Fermi LAT Observations of Supernova Remnants Interacting with Molecular Clouds: W41, MSH 17-39, and G337.0-0.1

We report the detection of gamma-ray emission coincident with three supernova remnants (SNRs) using data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. W41, MSH 17-39, and G337.0-0.1 are SNRs known to be interacting with molecular clouds, as evidenced by observations of hydroxyl (OH) maser emission at 1720 MHz in their directions and other observational information. SNR shocks are expected to be sites of cosmic ray acceleration, and clouds of dense material can provide effective targets for production of gamma-rays from neutral pion-decay. The observations reveal unresolved sources in the direction of G337.0-0.1, and MSH 17-39, and an extended source coincident with W41. We model their broadband emission (radio to gamma-ray) using a simple one-zone model, and after considering scenarios in which the MeV-TeV sources originate from either neutral pion-decay or leptonic emission, we conclude that the gamma-rays are most likely produced through the hadronic channel.Comment: 9 pages, 11 figures, accepted for publication in Ap

A Chandra View Of Nonthermal Emission In The Northwestern Region Of Supernova Remnant RCW 86: Particle Acceleration And Magnetic Fields

The shocks of supernova remnants (SNRs) are believed to accelerate particles to cosmic ray (CR) energies. The amplification of the magnetic field due to CRs propagating in the shock region is expected to have an impact on both the emission from the accelerated particle population, as well as the acceleration process itself. Using a 95 ks observation with the Advanced CCD Imaging Spectrometer (ACIS) onboard the Chandra X-ray Observatory, we map and characterize the synchrotron emitting material in the northwestern region of RCW 86. We model spectra from several different regions, filamentary and diffuse alike, where emission appears dominated by synchrotron radiation. The fine spatial resolution of Chandra allows us to obtain accurate emission profiles across 3 different non-thermal rims in this region. The narrow width (l = 10''-30'') of these filaments constrains the minimum magnetic field strength at the post-shock region to be approximately 80 {\mu}G.Comment: 7 pages, 3 figures, submitted for publication at the Astrophysical Journa

Vibration Isolation Design for the Micro-X Rocket Payload

Micro-X is a NASA-funded, sounding rocket-borne X-ray imaging spectrometer that will allow high precision measurements of velocity structure, ionization state and elemental composition of extended astrophysical systems. One of the biggest challenges in payload design is to maintain the temperature of the detectors during launch. There are several vibration damping stages to prevent energy transmission from the rocket skin to the detector stage, which causes heating during launch. Each stage should be more rigid than the outer stages to achieve vibrational isolation. We describe a major design effort to tune the resonance frequencies of these vibration isolation stages to reduce heating problems prior to the projected launch in the summer of 2014.Comment: 6 pages, 7 figures, LTD15 Conference Proceeding

Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

The SuperCDMS experiment in the Soudan Underground Laboratory searches for dark matter with a 9-kg array of cryogenic germanium detectors. Symmetric sensors on opposite sides measure both charge and phonons from each particle interaction, providing excellent discrimination between electron and nuclear recoils, and between surface and interior events. Surface event rejection capabilities were tested with two [superscript 210] Pb sources producing ∼130 beta decays/hr. In ∼800 live hours, no events leaked into the 8–115 keV signal region, giving upper limit leakage fraction 1.7 × 10[superscript −5] at 90% C.L., corresponding to < 0.6 surface event background in the future 200-kg SuperCDMS SNOLAB experiment.United States. Dept. of Energy (Contract No. DE-AC03-76SF00098)United States. Dept. of Energy (Contract No. DE-FG02-92ER40701)United States. Dept. of Energy (Contract No. DE-FG02-94ER40823)United States. Dept. of Energy (Contract No. DE-FG03-90ER40569)United States. Dept. of Energy (Contract No. DE-FG03-91ER40618)United States. Dept. of Energy (Contract No. DE-SC0004022)National Science Foundation (U.S.) (Grant No. AST-9978911)National Science Foundation (U.S.) (Grant No. NSF-0847342)National Science Foundation (U.S.) (Grant No. PHY-1102795)National Science Foundation (U.S.) (Grant No. NSF-1151869)National Science Foundation (U.S.) (Grant No. PHY-0542066)National Science Foundation (U.S.) (Grant No. PHY-0503729)National Science Foundation (U.S.) (Grant No. PHY-0503629)National Science Foundation (U.S.) (Grant No. PHY-0503641)National Science Foundation (U.S.) (Grant No. PHY-0504224)National Science Foundation (U.S.) (Grant No. PHY-0705052)National Science Foundation (U.S.) (Grant No. PHY-0801708)National Science Foundation (U.S.) (Grant No. PHY-0801712)National Science Foundation (U.S.) (Grant No. PHY-0802575)National Science Foundation (U.S.) (Grant No. PHY-0847342)National Science Foundation (U.S.) (Grant No. PHY-0855299)National Science Foundation (U.S.) (Grant No. PHY-0855525)National Science Foundation (U.S.) (Grant No. PHY-1205898

Constraining Explosion Type of Young Supernova Remnants Using 24 Micron Emission Morphology

Determination of the explosion type of supernova remnants (SNRs) can be challenging, as SNRs are hundreds to thousands of years old and supernovae (SNe) are classified based on spectral properties days after explosion. Previous studies of thermal X-ray emission from Milky Way and Large Magellanic Cloud (LMC) SNRs have shown that Type Ia and core-collapse (CC) SNRs have statistically different symmetries, and thus these sources can be typed based on their X-ray morphologies. In this paper, we extend the same technique, a multipole expansion technique using power ratios, to infrared (IR) images of SNRs to test whether they can be typed using the symmetry of their warm dust emission as well. We analyzed archival Spitzer Space Telescope Multiband Imaging Photometer (MIPS) 24 micron observations of the previously used X-ray sample, and we find that the two classes of SNRs separate according to their IR morphologies. The Type Ia SNRs are statistically more circular and mirror symmetric than the CC SNRs, likely due to the different circumstellar environments and explosion geometries of the progenitors. Broadly, our work indicates that the IR emission retains information of the explosive origins of the SNR and offers a new method to type SNRs based on IR morphology.Comment: 6 pages, 4 figures; accepted by ApJ

A DECADE-BASELINE STUDY OF THE PLASMA STATES OF EJECTA KNOTS IN CASSIOPEIA A

We present the analysis of 21 bright X-ray knots in the Cassiopeia A supernova remnant from observations spanning 10 yr. We performed a comprehensive set of measurements to reveal the kinematic and thermal state of the plasma in each knot, using a combined analysis of two high energy resolution High Energy Transmission Grating (HETG) and four medium energy resolution Advanced CCD Imaging Spectrometer (ACIS) sets of spectra. The ACIS electron temperature estimates agree with the HETG-derived values for approximately half of the knots studied, yielding one of the first comparisons between high resolution temperature estimates and ACIS-derived temperatures. We did not observe the expected spectral evolution—predicted from the ionization age and density estimates for each knot—in all but three of the knots studied. The incompatibility of these measurements with our assumptions has led us to propose a dissociated ejecta model, with the metals unmixed inside the knots, which could place strong constraints on supernova mixing models.United States. National Aeronautics and Space Administration (Award NNX10AE25G)National Science Foundation (U.S.) (Partnerships in Astronomy & Astrophysics Research and Education Grant AST-0849736)United States. National Aeronautics and Space Administration (Earth and Space Science Fellowship)United States. National Aeronautics and Space Administration (Harriet Jenkins Predoctoral Fellowship Program)Vanderbilt University (Provost Graduate Fellowship

SuperCDMS Cold Hardware Design

We discuss the current design of the cold hardware and cold electronics to be used in the upcoming SuperCDMS Soudan deployment. Engineering challenges associated with such concerns as thermal isolation, microphonics, radiopurity, and power dissipation are discussed, along with identifying the design changes necessary for SuperCDMS SNOLAB. The Cryogenic Dark Matter Search (CDMS) employs ultrapure 1-inch thick, 3-inch diameter germanium crystals operating below 50 mK in a dilution cryostat. These detectors give an ionization and phonon signal, which gives us rejection capabilities regarding background events versus dark matter signals.United States. Dept. of Energy (Grant DEAC02-76SF00515)United States. Dept. of Energy (Contract DC-AC02-07CH11359)National Science Foundation (U.S.) (Awards 0705052, 0902182, 1004714 and 0802575

Progress in the Development of Mo-Au Transition-Edge Sensors for X-Ray Spectroscopy

X-ray microcalorimeters using transition-edge sensors (TES) show great promise for use in astronomical x-ray spectroscopy. We have obtained very high energy resolution (2.8 electronvolts at 1.5 kiloelectronvolts and 3.7 electronvolts at 3.3 kiloelectronvolts) in a large, isolated TES pixel using a Mo/Au proximity-effect bilayer on a silicon nitride membrane. We will discuss the performance and our characterization of that device. In order to be truly suitable for use behind an x-ray telescope, however, such devices need to be arrayed with a pixel size and focal-plane coverage commensurate with the telescope focal length and spatial resolution. Since this requires fitting the TES and its thermal link, a critical component of each calorimeter pixel, into a far more compact geometry than has previously been investigated, we must study the fundamental scaling laws in pixel optimization. We have designed a photolithography mask that will allow us to probe the range in thermal conductance that can be obtained by perforating the nitride membrane in a narrow perimeter around the sensor. This mask will also show the effects of reducing the TES area. Though we have not yet tested devices of the compact designs, we will present our progress in several of the key processing steps and discuss the parameter space of our intended investigations