On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40 − 8 + 8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M ⊙ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 Mpc ) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

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Abstract We report on multi-wavelength monitoring observations of an M-dwarf flare star AD Leonis with the Seimei Telescope (6150–7930 Å), SCAT (Spectroscopic Chuo-university Astronomical Telescope; 3700–7500 Å), and NICER (Neutron Star Interior Composition Explorer; 0.2–12.0 keV), with the collaboration of the OISTER (Optical and Infrared Synergetic Telescopes for Education and Research) program. Twelve flares are detected in total, including ten Hα, four X-ray, and four optical-continuum flares; one of them is a superflare with a total energy of ∼2.0 × 1033 erg. We found that: (1) during the superflare, the Hα emission line full width at 1/8 maximum dramatically increases to 14 Å from 8 Å in the low-resolution spectra (R ∼ 2000) accompanied by large white-light flares, (2) some weak Hα/X-ray flares are not accompanied by white-light emissions, and (3) the non-flaring emissions show clear rotational modulations in X-ray and Hα intensity in the same phase. To understand these observational features, one-dimensional hydrodynamic flare simulations are performed using the RADYN code. We find the simulated Hα line profiles with hard and high-energy non-thermal electron beams to be consistent with the initial phase line profiles of the superflares, while those with a softer and/or weak-energy beam are consistent with those in decay phases, indicating the changes in the energy fluxes injected to the lower atmosphere. Also, we find that the relation between the optical continuum and Hα intensity is nonlinear, which can be one cause of the non-white-light flares. The flare energy budget exhibits diversity in the observations and models, and more observations of stellar flares are necessary for constraining the occurrence of various emission line phenomena in stellar flares.

n-Type BaSi 2 epitaxial films with 900 nm thickness were grown on Si(111) by molecular beam epitaxy, and striped Au electrodes were formed on the surface. Photocurrents were clearly observed for photons with energies greater than 1.25 eV under bias voltages applied between the electrodes, and this increased sharply with increasing photon energy to attain a maximum at approximately 1.70 eV. The external quantum efficiency increased with the bias voltage and reached approximately 7% at 1.70 eV for a bias voltage of 7 V. This value is 100 times larger than the highest value ever reported for semiconducting silicide films. #

The layered transition metal oxide HNbMoO 6 is demonstrated to catalyze the esterification of lactic acid (a hydroxycarboxylic acid) with activity superior or comparable to conventional ion-exchange resins. Layered HNbMoO 6 also catalyzes the esterification of propionic acid (a carboxylic acid) in the presence of lactic acid, despite exhibiting negligible activity for any carboxylic acid as the sole reactant. X-ray diffraction (XRD) measurements indicate that lactic acid is intercalated into the interlayer structure of the oxide whereas carboxylic acid is not. The intercalation mechanism thus greatly affects the catalytic activity of this layered catalyst.

Polycrystalline BaSi2 layers with 300 nm thickness were grown by molecular beam epitaxy on (111)-oriented 100-nm-thick polycrystalline Si layers fabricated by an aluminum-induced crystallization method on SiO2. Photocurrents were clearly observed for photons with energies greater than 1.25 eV when bias voltage was applied between the 1.5-mm-spacing striped Al electrodes formed on the surface. The photoresponsivity increased sharply with increasing photon energy, attaining a maximum at approximately 1.60 eV. The external quantum efficiency increased with the bias voltage and reached approximately 8% at 5 V. This value is larger than that obtained for BaSi2 epitaxial films on Si(111).

n þ -BaSi 2 /p þ -Si tunnel junctions with different BaSi 2 template layer thicknesses were grown by molecular beam epitaxy. The template was found to be indispensable for growing epitaxial n þ -BaSi 2 , but the resistance of the junctions increased with template thickness. However, both epitaxial growth and low resistance were achieved for a template thickness of 1 nm. A current density of 21.9 A/cm 2 was achieved at 0.5 V. The photoresponsivity of 360-nm-thick undoped BaSi 2 grown on the tunnel junction increased with bias voltage and reached 74 mA/W at 2.3 eV under a reverse bias of 4 V, the highest value ever reported for semiconducting silicides. #

To identify the possible mechanism of coercivity (H c ) degradation of Nd-Fe-B sintered magnets, we study the roles of the exchange field acting on the 4f electrons in Nd ions and theoretically investigate how the variation of the exchange field affects the values of the magnetic anisotropy constants K 1 and K 2 . We find that, with decreasing exchange field strength, both values decrease as a result of the lower asphericity of the 4f electron cloud, indicating that the local anisotropy constants might become small around the grain boundaries where the exchange fields are decreased owing to the smaller coordination number.Nd-Fe-B sintered magnets [1][2][3] have the largest maximum energy product among the current magnets and have been widely used for magnetic devices such as voice coil motors in magnetic recording systems. Recently, because of the rapidly growing interest in electric vehicles, much effort has been made to suppress the degradation of the coercivity (H c ) of Nd-Fe-B magnets. However, from an industrial viewpoint, reduction in the usage of Dy is strongly desired, because Dy is a rare metal and the magnetization of the Nd-Fe-B magnets decreases by substituting Dy with Nd owing to the antiparallel coupling between Dy and Fe moments. Realizing Dy-free high-performance Nd-Fe-B magnets requires a further increase of H c in the Nd-Fe-B system by microstructure optimization, [4][5][6][7][8][9][10][11] and therefore, establishing the microscopic foundation for the coercivity mechanism is desired. From a theoretical viewpoint, many works [12][13][14][15][16] have focused on the change of magnetic anisotropy constants around the grain boundary surfaces as a result of the stresses, defects, and change of spatial symmetry. In addition, micromagnetic model calculations have shown that the surface c-plane anisotropy can drastically decrease the coercivity. 17) For these reasons, evaluation of the local anisotropy constants around the grain boundaries and determining their temperature dependence are important to investigate the degradation of the coercivity.With regard to the magnetic anisotropy of rare earth (RE) transition metal compounds, it is believed that the 4f electrons in RE ions are responsible for the main part of the magnetic anisotropy and that the crystalline electric field (CEF) acting on the 4f electrons dominates this property. 18) Under the assumption that the exchange field on the 4f electrons is strong enough, by using the CEF parameter A 0 2 , the leading anisotropy constant K 1 can be approximately described by K 1 = −3J(J −1)α r 2 A 0 2 N R , where α is the Stevens factor, J is the total angular momentum, r 2 is the average ofr 2 over the radial wave function of the 4f electrons, and N R is the density of RE ions. Note that the CEF parameter