The variable iron K emission line in MCG-6-30-15

We report on the variability of the iron K emission line in the Seyfert 1 galaxy MCG--6-30-15 during a four-day ASCA observation. The line consists of a narrow core at an energy of about 6.4 keV, and a broad red wing extending to below 5 keV, which are interpreted as line emission arising from the inner parts of an accretion disk. The narrow core correlates well with the continuum flux whereas the broad wing weakly anti-correlates. When the source is brightest, the line is dominated by the narrow core, whilst during a deep minimum, the narrow core is very weak and a huge red tail appears. However, at other times when the continuum shows rather rapid changes, the broad wing is more variable than the narrow core, and shows evidence for correlated changes contrary to its long time scale behaviour. The peculiar line profile during the deep minimum spectrum suggests that the line emitting region is very close to a central spinning (Kerr) black hole where enormous gravitational effects operate.Comment: 13 pages, 13 ps figures, uses mn.sty (included) Accepted for publication in MNRA

COVID-19 vaccine effectiveness against severe COVID-19 requiring oxygen therapy, invasive mechanical ventilation, and death in Japan: A multicenter case-control study (MOTIVATE study).

INTRODUCTION: Since the SARS-CoV-2 Omicron variant became dominant, assessing COVID-19 vaccine effectiveness (VE) against severe disease using hospitalization as an outcome became more challenging due to incidental infections via admission screening and variable admission criteria, resulting in a wide range of estimates. To address this, the World Health Organization (WHO) guidance recommends the use of outcomes that are more specific to severe pneumonia such as oxygen use and mechanical ventilation. METHODS: A case-control study was conducted in 24 hospitals in Japan for the Delta-dominant period (August-November 2021; "Delta") and early Omicron (BA.1/BA.2)-dominant period (January-June 2022; "Omicron"). Detailed chart review/interviews were conducted in January-May 2023. VE was measured using various outcomes including disease requiring oxygen therapy, disease requiring invasive mechanical ventilation (IMV), death, outcome restricting to "true" severe COVID-19 (where oxygen requirement is due to COVID-19 rather than another condition(s)), and progression from oxygen use to IMV or death among COVID-19 patients. RESULTS: The analysis included 2125 individuals with respiratory failure (1608 cases [75.7%]; 99.2% of vaccinees received mRNA vaccines). During Delta, 2 doses provided high protection for up to 6 months (oxygen requirement: 95.2% [95% CI:88.7-98.0%] [restricted to "true" severe COVID-19: 95.5% {89.3-98.1%}]; IMV: 99.6% [97.3-99.9%]; fatal: 98.6% [92.3-99.7%]). During Omicron, 3 doses provided high protection for up to 6 months (oxygen requirement: 85.5% [68.8-93.3%] ["true" severe COVID-19: 88.1% {73.6-94.7%}]; IMV: 97.9% [85.9-99.7%]; fatal: 99.6% [95.2-99.97]). There was a trend towards higher VE for more severe and specific outcomes. CONCLUSION: Multiple outcomes pointed towards high protection of 2 doses during Delta and 3 doses during Omicron. These results demonstrate the importance of using severe and specific outcomes to accurately measure VE against severe COVID-19, as recommended in WHO guidance in settings of intense transmission as seen during Omicron

Discovery of a new X-ray transient source in the scutum region with Suzaku

During an observation of the Galactic plane in the Scutum region with the Suzaku satellite, we discovered a new X-ray transient source, designated Suzaku J1844-0404. Compared with previous Chandra observations of the same field, four Chandra X-ray sources exist within the current positional uncertainty of Suzaku J1844-0404. A firm identification is not possible. From the beginning of the observation, the X-ray intensity was significant at ∼ 5×10-14 erg s-1 cm-2 (2–10 keV), which may be a possible precursor. Later, the source exhibited a flare with a peak flux of ∼ 10-12 erg s-1 cm-2 (2–10 keV). A strong and narrow emission line at ∼ 6.66 keV was observed during the flare, most likely the He-like Fe line. The spectrum in 1–10 keV is consistent with a heavily absorbed (NH ∼3×1022Hcm-2) thin thermal emission with kT as high as ∼7keV. A single short flare, as observed, is rather unlikely for a cataclysmic variable. The source is probably an active binary star or a young stellar object

Solution-processed silicon films and transistors

Solution processes for electronic devices, instead of conventional vacuum process and vapour deposition, have been receiving considerable attention for a wide range of applications such as electroluminescent displays^, solar cells^3, ferroelectric films^4, transparent conductive films^5, SiO_2 films^6 and metal films^7, to reduce the processing cost. In particular, printing semiconductor devices using liquid materials is considered to be important for new applications, such as large-area flexible displays. Recent research has been focused on organic semiconductors^, which have mobilities comparable to that of amorphous silicon (α-Si)^11, but are insufficiently reliable. Solution processing of metal chalcogenide semiconductors to fabricate stable and high-performance transistors has also been reported^. This class of materials is targeted as substitutions for the silicon devices that requiree complex and expensive manufacturing processes. However, if high-quality silicon film could be prepared by solution process, this situation would change drastically. Here we demonstrate the solution process of silicon thin film transistors (TFTs) using a novel liquid precursor. We have formed poly-crystalline silicon (poly-Si) films by spin-coating or by ink-jetting the precursor to fabricate TFTs that operated with a mobilities of 108 cm^2V^s^ and 6.5 cm^2V^s^, respectively. These values cannot be achieved by solution-processed organic TFTs or α-Si TFTs, whose mobility is 1 cm^2V^s^ at most