesca Fornasini
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Connecting the metallicity dependence and redshift evolution of HMXBs
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  • Kristen Garofali
  • (University of Arkansas)
  • On the Nature of the 0.3–30 keV Spectrum of Low-Metallicity Starburst Galaxy VV114 Based on Chandra, XMM, and NuSTAR
  • Binary population synthesis combined with cosmological models suggest that X-ray binaries (XRBs) could be an important, and perhaps dominant, source of heating for the intergalactic medium prior to the epoch of reionization. The power of such models for predicting the importance of XRBs in the early universe relies on empirical constraints on XRB X-ray spectral energy distributions (SEDs); however, such empirical constraints are currently lacking for XRB populations in low-metallicity galaxies, where the environments probed more closely resemble that of the early universe. Using a combination of Chandra, XMM-Newton, and NuSTAR observations we present new constraints on the 0.3-30 keV SED of the low-metallicity, starburst galaxy VV114, which is known to host an excess of ultra-luminous X-ray sources above 1040 erg/s. Critically, only Chandra is capable of resolving the emission into individual point sources in VV114. We use archival Chandra observations to constrain the contributions to the SED from the X-ray point sources, including a likely active galactic nucleus (AGN) in the eastern region of VV114, and the XRB population. We extend the spectral model derived from the Chandra data to newly acquired, near-simultaneous XMM-Newton and NuSTAR observations of VV114 to measure the contribution of the XRB population to the galaxy spectrum at energies > 10 keV. Using our best-fit spectral model, we derive the XRB SED of VV114 which we compare to similar studies of XRB SEDs in higher-metallicity galaxies. Finally, we discuss the implications of the measured shape of the low-metallicity XRB SED in VV114 for the importance of the emission from XRB populations in the high redshift universe during the cosmic epoch of heating.
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  • Konstantin Getman
  • (Pennsylvania State University)
  • Insights into Young Star Cluster Astrophysics Based on Chandra Observations
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  • Hans Moritz Günther
  • (MIT)
  • New tricks for a mature observatory: Chandra HETG/HRC-I observations of TW Hya probe the structure of accretion
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  • Daryl Haggard
  • (McGill University)
  • Chandra's Legacy of Discovery in Transient Astrophysics
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  • Paul Hertz
  • (NASA)
  • X-ray Astronomy and the Future of Astrophysics
  • Access to the X-ray sky is a critical capability for understanding the universe and advancing NASA’s strategic goals in astrophysics. This was recognized by the 1980 Decadal Survey when the Chandra X-ray Observatory was designated the highest priority for a large space mission. For the past twenty years, astronomers confirmed the value of X-ray observations by applying Chandra data to every problem in astrophysics, from supermassive black holes to the habitability of exoplanets. Chandra remains one of NASA’s Great Observatories, a key component of a portfolio of NASA missions that provide multi-wavelength observations of the cosmos. This talk will provide a NASA-centric view of the current status and future plans for astrophysics, including the key role that Chandra and its successor X-ray observatories play.
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  • Ryan Hickox
  • (Dartmouth College)
  • Science with deep surveys: Evolution of black holes and galaxies and the cosmic X-ray background
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  • David Huenemoerder
  • (MIT)
  • A Deep Exposure in High Resolution X-Rays Reveals the Hottest Plasma in the zeta Puppis Wind
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  • Xiangyu Jin
  • (McGill University)
  • Connecting Changing-Look Quasar's Optical/X-ray Spectral Shapes and Accretion Rates
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  • Mackenzie Jones
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Large Scale Extended Hard X-ray Emission in NGC 7212 with Chandra
  • Recent observations of nearby Compton Thick (CT) active galactic nuclei (AGN) with Chandra have resolved hard X-ray emission extending out from the central supermassive black hole (SMBH) to kpc scales, challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines originate in the inner ∼pc due to the excitation of obscuring material. Here I will present the results of the most recent Chandra ACIS-S observations of NGC 7212, a CT AGN in a compact group of interacting galaxies. We find that ∼19% of the emission associated with hard X-ray continuum and Fe K line is extended both along the ionization cone and in the cross-cone direction on kpc scales. The spectra of NGC 7212 is best represented by a mixture of thermal and photoionization models, consistent with what is observed for other CT AGN (e.g., ESO 428-G014), indicating the presence of complex gas interactions. These observations, when coupled with what we know from other extended sources, will provide a foundation for understanding how AGN feedback impacts host galaxies on galactic scales.
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  • Christine Jones
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Uhuru - Probing the "hoary deep" in a New Light with the First Orbiting X-ray Observatory.
  • Uhuru, led by PI Riccardo Giacconi and launched on December 12, 1970, wasthe first orbiting X-ray observatory. Designed and built by scientists atAmerican Science and Engineering - AS&E - in Cambridge, MA, Uhuru rotatedslowly, with its proportional counters scanning a great circle on the skyroughly every 12 minutes. A fraction of each day's observations werepromptly sent to AS&E and quickly analyzed, so changes could be rapidlymade to the observing program to follow-up new discoveries. The firstresults from Uhuru were submitted to ApJ Letters only two months afterlaunch. Compared with the generally large positional uncertainties fromrocket detections of X-ray sources, the accurate locations of Uhurusources enabled identification of optical and radio counterparts for bothGalactic and extragalactic sources. Important discoveries from Uhuruincluded detection of periodic pulsations from X-ray binaries on timescalesof seconds (Hercules X-1 and Centaurus X-3), with a precision sufficient tostudy their orbital periods; discovery of short time scale variability fromCygnus X-1, confirming the existence of black holes; detection of X-rayemission from extragalactic AGN (3C273 and Cen A); identification of galaxyclusters as extended X-ray sources; and determination of the log N - log Sof extragalactic X-ray sources, which argued that the X-ray backgroundarose from discrete sources.
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  • Jelle Kaastra
  • (SRON)
  • A new era of AGN outflow studies initiated by Chandra's LETGS
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  • Margarita Karovska
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Chandra's Sub-arcsecond Resolution View of Wind Accreting Interacting Symbiotic Binaries
  • Chandra's sub-arcsecond angular resolution at X-ray wavelengths offers unprecedented opportunities for detailed studies of accretion phenomena in many astronomical sources, ranging from YSOs to AGNs. These include interacting binaries, where the signatures of accretion processes are very prominent. Among the interacting binaries, Symbiotic systems (a compact source e.g., a white dwarf accreting from a mass losing red giant) are of a particular astrophysical interest, since they have been invoked as a potential progenitors of asymmetric Planetary Nebulae, and of at least a fraction of SN Type Ia - key cosmological distance indicators. Symbiotic systems provide great targets for studying accretion processes, jets, and outbursts in interacting binaries, and of focused wind accretion processes in particular. I will highlight and discuss the results from Chandra observations of several nearby symbiotic systems (e.g., CH Cyg, R Aqr, MWC 560) allowing for the first time mapping of the inter-binary and circumbinary X-ray environments at an unprecedented resolution reaching 0.1''.The key to obtaining the highest-resolution Chandra images is knowledge and modeling of the HRMA + instrumental PSFs (including modeling of artifacts at a sub-arcsecond scale), and using multi-scale restoration techniques, such as the EMC2 (Expectation through Markov Chain Monte Carlo) technique. The results show that using the highest available spatial resolution at X-ray wavelengths, combined with high-angular resolution UV/Optical and radio imaging, is key to understanding the mass transfer and accretion processes in these evolving dynamic systems.Chandra high-angular resolution imaging and spectroscopy results, combined with the results from joint HST and JVLA observations, have discovered dramatic changes in the spatial and spectral distribution of the emission in these interacting systems on time scales from days to years, including significant variability of the accretion rate on the white dwarf companion, and powerful outbursts, jets, and outflows. The observations show evidence for multiple ejections of material in these systems, likely originating from the accretion disk around the white dwarf, detected at scales of a few dozen to few thousands AUs from the binary. The mechanisms responsible for these multiple outbursts/jets are potentially related to massive outbursts in the mass donor giant star. 3-D hydrodynamical numerical models of the mass transfer between the components in these systems, including mass outbursts in the donor star and wind accretion by the compact accretor, have led to better understanding of the mechanisms causing the observed activity and the complex changes in the circumbinary environment.Given the observed variability of the Symbiotic systems on time scales of years, it is of great importance to continue to characterize their long-term dynamic evolution using high-resolution Chandra observations, combined with other multi-wavelength observations in the UV/Optical, radio, and IR, in order to understand the mechanisms that shape the complex environments in which the jets/outflows propagate and expand. This will lead toward a more complete picture of the activity in these wind accreting systems and of their complex environments at this stage of their evolutionary path..
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  • Vicky Kaspi
  • (McGill University)
  • Chandra and Neutron Stars
  • Chandra has been invaluable to the study of neutron stars in their diverseforms, from radio pulsars and their wind nebulae, to thermally cooling neutronstars, to magnetars in quiescence and in outburst, to the curious "centralcompact objects." Here we review the principal contributions Chandra has madeto this area of research, and consider what future results may be of interest.
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  • Dacheng Lin
  • (University of New Hampshire)
  • Three candidate magnetar-powered fast X-ray transients found from Chandra archival data
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  • Chandreyee Maitra
  • (Max Planck Institute for Extraterrestrial Physics)
  • Unveiling the intriguing nature of PSR J0855-4644 through a Chandra observation: Why no Gamma rays?
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  • Sera Markoff
  • (University of Amsterdam)
  • Chandra’s exquisite view of the accretion processes around black holes
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  • Rafael Martínez-Galarza
  • (Center for Astrophysics | Harvard & Smithsonian)
  • The Weirdest Objects in the Chandra Source Catalog 2.0. A Machine Learning Approach
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  • Alberto Masini
  • (Dartmouth College)
  • The Chandra Deep Wide Field Survey of the Bootes Field
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  • Michael McDonald
  • (MIT)
  • 10 Years of Chandra and the South Pole Telescope
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  • Brian McNamara
  • (University of Waterloo)
  • Cluster Atmospheres Unveiled by Chandra
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  • Kirpal Nandra
  • (MPE)
  • Status and first results from eROSITA
  • eROSITA was launched aboard the Spektr-RG (SRG) spacecraft from Baikonur, Kazakhstan on July 13th 2019. With SRG now at L2, eROSITA is currently in its commissioning phase. After a short series of calibration and performance verification observations, eROSITA, along with its sister instrument ART-XC, will perform a series of eight all sky X-ray surveys over four years. The eROSITA survey will be about 30 times more sensitive than ROSAT in the soft energy band (0.5-2 keV), while in the hard band (2-10 keV) it will provide the first ever true imaging survey of the whole sky. The design driving science is the detection of large samples of galaxy clusters, to constrain the cosmological parameters, including those associated with dark energy. eROSITA is also expected to yield a sample of around 3 million active galactic nuclei over a wide redshift range, which should revolutionize our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of other astrophysical phenomena, including compact objects, active stars and diffuse emission from hot plasma within our own and other galaxies. It will also open a new window into the time domain in the X-ray band. In this talk, the status of the mission and instrument will be reviewed, and early results presented.
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  • Kate Napier
  • (University of Michigan)
  • Probing the viability of CMB quenching for high-z jetted AGN
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  • Priyamvada Natarajan
  • (Yale University)
  • Unveiling black holes in the near and far universe
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  • Rachel Osten
  • (Space Telescope Science Institute & John Hopkins University)
  • Seeing Stars in a New Light: What Have We Learned from 20 Years of Investigations with Chandra, and What Do We Still Need to Learn?
  • Historian Frederic William Maitland wrote "We should always be aware that what now lies in the past once lay in the future". The occasion of Chandra's twenty years in orbit is an excellent opportunity to examine the future that is the now the past, and reflect on the amazing discoveries in stellar astrophysics enabled by the combination of Chandra's spectroscopic and spatial capabilities, multiplexed with short and long-term temporal information. Nearly every area of stellar astrophysics has been touched and advanced by Chandra's high energy measurements, from the winds of massive stars, to sleuthing details of coronal heating at the end of the main sequence, to deeper investigations of the jets, accretion, and complexity of young stars, to new insights into the later stages of stellar evolution. In this review I will touch upon some of Chandra's biggest "home runs" in the area of stellar astrophysics,pointing out how far we've come in our understanding, as well as laying out some of the new challenges for current and future high energy stellar investigations.
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  • Vaughn Parts
  • (Swarthmore College)
  • Modeling O star grating spectra to constrain the shock-heated plasma temperature distributions and mass-loss rates of their winds
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  • Daniel Patnaude
  • (Center for Astrophysics | Harvard & Smithsonian)
  • 20 Years of Cas A with the Chandra X-ray Observatory
  • Cassiopeia A is one of only a handful of young supernova remnants to exhibit time variations in thermal and nonthermal X-ray emission. Here, I will present results from a multiyear effort to study the evolution of this extraordinary object. With observations taken on a nearly yearly timescale, we are able to track the evolution of freshly shocked material as it interacts with the remnant's reverse shock, revealing previously unshocked and unseen ejecta. In addition to the observed changes in emission from shocked material, we also continue to observe fluctuations in nonthermal emission on both large and small spatial scales. I will discuss these observed changes in the context of the nonlinear diffusive shock acceleration of particles brought about by a highly amplified postshock magnetic field.
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  • George Pavlov
  • (Pennsylvania State University)
  • High-speed ejecta from the high-mass gamma-ray binary PSR B1259--63/LS 2883
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  • Ryan Pfeifle
  • (George Mason University)
  • Uncovering Buried Dual and Triple AGNs in Galaxy Mergers
  • Galaxy collisions, a ubiquitous phenomenon in the Universe, are predicted to be a critical avenue for galaxy and black hole growth and evolution. During a merger event, gravitational torques drive reservoirs of gas and dust toward the galactic cores, and these inflows are consequently accreted by the central supermassive black holes, which then manifest as active galactic nuclei (AGNs). Dual AGNs are expected to occur in late-stage mergers, where the black holes are predicted to experience their most rapid period of growth. In our recent Chandra investigation of 15 late-stage mergers preselected with WISE, we found dual AGNs or candidate duals in 8 out of 15 mergers, many of which show no evidence for AGNs in the optical. Our multiwavelength observations suggest that the buried AGNs in these mergers are highly absorbed, consistent with hydrodynamic simulations. One of these mergers, SDSS J0849+1114, was in fact a triple galaxy merger, and exhibited three nuclear X-ray sources detected by Chandra. Through a multiwavelength follow-up investigation – involving Large Binocular Telescope optical and NIR spectroscopy as well as NuSTAR hard X-ray observations – we demonstrate that SDSS J0849+1114 represents the most compelling case for a triple AGN in the literature. These investigations demonstrate that 1) optical studies miss a significant fraction of single and dual AGNs in advancement mergers where the AGNs are expected to be highly obscured, and 2) mid-infrared preselection is extremely effective at identifying dual and now even triple AGN candidates in late-stage mergers. Chandra has revolutionized our ability to identify and characterize black hole growth within galaxy mergers, and with its superior spatial resolution and sensitivity, Chandra has played a critical role in unveiling a population of dual and triple AGNs that may otherwise have remained undiscovered using extensive optical surveys alone.
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  • Gabriele Ponti
  • (Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Brera)
  • AGN and AGN feedback
  • Accretion onto black holes is intimately connected with thecreation of outflows in the form of jets and winds. It is well establishedthat such outflows can have a strong impact on the physics of the surroundingmedium as well as on the growth of the host galaxy. I will review the recentresult on AGN and AGN feedback going from powerful quasars to very lowaccretion rate, such as present at the center of the Milky Way.
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  • David Pooley
  • (Trinity University)
  • The Most Powerful Lenses in the Universe: Quasar Microlensing
  • Nature has given us a tool more powerful than any telescope we could build in the next several decades. Without Chandra we would not be able to utilize it, and we might not have even known it exists. This tool is the combination of strong gravitational lensing of a quasar by a galaxy ("macrolensing") and further lensing by the individual stars inside the galaxy ("microlensing"). It was Chandra observations of quadruply gravitationally lensed quasars which conclusively demonstrated that microlensing is occurring. Once established, microlensing was used as a tool, and Chandra observations were used to (1) place constraints on the sizes of quasar accretion disks, (2) determine how much of the lensing galaxies' matter content is in a smooth component and how much is composed of compact masses (e.g., stars, stellar remnants, primordial black holes, CDM sub-halos, and planets), and (3) calibrate the fundamental plane, providing a measurement of the stellar M/L, a fundamental astronomical quantity and something nearly impossible to measure beyond the solar neighborhood through any other means.
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  • Norbert Schartel
  • (ESA - ESAC)
  • 20th Launch Anniversary of XMM-Newton: Scientific Achievements and Future Perspectives
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  • Pat Slane
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Probing the Relics of Stellar Explosions with Chandra
  • Supernova explosions play a key role in regulating galactic chemistry, the temperature and pressure conditions in the ISM, the production of cosmic rays, and triggered star formation. The physics of the explosions and of the compact neutron stars or black holes produced in the core-collapse events probe the extremes of temperature and density, and the observable properties of the relics from these events depend crucially on our understanding of turbulence, magnetic fields, plasma instabilities, and the equation of state of ultradense matter.The wealth of observational data on supernova remnants and the nebulae produced by compact pulsars within SNRs contribute mightily to our understanding of the underlying physics. Because of the highly-energetic nature of these events, resulting in high temperatures and relativistic particles, X-ray observations provide a crucial role in these studies. The unique capabilities provided by Chandra's high angular resolution and spatially-resolved spectroscopy have resulted in breakthrough science in these areas. In this talk, I will provide a brief synopsis of the underlying physical principles of interest, and a summary of important Chandra contributions to these areas.
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  • Randall Smith
  • (Center for Astrophysics | Harvard & Smithsonian)
  • The Future of High Resolution Spectroscopy
  • High-resolution X-ray spectroscopy made great leaps with the launch of Chandra and XMM-Newton, which provided resolutions of 300-1000 (E/dE) over a broad bandpass, primarily for point sources. Although tragically short-lived, the microcalorimeter on Hitomi showed the power of non-dispersive high-resolution spectroscopy, again with R=300-1000, to reveal information about extended objects such as galaxy clusters and supernova remnants. The upcoming launch of XRISM (2022) will enable many more such observations, albeit with only modest (∼1 -FB) spatial resolution. ESABS Athena mission (2031 launch) will -A vastly expand these capabilities, providing higher spectral resolution (up to R∼2400 at 6 keV) with a much larger field of view and significantly improved (5 -FBB) spatial resolution. For point sources, the proposed Arcus mission would -A provide R∼2500 in the soft X-ray band with effective areas comparable to Hitomi. Lynx, a proposed new flagship for the 2030s, would significantly extend both calorimeter and grating spectroscopy capabilities. I will discuss some of opportunities and challenges facing the community as we prepare for these new missions.
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  • Bradford Snios
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Detection of Superluminal Motion in the X-Ray Jet of M87
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  • Malgosia Sobolewska
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Environment and growth of young extragalactic radio jets probed with X-rays
  • Formation and launching of relativistic jets is one manifestation of black hole activity. Jets impact the black hole surroundings and consequently affect further black hole feeding and growth. This coupling is believed to be essential to the idea of AGN-galaxy feedback. Theory predicted that young radio jets should be strong high-energy emitters. However, they proved to be relatively faint and observing them has been challenging before the Chandra and XMM-Newton era. Here, we discuss the most recent results for a sample of four Compact Symmetric Objects (CSO; radio structure sizes 2-16 pc and ages 100-400 years) based on the new high quality broadband radio-to-hard-X-ray/gamma-ray spectral energy distributions including Chandra, XMM-Newton, NuSTAR and Fermi/LAT data. For the first time, we have now means to test theoretical scenarios for the high energy emission of the young radio jets (radio lobes origin, shocked ISM, jet, disk corona). We were able to refute the radio lobes origin in at least one source. In addition, we find evidence to support the dichotomy of the CSO environment that we have recently discovered. This dichotomy may suggest that X-ray obscured CSOs have smaller radio sizes than X-ray unobscured CSOs with the same radio power. Thus, the environment may play a crucial role in regulating the early growth of the radio jets. Importantly, X-rays emitted by the X-ray absorbed CSO sub-population, in conjunction with the recent developments in the optical/IR and radio bands, offer new insights for understanding the structure and size of the AGN obscuring torus, as they provide information about the radiative processes and environment on the torus (parsec) scale. We discuss the implications of our results for the earliest stages of a radio galaxy evolution, high energy emission models of radio jets, diversity of the medium in which the jets expand, and jet-galaxy co-evolution.
  •  
  • Roberto Soria
  • (UCAS (Beijing))
  • Ultraluminous X-ray sources and nuclear black holes in the Virgo cluster spirals
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  • James Steiner
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Spins of supermassive black holes with X-ray timing observations of tidal disruption events (TDEs)
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  • Harvey Tananbaum
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Chandra’s Early Years (1963 – 1991)
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  • Wallace Tucker
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Discovery Years with Rocket
  •  
  • Georgios Vasilopoulos
  • (Yale University)
  • Ultraluminous X-ray pulsars: spin-evolution and super-orbital modulation during super-Eddington accretion
  •  
  • Alexey Vikhlinin
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Future of high-resolution X-ray imaging
  •  
  • Stephen Walker
  • (University of Alabama in Huntsville)
  • Unravelling the physics of the intracluster medium with cold fronts
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  • Q. Daniel Wang
  • (University of Massachusetts)
  • Large-scale Chandra Survey of the Galactic Central Region
  • Nuclear activity of a galaxy plays a key role in shaping its ecosystem. However, how such activity actually varies with time and affect the environment remains largely uncertain. Our Galaxy is a unique site where this issue can be studied over broad time and spatial ranges. To facilitate such a study, we have just completed a Chandra survey of the Galactic central 2 × 4 square degree field. This Chandra legacy survey will be used for years to come. In particular, the complete Chandra coverage of the field allows us to study the large-scale diffuse X-ray emission with minimal confusion from X-ray-absorbing features, as well as distinctly extended objects such as young supernova remnants and pulsar wind nebulae. We can then examine properties of various outstanding ionization/outflow phenomena observed in the region, as well as X-ray sources as a function of the Galactic latitude. We will present initial results from the survey.
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  • Qian Wang
  • (University of Utah)
  • Searching for X-ray Shock Fronts at Radio Relic Edges in PLCKESZ G200.9-28.2 and Abell 2345 with Chandra
  •  
  • Martin Weisskopf
  • (NASA MSFC)
  • Building the Observatory 1991-1999
  •  
  • Belinda Wilkes
  • (Center for Astrophysics | Harvard & Smithsonian)
  • Riccardo's Legacy in X-ray Astronomy: Chandra's Science
  • NASA's Chandra X-ray Observatory has revolutionized X-ray astronomy, a truly fitting legacy for Riccardo. Chandra's unique, sub-arcsecond spatial resolution, broad energy range and deep view of the Universe has been a game-changer across a broad range of astrophysics, and it continues to forge new paths as the science moves forward and as new facilities and their associated discoveries come on line. I will review highlights of Chandra science over the past 20 years, illustrating the depth, breadth and richness of the data and results. Topics will extend from our own solar system to the most distant super-massive black holes, from stars to clusters of galaxies, and beyond the electromagnetic spectrum to dark matter, and gravitational wave sources.
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  • Brian Williams
  • (NASA GSFC)
  • The Expansion of Tycho's Supernova Remnant
  • Perhaps no event in astronomical history changed the landscape more than the supernova of 1572 A.D., the remnant of which is now known as "Tycho's Supernova Remnant." No longer were the heavens fixed in permanence; the sky was shown to changing and unpredictable. Four centuries later, Chandra has observed Tycho's SNR over the course of multiple epochs, dating back to the first year of operation. With Chandra's sharp eyes, we can watch the remnant expand and directly measure the speed of the blast wave of the supernova as it races through the ISM, as well as the fluffy "tufts" of metal-rich ejecta that were once part of the star. In this talk, I will present results of such measurements, showing that despite its round appearance, Tycho's expansion isn't necessarily as symmetric as we might expect - the structure of the surrounding ISM is beginning to shape the evolution of the remnant. I will also show three-dimensional measurements of the velocity of dozens of ejecta knots, made by combining proper motions in the plane of the sky measured from Chandra images with Doppler shifts in the Chandra ACIS spectra. The velocity information of the ejecta knots favors some Type Ia explosion models over others, which has significant implications for how these supernovae explode across the universe.
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  • Scott Wolk
  • (Center for Astrophysics | Harvard & Smithsonian)
  • High Energy Diversity of Exoplanet Host Stars
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  • Yi-Jung Yang
  • (Institute of High Energy Physics, Chinese Academy of Sciences)
  • A Candidate Nuclear IMBH in a Blue Compact Dwarf Galaxy
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  • Shuo Zhang
  • (Boston University)
  • Fine Morphology of Galactic Center Non-thermal Filaments Revealed by Deep Chandra Observation