A Detailed Observation of a LMC Supernova Remnant DEM L241 with XMM-Newton

We report on an {\it XMM-Newton} observation of the supernova remnant (SNR) \object{DEM L241} in the Large Magellanic Cloud. In the soft band image, the emission shows an elongated structure, like a killifish, with a central compact source. The compact source is point-like, and named as XMMU J053559.3$-$673509. The source spectrum is well reproduced with a power-law model with a photon index of $\Gamma = 1.57$ (1.51--1.62) and the intrinsic luminosity is $2.2\times 10^{35} \mathrm{ergs s^{-1}}$ in the 0.5--10.0 keV band, with the assumed distance of 50 kpc. The source has neither significant coherent pulsations in $2.0\times 10^{-3}$ Hz--8.0 Hz, nor time variabilities. Its luminosity and spectrum suggest that the source might be a pulsar wind nebula (PWN) in DEM L241. The spectral feature classifies this source into rather bright and hard PWN, which is similar to those in Kes 75 and B0540$-$693. The elongated diffuse structure can be divided into a ``Head'' and ``Tail'', and both have soft and line-rich spectra. Their spectra are well reproduced by a plane-parallel shock plasma ({\it vpshock}) model with a temperature of 0.3--0.4 keV and over-abundance in O and Ne and a relative under-abundance in Fe. Such an abundance pattern and the morphology imply that the emission is from the ejecta of the SNR, and that the progenitor of DEM L241 is a very massive star, more than 20 M\sun. This result is also supported by the existence of the central point source and an OB star association, LH 88. The total thermal energy and plasma mass are $\sim 4\times 10^{50}$ ergs and $\sim 200$ M\sun, respectively.Comment: 9 pages, 11 figures, A&A, in press (full-resolution version is available at http://cosmic.riken.jp/bamba/Aya-Bamba_DEML241.pdf

Degradation of Aqueous 2,6-Dibromo-phenol Solution by In-Liquid Dielectric Barrier Microplasma

Abstract Degradation of 2,6-dibromophenol (2,6-DBP) in the aqueous solution was studied using dielectric barrier discharge in micro-bubbles. Experimental comparison of working gas Ar, N2, O2, and air showed that oxygen and air plasma efficiently decomposed 2,6-DBP to bromide ion, and inorganic carbon. The molecular orbital model was applied in the analysis of the degradation in electrophilic, nucleophilic, and radical reactions

Low-background prebunching system for heavy-ion beams at the Tokai radioactive ion accelerator complex

A novel beam-bunching technique has been implemented at a heavy-ion linear accelerator facility by installing a compact two-gap prebuncher and a multilayer beam chopper. A pulsed beam of 2 to 4 MHz, having kinetic energy up to 1.1  MeV/u, is realized by bunching a 2  keV/u continuous beam just upstream of the linac. Around 40% of the continuous beam particles are successively gathered in a single microbunch with a time width of around 15 ns in full width at one-tenth maximum. The number of background beam particles over 250 ns just before the bunched beam is well suppressed to less than 10^{-4} of the number of bunched particles. This technique has been adopted to generate intense α-particle beams for nuclear astrophysics experiments