An extensive study on the potassium abundances of late-type stars was carried out by applying the non-LTE spectrum-fitting analysis to the K I resonance line at 7698.96 Å to a large sample of 160 FGK dwarfs and 328 late-G /early-K giants (including 89 giants in the Kepler field with seismologically known ages) belonging to the disk population (−1 ≤ [Fe/H] ≤ 0.5), which may provide important observational constraint on the nucleosynthesis history of K in the galactic disk. Special attention was paid to clarifying the observed behaviors of [K/Fe] in terms of [Fe/H] along with stellar age, and to checking whether giants and dwarfs yield consistent results with each other. The following results were obtained. (1) A slightly increasing tendency of [K/Fe] with a decrease in [Fe/H] (d[K/Fe]/d[Fe/H] 〜 −0.1 to −0.15; a shallower slope than reported by previous studies) was confirmed for FGK dwarfs, though thick-disk stars tend to show larger [K/Fe] deviating from this gradient. (2) Almost similar characteristics were observed also for apparently bright field giants locating in the solar neighborhood (such as dwarfs). (3) However, the [K/Fe] vs. [Fe/H] relation for more distant Kepler giants shows larger scatter and is systematically higher (by ≤ 0.1 dex) than that of dwarfs, implying that chemical evolution of K is rather diversified depending on the position in the Galaxy. (4) Regarding the age-dependence, a marginal trend of increasing [K/Fe] with age is recognized for dwarfs, while any systematic tendency is not observed for Kepler giants. These consequences may suggest that evolution of [K/Fe] with time in the galactic disk does exist but proceeded more gradually than previously thought, and its condition is appreciably location-dependent.

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If abundance difference between the primary and secondary star indicates the chemical distribution in the molecular cloud, some visual binaries have abundance differences between the stellar components. The previous work showed the weak correlation between the abundance difference and the binary separation. This work regards the difference between the equivalent widths of the primary star and secondary star as the abundance difference because the atmospheric parameters of the stellar components are almost the same in the equal mass binaries. Therefore, we measured the equivalent widths of the Fe I absorption lines of the stellar components in the visual binaries, and investigated whether the difference of both equivalent widths determines the abundance difference between the primary and secondary stars. For 16 Cyg AB, 83 Leo AB, HD 80606/80607 and XO-2 NS, the difference of both equivalent width (A-B) is -0.0042±0.0040 Å, -0.0040±0.0099 Å, 0.0001±0.0031 Å, and 0.0156±0.0067 Å, respectively. These results are consistent with ones in the previous works.

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The author hereby presents the evaluated performance of the NIC polarimetry mode, which was re-developed in 2018. Imaging polarimetric observations were conducted for strongly polarized standard stars with their polarization degrees of 〜0.4%—6 % in the J band. The accuracy of the polarimetry in terms of the polarization degrees and position angles was evaluated based on a comparison between measured values and those found in the literature. The systematic bias in polarization degrees was found to be within 0.3%, though some depolarization in the instrument was suspected. No significant systematic bias in polarization position angles was detected for the precision of a few degrees. In addition, for use in planning observations, a relationship was established between the random error in the polarization degrees and the total integration time.

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We spectroscopically observed a solar active region NOAA12709 on the Domeless Solar Telescope at Hida Observatory of Kyoto University. We could detect several spicules in our data which show jet-like dynamic features. Using the acquired spectral data, physical quantities such as the time change of Doppler velocities and optical thicknesses at the tips of the spicules were derived from the cloud model. As a result, a positive correlation was found among the maximum length, height and the maximum speed. This could be obtained by a jet-like model that the spicules were generated by a rapid increase in pressure at low altitude. The lifetime of the spicules near the active region was shorter than that of the quiet region, and the spiclues developed or declined while changing the inclination angle. Clear interpretation of the optical thickness increase will require further analysis to detect internal structure of flow field of spicules which are grown along the curve.

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Optical multi-band photometric observations of SX Phe-type object BL Cam were carried out with 60-cm reflect-ing telescope equipped with CCD camera in 2016 November and 2018 January. The color index B-V is estimated as 0.35 from the obtained B- and V-band data. The surface temperature is estimated 6680 K based on this color index. The variations of radius accompanying the variations of luminosity were detected, however, the variations do not correspond to that ever observed in similar objects. The maximum of stellar radius variation is delayed by 0.3〜0.4 of phase to the maximum of light curve variation.

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This study investigates radial age profiles of local barred and unbarred galaxies using Mapping Nearby Galaxies at APO (MaNGA) survey data. Galaxies with prominent bars were selected from the Galaxy Zoo catalogue as a barred sample, and those without bars as a control sample. These samples were divided into three stellar-mass bins, log M/Msun = 10.0-10.5, 10.5-11.0, and 11.0-11.5, respectively. The numbers of galaxies in each bin were 5, 24, and 19 for the barred sample, and 25, 48, and 38 for the mass-matched control sample, respectively. The luminosity-weighted age profiles of barred galaxies were flat at central 3 kpc regions and were 0.2-0.4 dex higher than the control sample at outer regions. This indicates bar-induced star-formation in the central regions and bar-quenching in the outer regions. On the other hand, the mass-weighted age profiles of both samples monotonically increased towards the central regions. This suggests that barred galaxies also follow inside-out quenching, regardless of bar-induced central star-formation and/or bar-quenching of disk regions.

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We examined the time evolution and the environmental effects on properties of 32,200 nearby galaxies in the redshift range 0.025< z < 0.1 extracted from the public SDSS data release 14 database. The galaxies are categorized into four groups, isolated galaxy, high-density galaxy, low-density galaxy, and others in the viewpoints of distance from the neighboring galaxy and local galaxy number density. We also found analogous effects to the Butcher-Oemler effect and the morphological Butcher-Oemler effect also in the low galaxy density region not only in the high density region. However, the correlation is weak in the low density region. Dependences of color and morphology on the logarithmic galaxy number density showed almost linear decrease over 3-orders of density change. On the other hand, color- and morphology-r5, distance to the fifth nearest neighbor, plots suggested three characteristic density regions. At r5 > 7 Mpc, the environmental effect is evident, whereas it is not so effective at r5 <12 Mpc. There is an intermediate region between these two regions. We also analyzed color and morphology of the galaxies in the two-dimensional time (redshift)-environment (density) space. Both properties are governed by the combination of the two variables, redshift and density. We may say one order density difference is equivalent to 0.6-0.8 Gyr-delay in time evolution.

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