Masayuki Yamanaka

Early Phase Obserbations of Extermely Luminous Type Ia Supernova 2009dc

We present early phase observations in optical and near-infrared wavelengths for the extremely luminous Type Ia supernova (SN Ia) 2009dc. The decline rate of the light curve is ?m 15(B) = 0.65 ? 0.03, which is one of the slowest among SNe Ia. The peak V-band absolute magnitude is estimated to be MV = ?19.90 ? 0.15?mag if no host extinction is assumed. It reaches MV = ?20.19 ? 0.19?mag if we assume the host extinction of AV = 0.29?mag. SN 2009dc belongs to the most luminous class of SNe Ia, like SNe 2003fg and 2006gz. Our JHKs -band photometry shows that this SN is also one of the most luminous SNe Ia in near-infrared wavelengths. We estimate the ejected 56Ni mass of 1.2 ? 0.3 M ? for the no host extinction case (and of 1.6 ? 0.4 M ? for the host extinction of AV = 0.29?mag). The C II ?6580 absorption line remains visible until a week after the maximum brightness, in contrast to its early disappearance in SN 2006gz. The line velocity of Si II ?6355 is about 8000?km?s?1 around the maximum, being considerably slower than that of SN 2006gz. The velocity of the C II line is similar to or slightly less than that of the Si II line around the maximum. The presence of the carbon line suggests that the thick unburned C+O layer remains after the explosion. Spectropolarimetric observations by Tanaka et?al. indicate that the explosion is nearly spherical. These observational facts suggest that SN 2009dc is a super-Chandrasekhar mass SN Ia.

Nebular Phase Observations of the Type Ib Supernova 2008D/X-Ray Transient 080109 : Side-Viewed Bipolar Explosion

We present optical spectroscopic and photometric observations of supernova (SN) 2008D, associated with the luminous X-ray transient 080109, at >300 days after the explosion (nebular phases). We also give flux measurements of emission lines from the H II region at the site of the SN, and estimates of the local metallicity. The brightness of the SN at nebular phases is consistent with the prediction of the explosion models with an ejected {sup 56}Ni mass of 0.07 M{sub sun}, which explains the light curve at early phases. The [O I] line in the nebular spectrum shows a double-peaked profile while the [Ca II] line does not. The double-peaked [O I] profile strongly indicates that SN 2008D is an aspherical explosion. The profile can be explained by a torus-like distribution of oxygen viewed from near the plane of the torus. We suggest that SN 2008D is a side-viewed, bipolar explosion with a viewing angle of >50 deg. from the polar direction.

Extremely Luminous Supernova 2006gy at Late Phase: Detection of Optical Emission from Supernova

Supernova (SN) 2006gy is an extremely luminous Type IIn SN characterized by the bright peak magnitude MR ~?22?mag and its long duration. The mechanism giving rise to its huge luminosity is still unclear. We performed optical spectroscopy and photometry of SN 2006gy at late time, ~400 days after the explosion, with the Subaru/FOCAS in a good seeing condition. We carefully extracted the SN component, although there is an ambiguity because of the contamination by bright nucleus of the host galaxy. We found that the SN faded by ~3?mag from ~200 to ~400 days after the explosion (i.e., by ~5?mag from peak to ~400 days) in R band. The overall light curve is marginally consistent with the 56Ni heating model, although the flattening around 200 days suggests the optical flux declined more steeply between ~200 and ~400 days. The late time spectrum was quite peculiar among all types of SNe. It showed many intermediate width (~2000 km s?1 FWHM) emission lines, e.g., [Fe II], [Ca II], and Ca II. The absence of the broad [O I] 6300, 6364 line and weakness of [Fe II] and [Ca II] lines compared with Ca II IR triplet would be explained by a moderately high electron density in the line emitting region. This high-density assumption seems to be consistent with the large amount of ejecta and low expansion velocity of SN 2006gy. The H? line luminosity was as small as ~1? 1039 erg s?1, being comparable with those of normal Type II SNe at similar epochs. Our observation indicates that the strong circumstellar medium interaction had almost finished by ~400 days. If the late time optical flux is purely powered by radioactive decay, at least M(56Ni) ~ 3 M ? should be produced at the SN explosion. In the late phase spectrum, there were several unusual emission lines at 7400??-8800?? and some of them might be due to Ti or Ni synthesized at the explosion.

OPTICAL AND NEAR-INFRARED POLARIMETRY OF HIGHLY REDDENED Type Ia SUPERNOVA 2014J: PECULIAR PROPERTIES OF DUST IN M82

We presented optical and near-infrared multi-band linear polarimetry of the highly reddened Type Ia SN~2014J appeared in M82. SN~2014J exhibits large polarization at shorter wavelengths, e.g.,

TYPE IIb SUPERNOVA 2013df ENTERING INTO AN INTERACTION PHASE: A LINK BETWEEN THE PROGENITOR AND THE MASS LOSS

4.8

Three-Dimensional Explosion Geometry Of Stripped-Envelope Core-Collapse Supernovae. I. Spectropolarimetric Observations

\% in

Bayesian Approach to Find a Long-Term Trend in Erratic Polarization Variations Observed in Blazars

B

PROPERTIES OF NEWLY FORMED DUST GRAINS IN THE LUMINOUS TYPE IIn SUPERNOVA 2010jl

band, and the polarization decreases rapidly at longer wavelengths, with the position angle of the polarization remaining at approximately

Early Spectral Evolution of the Rapidly Expanding Type Ia Supernova 2006X

40^{\circ}

Survey of period variations of superhumps in SU UMa-type dwarf novae. VI. The sixth year (2013-2014)

over the observed wavelength range. These polarimetric properties suggest that the observed polarization is likely to be caused predominantly by the interstellar dust within M82. Further analysis shows that the polarization peaks at a wavelengths much shorter than those obtained for the Galactic dust. The wavelength dependence of the polarization can be better described by an inverse power law rather than by Serkowski law for Galactic interstellar polarization. These suggests that the nature of the dust in M82 may be different from that in our Galaxy, with polarizing dust grains having a mean radius of