K. Kawabata - Academia.edu (original) (raw)

Papers by K. Kawabata

Monthly Notices of the Royal Astronomical Society, 2007

The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernov... more The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernova (SN Ic) 2003jd are presented. In total, 74 photometric data points and 26 spectra were collected using 11 different telescopes. SN 2003jd is one of the most luminous SN Ic ever observed. A comparison with other Type Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case between broad-line events (2002ap, 2006aj) and highly energetic SNe (1997ef, 1998bw, 2003dh, 2003lw), with an ejected mass of M ej = 3.0 ± 1 M and a kinetic energy of E k (tot) = 7 +3 −2 × 10 51 erg. SN 2003jd is similar to SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and 2002ap in terms of light-curve shape and spectral evolution. The comparison with other SNe Ic suggests that the V-band light curves of SNe Ic can be partially homogenized by introducing a time-stretch factor. Finally, because of the similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the possible connection of SN 2003jd with a gamma-ray burst (GRB).

The Astrophysical …, 2007

Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at... more Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at t 1 days after GRB 060218, the X-ray flash with which it was associated. Strong nebular emission lines with 200 an expansion velocity of km s were detected. The ...

We carried out spectro-polarimetry of three outburst objects, CI Cam, Nova Sgr 1998, and U Sco. A... more We carried out spectro-polarimetry of three outburst objects, CI Cam, Nova Sgr 1998, and U Sco. Although we were not able to detect the evidence of the intrinsic polarization for the former two stars, we succeeded in confirming the existence of intrinsic polarization for the last one, U Sco. U Sco showed de-polarization effect on emission lines. It also showed rapid variation of the continuum polarization. Its behavior resembles that observed for a classical nova, V1974 Cyg, although the time-scale of variation differs between two novae.

Astrophysical Journal, 2003

Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May u... more Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May using the Subaru 8.2 m telescope are presented. The properties of the SN are investigated through a comparison with spectra of the Type Ic hypernovae SNe 1997ef and 1998bw. (Hypernovae being a tentatively defined class of SNe with very broad absorption features: these features suggest a large velocity

Astrophysical Journal, 2003

The spectra of SN 2003dh, identified in the afterglow of GRB030329, are modeled using radiation t... more The spectra of SN 2003dh, identified in the afterglow of GRB030329, are modeled using radiation transport codes. It is shown that SN 2003dh had a high explosion kinetic energy ($\sim 4 \times 10^{52}$ erg in spherical symmetry), making it one of the most powerful hypernovae observed so far, and supporting the case for association between hypernovae and Gamma Ray Bursts. However, the light curve derived from fitting the spectra suggests that SN 2003dh was not as bright as SN 1998bw, ejecting only sim0.35Msun\sim 0.35\Msunsim0.35Msun of \Nifs. The spectra of SN 2003dh resemble those of SN 1998bw around maximum, but later they look more like those of the less energetic hypernova SN 1997ef. The spectra and the inferred light curve can be modeled adopting a density distribution similar to that used for SN 1998bw at $ v > 25,000$\kms but more like that of SN 1997ef at lower velocities. The mass of the ejecta is sim8Msun\sim 8\Msunsim8Msun, somewhat less than in the other two hypernovae. The progenitor must have been a ...

The Astrophysical …, 2002

We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis:... more We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis: the data were taken at two epochs, close to and one month later than the visual maximum (2002 February 8). In addition we present June 9 spectropolarimetry without analysis. The data show the development of linear polarization. Distinct polarization profiles were seen only in the O I λ7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the O I λ7773 multiplet and Ca II IR triplet absorption troughs a month later, with the latter showing a peak polarization as high as ∼ 2 %. The intrinsic polarization shows three clear position angles: 80 • for the February continuum, 120 • for the February line feature, and 150 • for the March data. We conclude that there are multiple asymmetric components in the ejecta. We suggest that the supernova has a bulk asymmetry with an axial ratio projected on the sky that is different from 1 by of order 10 %. Furthermore, we suggest very speculatively that a high velocity ejecta component moving faster than ∼ 0.115c (e.g., a jet) contributes to polarization in the February epoch.

The Astrophysical Journal, 2009

Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity h... more Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity have been discovered. Their luminosity requires more than 1 M ⊙ of 56 Ni ejected during the explosion, suggesting that they might have originated from super-Chandrasekhar mass white dwarfs. However, the nature of these objects is not yet well understood. In particular, no data have been taken at late phases, about one year after the explosion. We report on Subaru and Keck optical spectroscopic and photometric observations of the SN Ia 2006gz, which had been classified as being one of these "overluminous" SNe Ia. The late-time behavior is distinctly different from that of normal SNe Ia, reinforcing the argument that SN 2006gz belongs to a different subclass than normal SNe Ia. However, the peculiar features found at late times are not readily connected to a large amount of 56 Ni; the SN is faint, and it lacks [Fe II] and [Fe III] emission. If the bulk of the radioactive energy escapes the SN ejecta as visual light, as is the case in normal SNe Ia, the mass of 56 Ni does not exceed ∼ 0.3 M ⊙. We discuss several possibilities to remedy the problem. With the limited observations, however, we are unable to conclusively identify which process is responsible. An interesting possibility is that the bulk of the emission might be shifted to longer wavelengths, unlike the case in other SNe Ia, which might be related to dense C-rich regions as indicated by the early-phase data. Alternatively, it might be the case that SN 2006gz, though peculiar, was actually not substantially overluminous at early times. Subject headings: white dwarfs-radiative transfer-supernovae: individual (SN 2006gz) 1 Based on data collected at the Subaru Telescope (operated by the National Astronomical Observatory of Japan) and the W. M. Keck Observatory (operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; supported by the W. M. Keck Foundation).

Astronomy & Astrophysics, 2015

Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-su... more Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at ∼300 days after the explosion, and discuss these in the context of constraints on the supernova's progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lowermass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O I]/[Ca II] line ratio with other supernovae.

Monthly Notices of the Royal Astronomical Society, 2007

The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernov... more The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernova (SN Ic) 2003jd are presented. In total, 74 photometric data points and 26 spectra were collected using 11 different telescopes. SN 2003jd is one of the most luminous SN Ic ever observed. A comparison with other Type Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case between broad-line events (2002ap, 2006aj) and highly energetic SNe (1997ef, 1998bw, 2003dh, 2003lw), with an ejected mass of M ej = 3.0 ± 1 M and a kinetic energy of E k (tot) = 7 +3 −2 × 10 51 erg. SN 2003jd is similar to SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and 2002ap in terms of light-curve shape and spectral evolution. The comparison with other SNe Ic suggests that the V-band light curves of SNe Ic can be partially homogenized by introducing a time-stretch factor. Finally, because of the similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the possible connection of SN 2003jd with a gamma-ray burst (GRB).

The Astrophysical …, 2007

Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at... more Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at t 1 days after GRB 060218, the X-ray flash with which it was associated. Strong nebular emission lines with 200 an expansion velocity of km s were detected. The ...

We carried out spectro-polarimetry of three outburst objects, CI Cam, Nova Sgr 1998, and U Sco. A... more We carried out spectro-polarimetry of three outburst objects, CI Cam, Nova Sgr 1998, and U Sco. Although we were not able to detect the evidence of the intrinsic polarization for the former two stars, we succeeded in confirming the existence of intrinsic polarization for the last one, U Sco. U Sco showed de-polarization effect on emission lines. It also showed rapid variation of the continuum polarization. Its behavior resembles that observed for a classical nova, V1974 Cyg, although the time-scale of variation differs between two novae.

Astrophysical Journal, 2003

Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May u... more Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May using the Subaru 8.2 m telescope are presented. The properties of the SN are investigated through a comparison with spectra of the Type Ic hypernovae SNe 1997ef and 1998bw. (Hypernovae being a tentatively defined class of SNe with very broad absorption features: these features suggest a large velocity

Astrophysical Journal, 2003

The spectra of SN 2003dh, identified in the afterglow of GRB030329, are modeled using radiation t... more The spectra of SN 2003dh, identified in the afterglow of GRB030329, are modeled using radiation transport codes. It is shown that SN 2003dh had a high explosion kinetic energy ($\sim 4 \times 10^{52}$ erg in spherical symmetry), making it one of the most powerful hypernovae observed so far, and supporting the case for association between hypernovae and Gamma Ray Bursts. However, the light curve derived from fitting the spectra suggests that SN 2003dh was not as bright as SN 1998bw, ejecting only sim0.35Msun\sim 0.35\Msunsim0.35Msun of \Nifs. The spectra of SN 2003dh resemble those of SN 1998bw around maximum, but later they look more like those of the less energetic hypernova SN 1997ef. The spectra and the inferred light curve can be modeled adopting a density distribution similar to that used for SN 1998bw at $ v > 25,000$\kms but more like that of SN 1997ef at lower velocities. The mass of the ejecta is sim8Msun\sim 8\Msunsim8Msun, somewhat less than in the other two hypernovae. The progenitor must have been a ...

The Astrophysical …, 2002

We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis:... more We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis: the data were taken at two epochs, close to and one month later than the visual maximum (2002 February 8). In addition we present June 9 spectropolarimetry without analysis. The data show the development of linear polarization. Distinct polarization profiles were seen only in the O I λ7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the O I λ7773 multiplet and Ca II IR triplet absorption troughs a month later, with the latter showing a peak polarization as high as ∼ 2 %. The intrinsic polarization shows three clear position angles: 80 • for the February continuum, 120 • for the February line feature, and 150 • for the March data. We conclude that there are multiple asymmetric components in the ejecta. We suggest that the supernova has a bulk asymmetry with an axial ratio projected on the sky that is different from 1 by of order 10 %. Furthermore, we suggest very speculatively that a high velocity ejecta component moving faster than ∼ 0.115c (e.g., a jet) contributes to polarization in the February epoch.

The Astrophysical Journal, 2009

Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity h... more Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity have been discovered. Their luminosity requires more than 1 M ⊙ of 56 Ni ejected during the explosion, suggesting that they might have originated from super-Chandrasekhar mass white dwarfs. However, the nature of these objects is not yet well understood. In particular, no data have been taken at late phases, about one year after the explosion. We report on Subaru and Keck optical spectroscopic and photometric observations of the SN Ia 2006gz, which had been classified as being one of these "overluminous" SNe Ia. The late-time behavior is distinctly different from that of normal SNe Ia, reinforcing the argument that SN 2006gz belongs to a different subclass than normal SNe Ia. However, the peculiar features found at late times are not readily connected to a large amount of 56 Ni; the SN is faint, and it lacks [Fe II] and [Fe III] emission. If the bulk of the radioactive energy escapes the SN ejecta as visual light, as is the case in normal SNe Ia, the mass of 56 Ni does not exceed ∼ 0.3 M ⊙. We discuss several possibilities to remedy the problem. With the limited observations, however, we are unable to conclusively identify which process is responsible. An interesting possibility is that the bulk of the emission might be shifted to longer wavelengths, unlike the case in other SNe Ia, which might be related to dense C-rich regions as indicated by the early-phase data. Alternatively, it might be the case that SN 2006gz, though peculiar, was actually not substantially overluminous at early times. Subject headings: white dwarfs-radiative transfer-supernovae: individual (SN 2006gz) 1 Based on data collected at the Subaru Telescope (operated by the National Astronomical Observatory of Japan) and the W. M. Keck Observatory (operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; supported by the W. M. Keck Foundation).

Astronomy & Astrophysics, 2015

Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-su... more Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at ∼300 days after the explosion, and discuss these in the context of constraints on the supernova's progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lowermass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O I]/[Ca II] line ratio with other supernovae.