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High polarization degree of the continuum of comet 2P/Encke based on spectropolarimetric signals during its 2017 apparition

Kwon, Y. G.,Ishiguro, M.,Shinnaka, Y.,Nakaoka, T.,Kuroda, D.,Hanayama, H.,Takahashi, J.,Baar, S.,Saito, T.,Kawabata, M.,Uemura, M.,Morokuma, T.,Murata, K. L.,Takagi, S.,Morihana, K.,Nagayama, T.,Sekig Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-
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Context. Spectropolarimetry is a powerful technique for investigating the physical properties of gas and solid materials in cometary comae without mutual contamination, but only a few spectropolarimetric studies have been conducted to extract each component.Aims. We attempt to derive the continuum (i.e., scattered light from dust coma) polarization degree of comet 2P/Encke, free of the influence of molecular emissions. The target is unique in that its orbit is dynamically decoupled from Jupiter, like the main-belt asteroids, but it ejects gas and dust like ordinary comets.Methods. We observed the comet using the Hiroshima Optical and Near-Infrared Camera attached to the Cassegrain focus of the 150 cm Kanata telescope on UT 2017 February 21 when the comet was at the solar phase angle of α = 75°.7.Results. We find that the continuum polarization degree with respect to the scattering plane is Pcont, r = 33.8 ± 2.7% at the effective wavelength of 0.82 μm, which is significantly higher than those of cometary dust in a high-Pmax group at similar phase angles. Assuming that an ensemble polarimetric response of the dust of 2P/Encke as a function of phase angle is morphologically similar with those of other comets, its maximum polarization degree is estimated to Pmax ≳ 40% at αmax ≈ 100°. In addition, we obtain the polarization degrees of the C2 swan bands (0.51-0.56 μm), the NH2α bands (0.62-0.69 μm), and the CN-red system (0.78-0.94 μm) in a range of 3-19%, which depend on the molecular species and rotational quantum numbers of each branch. The polarization vector is aligned nearly perpendicularly to the scattering plane with an average of 0°.4 over a wavelength range of 0.50-0.97 μm.Conclusions. From the observational evidence, we conjecture that the high polarization degree of 2P/Encke might be attributable to a dominance of large dust particles around the nucleus, which have remained after frequent perihelion passages near the Sun.
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CONSTRAINING SUPERNOVA PROGENITORS: AN INTEGRAL FIELD SPECTROSCOPIC SURVEY OF THE EXPLOSION SITES

KUNCARAYAKTI, H.,ALDERING, G.,ANDERSON, J.P.,ARIMOTO, N.,DOI, M.,GALBANY, L.,HAMUY, M.,HASHIBA, Y.,KRUEHLER, T.,MAEDA, K.,MOROKUMA, T.,USUDA, T. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
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  ScienceON
  
  코리아스칼라
We describe a survey of nearby core-collapse supernova (SN) explosion sites using integral field spectroscopy (IFS) techniques, which is an extension of the work described in Kuncarayakti et al. (2013). The project aims to constrain SN progenitor properties based on the study of the immediate environment of the SN. The stellar populations present at the SN explosion sites are studied by means of integral field spectroscopy, which enables the acquisition of both spatial and spectral information of the object simultaneously. The spectrum of the SN parent stellar population gives an estimate of its age and metallicity. With this information, the initial mass and metallicity of the once coeval SN progenitor star are derived. While the survey is mostly done in optical, the additional utilization of near-infrared integral field spectroscopy assisted with adaptive optics (AO) enables us to examine the explosion sites in high spatial detail, down to a few parsecs. This work is being carried out using multiple 2-8 m class telescopes equipped with integral field spectrographs in Chile and Hawaii.