Chandra's First Decade of Discovery

Session 6: Supernova Remnants

X-Ray Studies of Supernova Remnants: The Persistence of Memory

Carles Badenes, Tel-Aviv University

The unprecedented capabilities of Chandra for spatially resolved spectroscopy have revolutionized our understanding of supernova remnants. I will review the fundamental open issues in core collapse and Type Ia supernova explosions, and the progress that has been made using X-ray observations of supernova remnants.

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New Deep X-ray and Radio Observations of G1.9+0.3

Kazimierz Borkowski, North Carolina State University
S.P.Reynolds (NCSU), D.A.Green (University of Cambridge), U.Hwang, I.Harrus, R.Petre (NASA/GSFC)

Chandra X-ray observations revealed G1.9+0.3 to be the youngest known Galactic supernova remnant (SNR), only ~ 100 yr old. Subsequent observations with the Very Large Array (VLA) confirmed this discovery. Both X-ray and radio emission are produced by relativistic electrons, accelerated in shocks with extreme (up to 14,000 km s-1) velocities, but their morphologies are strikingly different. A pronounced NE-SW radio asymmetry contrasts with a bipolar NW-SE X-ray emission that arises in shocks capable of accelerating electrons to ~ 10-100 TeV energies. Harder X-rays correlate with systematically varying X-ray brightness along the remnant's periphery. This may be interpreted in terms of the magnetic field obliquity dependence of the cosmic-ray acceleration efficiency, but observations available until now have not allowed for distinguishing between models with radically different field geometries. These models also fail to explain the strong NE-SW radio asymmetry. We present new deep Chandra and VLA observations that allow us to examine spatial morphologies and spectra of G1.9+0.3 in much greater detail than previously possible. We discuss how these observations advance our knowledge of particle acceleration in very fast SNR shocks.

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A Half-Megasecond Chandra Observation of the Oxygen-rich Supernova Remnant G292.0+1.8

Jae-Joon Lee, Pennsylvania State Univ.
Sangwook Park (Pennsylvania State Univ.), John Hughes (Rutgers), Patrick Slane (SAO), Bryan Gaensler (University of Sydney), Parviz Ghavamian (STScI), David Burrows (Pennsylvania State Univ.)

Our Chandra Large Project of the Galactic O-rich SNR G292.0+1.8 is one of the highlights for the core-collapse SNR studies in the 10-yr legacy of Chandra. We review the early results and report on the recent progress on our analysis of a deep 510 ks Chandra observation. G292.0+1.8 is a textbook example of remnants of core-collapse super novae, harboring a pulsar (J1124-5916) and a pulsar wind nebula, the reverse-shocked metal-rich ejecta material, and the shocked circumstellar wind. The X-ray characteristics of the shocked circumstellar wind shows that the progenitor star had experienced a massive mass loss during its late-stage evolution. A highly nonuniform distribution of thermodynamic conditions of the X-ray-emitting ejecta features suggest that the explosion was likely aspherical. We further reveal spectacular substructures of a torus, a jet, and an extended central compact nebula, all associated with the embedded pulsar. The observation shows a consistent picture of late-stage evolution of massive star, where it loses a significant amount of its initial mass as stellar wind and undergoes an aspheric explosion to leave a neutron star with high spatial velocity.

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SNR 1987A: Ten Years of Chandra Monitoring

Sangwook Park, Penn State
David Burrows (Penn State), Judith Racusin (Penn State), Svetozar Zhekov (Colorado), Richard McCray (Colorado), Daniel Dewey (MIT), Vikram Dwarkadas (Chicago), and Gordon Garmire (Penn State)

We have been observing the dynamical and spectral evolution of SNR 1987A with Chandra since 1999. As of 2009 July, we have performed 20 monitoring observations of SNR 1987A. We have also performed 4 deep grating spectroscopic observations. We here review the X-ray evolution of SNR 1987A over the last 10 yr, including updates from the recent observations. The current X-ray emission of SNR 1987A originates primarily from the shock interaction with complex density structures along the inner circumstellar ring, which results in a range of the shock velocities and plasma conditions. We find no evidence for the much-anticipated central point source. The latest data show that SNR 1987A continues to brighten, but probably at a lower rate than 5 yr ago. The radial expansion of the SNR has significantly slowed since ~2004, supporting the interpretation that the blast wave is entering the main body of the inner ring. Recently we transitioned from using the ACIS to using the HETG in our monitoring program. The upcoming X-ray light curves combined with high resolution spectroscopy will help us further study the details of the shock evolution in the context of the density/chemical structures of the equatorial stellar winds and the late-stage evolution history of SN 1987A's massive progenitor.

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Chandra Searches for Late-Time Jet Breaks in GRB X-ray Afterglows

David Burrows, Penn State University
G. Garmire (PSU), G. Ricker (MIT), M. Bautz (MIT), J. Nousek (PSU), D. Grupe (PSU), J. Racusin (PSU)

The Swift X-ray Telescope has now studied hundreds of X-ray afterglows of Gamma-Ray Bursts. One surprising finding is the apparent absence of jet breaks in the XRT light curves, suggesting that the Swift GRBs may have larger jet opening angles than those studied before the launch of Swift. We have undertaken a program of late-time observations of GRB afterglows by the Chandra X-ray Observatory to search for possible jet breaks at very late times, after the afterglow becomes too faint for Swift to monitor. These Chandra observations push the flux limits down by an order of magnitude, from ~2E-14 cgs to ~2E-15 cgs. I will report on the results of this on-going program, which has found very late jet breaks in some cases, and failed to find evidence of jet breaks to very late times in other afterglows. The results are consistent with the recent findings of Racusin et al., that suggest that some jet breaks occur at very late times but that the opening angles are typically still of order 5-10 degrees.

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