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We report a possible detection of a 55-day X-ray modulation for the ultraluminous accreting pulsar M82 X-2 from archival Chandra observations. Because M82 X-2 is known to have a 2.5-day orbital period, if the 55-day period is real, it will be the superorbital period of the system. We also investigated variabilities of other three nearby ultraluminous X-ray sources in the central region of M82 with the Chandra data and did not find any evidence of periodicities. Furthermore, we re-examined the previously reported 62-day periodicity near the central region of M82 by performing a systematic timing study with all the archival Rossi X-Ray Timing Explorer and Swift data. Using various dynamic timing analysis methods, we confirmed that the 62-day period is not stable, suggesting that it is not the orbital period of M82 X-1 in agreement with previous work.

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For the applications involving ambient light sensing, the spectral response of photodetectors is required to mimic that of human eyes and the cost must be low. This paper discusses the layer structure design of human-eye-like hydrogenated amorphous silicon (a-Si:H) p-i-n photodiodes. The resultant sample devices are insensitive to infrared light and have a normal spectral response in the light band ranging between 400 nm wavelength and 740 nm wavelength. The spectrum peak locates around 560 nm wavelength, similar to the case of human eyes. The devices are suitable for low-cost ambient light sensing applications