Background, Study Process, Workshp Objectives

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Spatially Varying X-ray Synchrotron Emission in SN 1006

A growing number of both galactic and extragalactic supernova remnants show non-thermal (non-plerionic) emission in the X-ray band. New synchrotron models, realized as SRESC and SRCUT in XSPEC 11, which use the radio spectral index and flux as inputs and include the full single-particle emissivity, have demonstrated that synchrotron emission is capable of producing the spectra of dominantly non-thermal supernova remnants with interesting consequences for residual thermal abundances and acceleration of particles. In addition, these models deliver a much better-constrained separation between the thermal and non-thermal components, whereas combining an unconstrained powerlaw with modern thermal models can produce a range of acceptable fits. While synchrotron emission can be approximated by a powerlaw over small ranges of energy, the synchrotron spectrum is in fact steepening over the X-ray band. Having demonstrated that the integrated spectrum of SN 1006, a remnant dominated by non-thermal emission, is well described by synchrotron models I now turn to spatially resolved observations of this well studied remnant. The synchrotron models make both spectral and spatial predictions, describing how the non-thermal emission varies across the remnant. Armed with spatially resolved non-thermal models and new thermal models such as VPSHOCK we can now dissect the inner workings of SN 1006.Comment: 4 pages, 4 figures. To appear in "Young Supernova Remnants" the 11th Annual October Maryland Astrophysics Conference AIP eds. Steve Holt and Una Hwan

Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

With the XMM-Newton and Chandra observatories, we detected two extremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, near IRS 7. These sources, designated as XB and XA, have X-ray absorption columns of ~3e23 cm-2 equivalent to AV ~180 mag. They are associated with the VLA centimeter radio sources 10E and 10W, respectively. XA is the counterpart of the near-infrared source IRS 7, whereas XB has no K-band counterpart above 19.4 mag. This indicates that XB is younger than typical Class I protostars, probably a Class 0 protostar or in an intermediate phase between Class 0 and Class I. The X-ray luminosity of XB varied between 29<log LX <31.2 ergs s-1 on timescales of 3-30 months. XB also showed a monotonic increase in X-ray brightness by a factor of two in 30 ksec during an XMM-Newton observation. The XMM-Newton spectra indicate emission from a hot plasma with kT ~3-4 keV and also show fluorescent emission from cold iron. Though the X-ray spectrum from XB is similar to flare spectra from Class I protostars in luminosity and temperature, the light curve does not resemble the lightcurves of magnetically generated X-ray flares because the variability timescale of XB is too long and because variations in X-ray count rate were not accompanied by variations in spectral hardness. The short-term variation of XB may be caused by the partial blocking of the X-ray plasma, while the month-long flux enhancement may be driven by mass accretion.Comment: 26 pages, 8 figures, To be published in ApJ in April 200

Suzaku wide-band observations of SN 1006

We report on the wide band spectra of SN 1006 as observed by Suzaku. Thermal and nonthermal emission are successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission cannot be reproduced by a simple power-law model but needs a roll-off at 5.7$\times 10^{16}$ Hz = 0.23 keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also have placed the most stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.Comment: 16 pages, 8 figures, PASJ, in pres

A Smoking Gun in the Carina Nebula

The Carina Nebula is one of the youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for ~30 years. The soft X-ray spectrum, consistent with kT ~128 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a ~1e6-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular Eta Carinae, are coeval. This result suggests that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star may be responsible for remnants of high energy activity seen in multiple wavelengths.Comment: 9 pages, 3 figures, accepted for publication to ApJ

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements