GeV Analysis of Mixed Morphology Supernova Remnants Interacting with Molecular Clouds

The first remnants detected by the Fermi Gamma-ray Space Telescope were of the type of mixed-morphology supernova remnants interacting with molecular clouds. In this paper we are presenting preliminary results of the gamma-ray analysis of 4 selected mixed morphology remnants, G359.1-0.5, G337.8-0.1, G001.0-0.1, and G346.6-0.2, as well as G349.7+0.2, in the 0.2 - 300 GeV energy range from the data collected by Fermi Gamma-ray Space Telescope for 3 years. G359.1-0.5, G337.8-0.1, and G349.7+0.2 were all detected with significances above 5 sigma. The excess distribution of G359.1-0.5 shows extended gamma-ray emission, which coincides with the TeV gamma-ray source HESS J1745-303. G337.8-0.1 also shows an extended nature.Comment: High Energy Gamma-Ray Astronomy: 5th International Meeting on High Energy Gamma-Ray Astronom

Searching for Overionized Plasma in the Gamma-ray Emitting Supernova Remnant G349.7++0.2

G349.7$+$0.2 is a supernova remnant (SNR) expanding in a dense medium of molecular clouds and interacting with clumps of molecular material emitting gamma rays. We analyzed the gamma-ray data of Large Area Telescope on board Fermi Gamma Ray Space Telescope and detected G349.7$+$0.2 in the energy range of 0.2$-$300 GeV with a significance of $\sim$13$\sigma$ showing no extended morphology. Modeling of the gamma-ray spectrum revealed that the GeV gamma-ray emission dominantly originates from the decay of neutral pions, where the protons follow a broken power-law distribution with a spectral break at $\sim$12 GeV. To search for features of radiative recombination continua in the eastern and western regions of the remnant, we analyzed the Suzaku data of G349.7$+$0.2 and found no evidence for overionized plasma. In this paper we discuss possible scenarios to explain the hadronic gamma-ray emission in G349.7$+$0.2 and the mixed morphology nature of this SNR.Comment: 10 pages, 7 figures; accepted by ApJ. arXiv admin note: text overlap with arXiv:1406.217

Recombining Plasma in the Gamma-ray Emitting Mixed-Morphology Supernova Remnant 3C 391

A group of middle-aged mixed-morphology (MM) supernova remnants (SNRs) interacting with molecular clouds (MC) has been discovered as strong GeV gamma-ray emitters by Large Area Telescope on board Fermi Gamma Ray Space Telescope (Fermi-LAT). The recent observations of the Suzaku X-ray satellite have revealed that some of these interacting gamma-ray emitting SNRs, such as IC443, W49B, W44, and G359.1-0.5, have overionized plasmas. 3C 391 (G31.9+0.0) is another Galactic MM SNR interacting with MC. It was observed in GeV gamma rays by Fermi-LAT as well as in the 0.3 $-$ 10.0 keV X-ray band by Suzaku. In this work, 3C 391 was detected in GeV gamma rays with a significance of $\sim$ 18 $\sigma$ and we showed that the GeV emission is point-like in nature. The GeV gamma-ray spectrum was shown to be best explained by the decay of neutral pions assuming that the protons follow a broken power-law distribution. We revealed radiative recombination structures of silicon and sulfur from 3C 391 using Suzaku data. In this paper we discuss the possible origin of this type of radiative plasma and hadronic gamma rays.Comment: 10 pages, 7 figures; accepted by Ap

The energy spectrum of very high energy gamma rays from the Crab Nebula as measured by the H.E.S.S. array

Das Thema dieser Arbeit ist die fuer das HEGRA Experiment entwickelte Rekonstruktions-Algoritmen, die Geometry und Energie von hochenergetischen kosmischen Gamma-Strahlen zu rekonstruieren, in die H.E.S.S. software Umgebung zu implementieren und das nicht-gepulste Energie-Spektrum des Krebsnebels zwischen Energien von 300 GeV und 20 TeV zu bestimmen. Dafuer wurden die ersten stereoskopischen Daten von Oktober und November 2003 mit einer 3 Teleskope-Konfiguration des H.E.S.S. Systems der Phase-I verwendet. Die Phase-I des H.E.S.S. Systems wurde im Dezember 2003 fertiggestellt, nachdem das vierte Teleskop in Betrieb genommen wurde. Die Rekonstruktionsalgorithmen wurden mit Monte Carlo Simulationen fuer die vollstaendige Phase-I des Teleskop-Systems getestet. Die Aufloesung fuer die rekonstruierte Richtung und Energie der einzelnen gamma-Ereignisse sind 0.15 Grad und 14 Prozent bei 45 Grad Zenitwinkel. Die Daten des Krebsnebels, die eine Wobble-Versetzung von +-0.5 Grad and +-1.0 Grad haben und die im Zenitwinkel-Bereich von 45 Grad bis 50 Grad fuer 4 Stunden beobachtet wurden, geben ein Signal von 50 Standardabweichungen. Das differentielle Energiespektrum des Krebsnebels zwischen 450 GeV und 20 TeV nach den Schnitten ist (dN / dE) = (3.37+-0.47)*10^{-11}*E^{-2.59+-0.12} cm^{-2} s^{-1} TeV^{-1}. Der integrierte Fluss oberhalb 1 TeV ist (2.11+-0.29)*10^{-11} cm^{-2} s^{-1}. Diese Resultate sind konsistent mit Messungen anderer Experimente, speziell von HEGRA und Whipple. Die Resultate stimmen mit den Erwartungen der synchroton self-Compton Modelle fuer den TeV Emissionbereich ueberein. Das magnetische Feld in der Region, wo die TeV gamma-Strahlen vermutlich entstehen, wird zu 0.18+-0.01 mG bestimmt. Die Resultate dieser Arbeit zeigen die Leistungsfaehigkeit des H.E.S.S. Teleskop-Systems.The goal of this thesis is to implement the methods developed for the HEGRA experiment to reconstruct the geometry and energy of the air-showers induced by the cosmic high-energy gamma rays into the software environment of the H.E.S.S. experiment. Furthermore, using the implemented algorithms, a search for the unpulsed emission is aimed in the energy range between 300 GeV and 20 TeV from the Crab Nebula using the first stereoscopic data taken during October and November 2003 with the 3 telescope configuration of the H.E.S.S. array in Phase-I. The Phase-I of the H.E.S.S. array was completed in December 2003 by the addition of the fourth telescope. By testing the reconstruction algorithms of a complete Phase-I H.E.S.S. array with Monte Carlo simulations, it is found that the resolution of the reconstructed direction and energy of a gamma-ray event from a zenith angle of 45 degrees is around 0.15 degrees and 14 percent, respectively. The data on the Crab Nebula including runs with wobble offset of +-0.5 degrees and +-1.0 degrees is collected at zenith angles from 45 degrees to 50 degrees for a total of 4 hours and gives a background subtracted signal of about 50 standard deviations. The differential energy spectrum of the unpulsed gamma-ray emission from the Crab Nebula is found to be (dN / dE) = (3.37+-0.47)*10^{-11}*E^{-2.59+-0.12} cm^{-2} s^{-1} TeV^{-1} between 450 GeV and 20 TeV after all cuts. The integral flux above 1 TeV is (2.11+-0.29)*10^{-11} cm^{-2} s^{-1}. These results are consistent with the results published by other experiments, in particular HEGRA and Whipple. The results agree well with the expectation from synchrotron self-Compton models for TeV emission range. The magnetic field in the region, where TeV gamma rays are produced, is found to be 0.18+-0.01 mG. This result agrees with the magnetic field values deduced by the models. The results obtained for the Crab Nebula in this thesis demonstrate the performance of the H.E.S.S. array

Suzaku and Fermi observations of the supernova remnant G1.9+0.3

We present results from the observation of the supernova remnant (SNR) G1.9 + 0.3, which is the youngest known SNR in the Milky Way, with the X-ray imaging spectrometer (XIS) on board Suzaku. We investigate the nature of the X-ray emission and compare our results with the previous X-ray studies. Additionally, we present the analysis results of the GeV gamma-ray data taken for about 6 years by the Large Area Telescope on board Fermi and discuss these results in the framework of existing gamma-ray emission scenarios. (C) 2015 COSPAR. Published by Elsevier Ltd. All rights reserved

Suzaku analysis of the supernova remnant G306.3-0.9 and the gamma-ray view of its neighbourhood

We present an investigation of the supernova remnant (SNR) G306.3-0.9, using archival multiwavelength data. The Suzaku spectra are well described by two-component thermal plasma models: the soft component is in ionization equilibrium and has a temperature similar to 0.59 keV, while the hard component has temperature similar to 3.2 keV and ionization time-scale similar to 2.6 x 10(10) cm(-3) s. We clearly detected Fe K-shell line at energy of similar to 6.5 keV from this remnant. The overabundances of Si, S, Ar, Ca and Fe confirm that the X-ray emission has an ejecta origin. The centroid energy of the Fe K line supports that G306.3-0.9 is a remnant of a Type Ia supernova (SN) rather than a core-collapse SN. The GeV gamma-ray emission from G306.3-0.9 and its surrounding were analysed using about 6-yr of Fermi data. We report about the non-detection of G306.3-0.9 and the detection of a new extended gamma-ray source in the south-west of G306.3-0.9 with significance of similar to 13 sigma. We discuss several scenarios for these results with the help of data from other wavebands to understand the SNR and its neighbourhood

Locating the TeV gamma-rays from the shell regions of Cassiopeia A

We have analyzed Chandra X-ray data from different parts of the shell of young supernova remnant (SNR) in the energy range of 0.7 - 8 keV. We observed that X-ray flux level varies over different shell regions of the source. Implications of X-ray observation will be discussed here. We also analyzed Fermi-LAT data in the energy range 0.5 - 50 GeV for the source. The differential spectrum obtained in this way fits with simple power-law. We also present here multi-wavelength modeling of the source considering archival radio and TeV data along with Chandra and Fermi-LAT data

A Suzaku X-ray study of the mixed-morphology supernova remnant Kes 69 and searching for its gamma-ray counterpart

Kes 69 is a mixed-morphology (MM) supernova remnant (SNR) that is known to be interacting with molecular clouds based on 1720 MHz hydroxyl (OH) maser emission observations in the northeastern and southeastern regions. We present an investigation of Kes 69 using similar to 67 ks Suzaku observation. The X-ray spectrum of the whole SNR is well fitted by a non-equilibrium ionization model with an electron temperature of kT(e) similar to 2.5 keV, ionization time-scale of tau similar to 4.1 x 10(10) cm(-3) s and absorbing column density of N-II similar to 3.1 x 10(22) cm(-2). We clearly detected the Fe-K alpha line at similar to 6.5 keV in the spectra. The plasma shows slightly enhanced abundances of Mg, Si, S, and Fe indicating that the plasma is likely to be of ejecta origin. We find no significant feature of a recombining plasma in this SNR. In order to characterize radial variations in the X-ray spectral parameters, we also analyse annular regions in the remnant. We investigate the explosive origin of Kes 69 and favour the core-collapse origin. Additionally, we report a lack of significant gamma-ray emission from Kes 69, after analysing the GeV gamma-ray data taken for about 9 yr by the Large Area Telescope on board Fermi. Finally, we discuss the properties of Kes 69 in the context of other interacting MM SNRs