Detection of highly ionized O and Ne absorption lines in the X-ray spectrum of 4U1820-303 in the globular cluster, NGC 6624

We searched for absorption lines of highly ionized O and Ne in the energy spectra of two Low-mass X-ray binaries, 4U1820-303 in the globular cluster NGC6624 and Cyg X-2, observed with the Chandra LETG, and detected O VII, O VIII and Ne IX absorption lines for 4U1820-303. The equivalent width of the O VII K alpha line was 1.19 +0.47/-0.30 eV (90 % errors) and the significance was 6.5 sigma. Absorption lines were not detected for Cyg X-2 with a 90 % upper limit on the equivalent width of 1.06 eV for O VII K alpha. The absorption lines observed in 4U1820-303 are likely due to hot interstellar medium, because O will be fully photo-ionized if the absorbing column is located close to the binary system. The velocity dispersion is restricted to b = 200 - 420 km/s from consistency between O VII K alpha and K beta lines, Ne/O abundance ratio, and H column density. The average temperature and the O VII density are respectively estimated to be log(T[K]) = 6.2 - 6.3 and n(OVII) = (0.7 - 2.3) x 10^{-6} cm^{-3}. The difference of O VII column densities for the two sources may be connected to the enhancement of the soft X-ray background (SXB) towards the Galactic bulge region. Using the polytrope model of hot gas to account for the SXB we corrected for the density gradient and estimated the midplane O VII density at the solar neighborhood. The scale height of hot gas is then estimated using the AGN absorption lines. It is suggested that a significant portion of both the AGN absorption lines and the high-latitude SXB emission lines can be explained by the hot gas in our Galaxy.Comment: Accepted for publication in ApJ. 7 pages, 9 eps figure

O and Ne K absorption edge structures and interstellar abundance towards Cyg X-2

We have studied the O and Ne absorption features in the X-ray spectrum of Cyg X-2 observed with the Chandra LETG. The O absorption edge is represented by the sum of three absorption-edge components within the limit of the energy resolution and the photon counting statistics. Two of them are due to the atomic O; their energies correspond to two distinct spin states of photo-ionized O atoms. The remaining edge component is considered to represent compound forms of oxide dust grains. Since Cyg X-2 is about 1.4 kpc above the galactic disk, the H column densities can be determined by radio (21 cm and CO emission line) and H alpha observations with relatively small uncertainties. Thus the O abundance relative to H can be determined from the absorption edges. We found that the dust scattering can affect the apparent depth of the edge of the compound forms. We determined the amplitude of the effect, which we consider is the largest possible correction factor. The ratio of column densities of O in atomic to compound forms and the O total abundance were respectively determined to be in the range 1.7^{+3.0}_{-0.9} to 2.8^{+5.1}_{-1.5} (ratio), and 0.63 +/- 0.12 solar to 0.74 +/- 0.14 solar (total), taking into account the uncertainties in the dust-scattering correction and in the ionized H column density. We also determined the Ne abundance from the absorption edge to be 0.75 +/- 0.20 solar. These abundance values are smaller than the widely-used solar values but consistent with the latest estimates of solar abundance.Comment: 20 pages, 3 figures, AASTeX format. Accepted for publication in Ap

Toward new frontiers : Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams

金沢大学理工研究域数物科学系超伝導遷移端マイクロカロリメータ(TES)は，非分散でありながら回折格子に匹敵する高いエネルギー分解能を実現するX線検出器である．遮蔽窓に穴を開けて安定に動作させることができれば，中性粒子計測を含め応用範囲が格段に広がることが期待される．本研究では，3次元の電磁界・熱シミュレーション計算と実測を駆使して最適なシールド環境を実現し，最終的には遮蔽窓なしでTESを安定動作させる方法論の確立を目指す．これによりTES応用の基盤を強化し，TESカロリメータを中性粒子計測を含む他の分野での最先端計測に生せるようにする．これはまた，初期宇宙観測等，天文観測のブレークスルーにも繋がることが期待される．概要3次元電磁場シミュレーションにより，任意の磁気シールド形状において強磁性体・超伝導体，静磁場・高周波磁場の計算ができるようになった．超伝導体の場合は，完全導体もしくは非透磁率の非常に小さな材質として扱う．例えば超伝導体の磁気シールドでは開口部にメッシュを入れることで遮蔽効果を改善できること，その違いはシールド外で排除できる磁束の違いで説明されることが理解できた．薄いフィルタに関してはメッシュの切り方に工夫が必要であり，フィルタを厚み0の2次元モデルとすることで取り扱うことができるようになった．並行して，ホール素子を用いた磁場の測定を行ない，シミュレーション計算結果と比較を行なった．磁場中に強磁性体シールド材の平板を置いてその周辺の磁場を測定し，計算結果と比較することにより，シールド材の比透磁率を評価することができるようになった．また実際にTES型X線マイクロカロリメータの動作に使用している磁気シールドに対して極低温下でホール素子を用いて磁場測定を行ない，シミュレーション計算結果と比較を行なった．磁場に対する感度は10 mT程度しか実現できなかったが，その範囲で実測と計算結果は概ね一致し，磁気シールドの飽和を含めて再現できていることを確認した．以上の成果を踏まえ，他のグループのTES型X線マイクロカロリメータ用の磁気シールドの設計検討を支援した．これは関連分野における基盤技術として貢献できていることを示しており，本研究の主要な目的を達成できた．また，今後のＸ線天体の撮像精密分光観測を念頭において，搭載機器の開発と観測的研究も進めた．研究課題/領域番号:19H05189, 研究期間(年度):2019-04-01 – 2021-03-31出典：研究課題「中性粒子計測における超伝導転移端検出器の安定動作に向けた基盤構築」課題番号19H05189（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PUBLICLY-19H05189/）を加工して作

Lithium production on a low-mass secondary in a black hole soft X-ray transient

We examine production of Li on the surface of a low-mass secondary in a black hole soft X-ray transient (BHSXT) through the spallation of CNO nuclei by neutrons which are ejected from a hot (> 10 MeV) advection-dominated accretion flow (ADAF) around the black hole. Using updated binary parameters, cross sections of neutron-induced spallation reactions, and mass accretion rates in ADAF derived from the spectrum fitting of multi-wavelength observations of quiescent BHSXTs, we obtain the equilibrium abundances of Li by equating the production rate of Li and the mass transfer rate through accretion to the black hole. The resulting abundances are found to be in good agreement with the observed values in seven BHSXTs. We note that the abundances vary in a timescale longer than a few months in our model. Moreover, the isotopic ratio Li6/Li7 is calculated to be about 0.7--0.8 on the secondaries, which is much higher than the ratio measured in meteorites. Detection of such a high value is favorable to the production of Li via spallation and the existence of a hot accretion flow, rather than an accretion disk corona system in quiescent BHSXT.Comment: 4 pages, 3 figures, and 2 tables, submitted to Astrophyscal Jounal Letter

宇宙X線観測用精密分光器を応用した可搬型の微量環境放射線計測装置の試作

金沢大学理工研究域数物科学系今年度は小型断熱消磁冷凍機の更なる性能向上とX線マイクロカロリメータ動作に取り組んだ。まず冷凍機に関しては、放射シールドや配線の這い回しを徹底的に見直し、冷却環境の改善を目指した。その結果、0.084Kまで冷え、温度0.1Kを7時間以上保持できるようになった。また、計測装置の電気的な接地方法についても見直し、9μK(RMS値)の温度安定度を実現できるようになった。これらはいずれもX線マイクロカロリメータ動作を十分に実現できる性能である。次に、温度制御を行ないながら超伝導遷移端温度計(TES)の超伝導遷移の際の抵抗-温度特性を評価した。計測そのものは昨年度も実施しているが、温度制御をかけながら測定を行なうことができるようになった点が大きな改善点である。検出器ステージに磁気シールドを施し、センサ動作に向けた環境を整えた。TES温度計の評価の結果、小型断熱消磁冷凍機の環境できちんと超伝導転移することが確認できた。ただし、過去の測定では0.02K程度の温度幅で転移していたものが0.05K程度に広がっており、センサに外部磁場等の影響が若干残っているということが明らかになった。これについては今後さらなる改良が必要である。本研究で最終目標としていたX線マイクロカロリメータによる環境放射線の計測までは到らなかったものの、小型断熱消磁冷凍機を用いたX線マイクロカロリメータ動作の環境を整えて、実現にめどをつけることができた。研究課題/領域番号:20651012, 研究期間(年度):2008 – 2010出典：研究課題「宇宙X線観測用精密分光器を応用した可搬型の微量環境放射線計測装置の試作」課題番号20651012（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-20651012/）を加工して作

A Case of Ovarian Actinomycosis

Background: Pelvic actinomycosis is uncommon and often presents as a complication of an intrauterine device (IUD). A diagnosis of actinomycosis can be made from the finding of sulfur granules within inflammatory exudate on histologic examination after surgery. However, it may be possible to diagnose actinomycosis before surgery by finding Actinomyces-like organisms on Papanicolaou smears. Case: A 41-year-old woman had been diagnosed as having a pelvic abscess, and bilateral salpingo-oophorectomy was performed. She had been an IUD user for 6 years. Actinomyces-like organisms were detected in her previous Papanicolaou cervical smears. If the patient had been treated when the Actinomyces-like organisms were detected by Papanicolaou smears, the serious ovarian actinomycosis might have been avoided. Conclusion: We suggest that routine cervical examinations are important for women who are IUD users

P-Process Nucleosynthesis inside Supernova-Driven Supercritical Accretion Disks

We investigate p-process nucleosynthesis in a supercritical accretion disk around a compact object of 1.4 M_solar, using the self-similar solution of an optically thick advection dominated flow. Supercritical accretion is expected to occur in a supernova with fallback material accreting onto a new-born compact object. It is found that appreciable amounts of p-nuclei are synthesized via the p-process in supernova-driven supercritical accretion disks (SSADs) when the accretion rate m_dot = M_dot c^2/(16 L_Edd) >10^5, where L_Edd is the Eddington luminosity. Abundance profiles of p-nuclei ejected from SSADs have similar feature to those of the oxygen/neon layers in Type II supernovae when the abundance of the fallback gas far from the compact object is that of the oxygen/neon layers in the progenitor. The overall abundance profile is in agreement with that of the solar system. Some p-nuclei, such as Mo, Ru, Sn, and La, are underproduced in the SSADs as in Type II supernovae. If the fallback gas is mixed with a small fraction of proton through Rayleigh-Taylor instability during the explosion, significant amounts of Mo92 are produced inside the SSADs. Ru96 and La138 are also produced when the fallback gas contains abundant proton though the overall abundance profile of p-nuclei is rather different from that of the solar system. The p-process nucleosynthesis in SSADs contributes to chemical evolution of p-nuclei, in particular Mo92, if several percents of fallback matter are ejected via jets and/or winds.Comment: 15 pages, 7 figures included, 3 tables, LaTeX emulateapj5.sty, accepted for publication by the Astronomical Journal (March, 2003

Search for a stochastic background of 100-MHz gravitational waves with laser interferometers

This letter reports the results of a search for a stochastic background of gravitational waves (GW) at 100 MHz by laser interferometry. We have developed a GW detector, which is a pair of 75-cm baseline synchronous recycling (resonant recycling) interferometers. Each interferometer has a strain sensitivity of ~ 10^{-16} Hz^{-1/2} at 100 MHz. By cross-correlating the outputs of the two interferometers within 1000 seconds, we found h_{100}^2 Omega_{gw} < 6 times 10^{25} to be an upper limit on the energy density spectrum of the GW background in a 2-kHz bandwidth around 100 MHz, where a flat spectrum is assumed.Comment: Accepted by Phys.Rev.Lett.; 10 pages, 4 figure