Abstract
The Subaru telescope is currently performing a strategic program (SSP) using the high-precision near-infrared (NIR) spectrometer IRD to search for exoplanets around nearby mid/late M dwarfs ...via radial velocity (RV) monitoring. As part of the observing strategy for the exoplanet survey, signatures of massive companions such as RV trends are used to reduce the priority of those stars. However, this RV information remains useful for studying the stellar multiplicity of nearby M dwarfs. To search for companions around such “deprioritized” M dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2 with pyramid wave-front sensing at NIR wavelengths, leading to high sensitivity to substellar-mass companions within a few arcseconds. We detected two new companions (LSPM J1002+1459 B and LSPM J2204+1505 B) and two new candidates that are likely companions (LSPM J0825+6902 B and LSPM J1645+0444 B), as well as one known companion. Including two known companions resolved by the IRD fiber injection module camera, we detected seven (four new) companions at projected separations between ∼2 and 20 au in total. A comparison of the colors with the spectral library suggests that LSPM J2204+1505 B and LSPM J0825+6902 B are located at the boundary between late M and early L spectral types. Our deep high-contrast imaging for targets where no bright companions were resolved did not reveal any additional companion candidates. The NIRC2 detection limits could constrain potential substellar-mass companions (∼10–75
M
Jup
) at 10 au or further. The failure with Keck/NIRC2 around the IRD-SSP stars having significant RV trends makes these objects promising targets for further RV monitoring or deeper imaging with the James Webb Space Telescope to search for smaller-mass companions below the NIRC2 detection limits.
We succeeded in developing a broadband-frequency-variable laser comb with a mode spacing of 12.5 GHz in the near-infrared region. We found that the spectrum of optical pump pulses can be frequency ...shifted over the mode spacing frequency by a single-sideband (SSB) optical modulator involving the amplitude and phase. Optical heterodyne measurement showed that the frequency shift of the optical pump pulses was precisely consistent with the modulation frequency applied to the SSB modulator with an accuracy of 20 kHz. The pump pulses were amplified and compressed to enhance the peak intensity. Finally, the frequency-shifted pump pulses launched into highly nonlinear fibers and generated a frequency-shifted laser comb. The precise frequency shift of pump pulses induced a simultaneous frequency shift of all modes of the laser comb. As a result, we succeeded in fast frequency sweeping of the laser comb over a full spectral range of 1080 to 1750 nm. This full-wavelength tuning implies that laser light of arbitrary and accurate wavelength can be obtained over the comb bandwidth.
Multivariate public-key cryptosystems are potential candidates for post-quantum cryptography. The security of multivariate public-key cryptosystems relies on the hardness of solving a system of ...multivariate quadratic polynomial equations. Faugère’s F4 algorithm is one of the solution techniques based on the theory of Gröbner bases and selects critical pairs to compose the Macaulay matrix. Reducing the matrix size is essential. Previous research has not fully examined how many critical pairs it takes to reduce to zero when echelonizing the Macaulay matrix in rows. Ito et al. (2021) proposed a new critical-pair selection strategy for solving multivariate quadratic problems associated with encryption schemes. Instead, this paper extends their selection strategy for solving the problems associated with digital signature schemes. Using the OpenF4 library, we compare the software performance between the integrated F4-style algorithm of the proposed methods and the original F4-style algorithm. Our experimental results demonstrate that the proposed methods can reduce the processing time of the F4-style algorithm by up to a factor of about seven under certain specific parameters. Moreover, we compute the minimum number of critical pairs to reduce to zero and propose their extrapolation outside our experimental scope for further research.
A left ventricular assist device (LVAD) is a treatment option for patients with end-stage heart failure; however, a certain number of patients on durable LVADs are diagnosed with malignancy. ...Radiation therapy (RT) for patients with durable LVADs has safety concerns, because RT may interfere with the device. Herein, we report a case of RT during durable LVAD management. A 48-year-old man with a durable LVAD was diagnosed with sinusitis. As his symptoms were resistant to drug therapy, endoscopic sinus surgery was performed, and extranodal NK/T-cell lymphoma, nasal type (ENKL) was pathologically detected. Since RT was the first-line treatment for ENKL, we conducted two types of irradiation experiments to determine whether RT can be safely performed in patients with durable LVADs as follows: (1) assessing the extent of the radiation levels at each site and evaluating device malfunction by irradiating the lesion sites in the patient model with the same protocol as planned, and (2) evaluating device malfunction by directly irradiating the durable LVAD equipment once at the scheduled total dose. The radiation doses at the pump, driveline, system controller, power cable, and power module of the durable LVAD reached 7.86 cGy, 6.34 cGy, 0.66 cGy, 0.38 cGy, and 0.14 cGy, respectively. In both experiments, durable LVAD malfunction or any type of alarm was not observed. We concluded that RT could be safely performed with chemotherapy in this patient and our irradiation experiments can be applied to RT for other malignancies.
In this study, we introduced an optical pulse synthesizer (OPS) to measure frequency chirps of optical pulses by differential processing. The OPS has a single-chip integrated structure of all ...elements for the differential filtering and enables stable measurement. Because the exact filter causes a large loss, we employed a phase-only filter, whose frequency response was only in phase. We measured chirp rates of pulses which were induced by propagating standard single mode fibers with different lengths. The retrieved chirp rates were comparable to calculated results. We simulated accuracy of the method and concluded that our experiment had phase control accuracy within ~0.07π.
•An optical pulse synthesizer is employed as a reconfigurable filter.•Frequency chirp of an optical pulse was measured by frequency differentiation.•The phase control accuracy of the filter was estimated by simulation.
Abstract
Silicon and strontium are key elements to explore the nucleosynthesis and chemical evolution of the Galaxy by measurements of very metal-poor stars. There are, however, only a few useful ...spectral lines of these elements in the optical range that are measurable for such low-metallicity stars. Here we report on abundances of these two elements determined from near-infrared high-resolution spectra obtained with the Subaru Telescope Infrared Doppler instrument. Si abundances are determined for as many as 26 Si lines for six very and extremely metal-poor stars (−4.0 < Fe/H < −1.5), which significantly improves the reliability of the abundance measurements. All six stars, including three carbon-enhanced objects, show over-abundances of Si (Si/Fe ∼ +0.5). Two stars with Fe/H ∼ −1.5 have relatively small over-abundances. The Mg/Si ratios agree with the solar value, except for one metal-poor star with carbon excess. Strontium abundances are determined from the triplet lines for four stars, including two for the first time. The consistency of the Sr abundances determined from near-infrared and optical spectra require further examination from additional observations.
We demonstrate a method of background component suppression of synthesized pulses for flatly broadened supercontinuum (SC) generation. An adaptive pulse shaping in frequency domain achieved a 26 dB ...contrast between pulse center and background level in auto-correlation trace by combining two fitness functions during feedback-controlled pulse shaping. The pulse was used as a SC pump, and the spectral peak of the SC at the pump wavelength was suppressed by 5 dB using the combination scheme. Simulation results show that the phase spectra control is required to be within ± π/100 rad to suppress the spectral peak below 3 dB. The results show that adaptive pulse shaping is required to improve SC flatness due to the small mismatch tolerance.
A multi-gigahertz frequency comb (MGFC)-based interferometer was developed for profilometry and tomography using a frequency variable supercontinuum (SC). The comparatively flattened and broadened SC ...light source with variable multi-gigahertz interval frequency was developed using an optical pulse synthesizer and highly nonlinear dispersion flattened fiber. The generated SC provided a stable interference output with a full width half maximum of 19 μm during interval frequency sweeping of over 400 MHz. We experimentally confirmed that the interference signal exhibited an envelope-only waveform without fringes, which enabled the drastic reduction of the sampling points resulting in high speed measurement. A full-field 3-D image with 320 × 256 × 300 pixels was acquired with a measurement time of only 10 seconds. It was demonstrated that the MGFC-based interferometer with the novel SC light source has the potential for application in a high speed full-field 3-D metrology.
N-Tosyl 3-substituted indoles were hydrogenated with high enantioselectivities (95−98% ee) by use of a trans-chelating chiral bisphosphine, (S,S)-(R,R)-PhTRAP ligand. The chiral catalyst, which was ...generated in situ from Rh(nbd)2SbF6, PhTRAP, and Cs2CO3, is useful for enantioselectively synthesizing a range of diverse optically active indolines possessing a chiral carbon at the 3-position.
We precisely generate dark solitons using an optical pulse synthesizer (OPS) at a repetition rate of 25 GHz and experimentally investigate soliton transmission through a normal-dispersion fiber. ...Because of their particular waveform, there are not many experimental studies. The OPS provides frequency-domain line-by-line modulation and produces arbitrary pulse waveforms. The soliton waveform has an intensity contrast greater than 20 dB. At certain input peak power, the pulse exhibits soliton transmission and maintains its initial waveform. The power agrees with soliton transmission theory. We confirm that the π phase shift at the center of the dark soliton is maintained after transmission through the fiber. We also investigate the influence of stimulated Brillouin scattering for long-distance transmission.
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