TY - JOUR
T1 - Spectral Evolution of the GRB 030329 Afterglow
T2 - Detection of the Supernova Nebular Phase Emissions
AU - Kosugi, George
AU - Mizumoto, Yoshihiko
AU - Kawai, Nobuyuki
AU - Yoshida, Atsumasa
AU - Kawabata, Koji S.
AU - Totani, Tomonori
AU - Iye, Masanori
AU - Sekiguchi, Kazuhiro
AU - Aoki, Kentaro
AU - Ohyama, Youichi
AU - Aoki, Wako
AU - Kobayashi, Naoto
AU - Komiyama, Yutaka
AU - Noumaru, Jun'ichi
AU - Ogasawara, Ryusuke
AU - Sakamoto, Takanori
AU - Shirasaki, Yuji
AU - Takata, Tadafumi
AU - Tamagawa, Toru
AU - Torii, Ken'ichi
AU - Urata, Yuji
AU - Watanabe, Jun ichi
AU - Yamada, Toru
AU - Qiu, Yulei
PY - 2004/1/1
Y1 - 2004/1/1
N2 - GRB 030329 is the first Gamma-ray burst event for which a connection with a supernova (SN 2003dh) has been confirmed spectroscopically in its early phase. We present optical spectroscopy of this object 40 and 85 days after the burst (35 and 73 rest-frame days, respectively) obtained with the Subaru 8.2-m telescope. After subtracting the host galaxy template spectrum, the second-epoch spectrum shows nebular-phase emission lines emerging from the dominated photospheric-phase spectrum. The transition from the photospheric phase to the nebular phase has just started, or was slowly progressing at the time of our second-epoch observations. Our spectral analysis of the nebular-phase emission lines suggests that the explosion of the progenitor of the GRB 030329 was aspherical, and that the axis of an asphericity is well aligned to both the GRB relativistic jet and our line of sight. Although the decay index and the color evolution in the rest frame during our two epochs are very consistent with those of the Type le supernovae SN 1998bw and SN 1997ef, the nebular-phase lines emerged slightly earlier than in the case of these supernovae. These results infer that the most important factor that distinguishes SNe with GRB from SNe without GRB is the scale of the jet activity, or a viewing-angle effect, or both of them.
AB - GRB 030329 is the first Gamma-ray burst event for which a connection with a supernova (SN 2003dh) has been confirmed spectroscopically in its early phase. We present optical spectroscopy of this object 40 and 85 days after the burst (35 and 73 rest-frame days, respectively) obtained with the Subaru 8.2-m telescope. After subtracting the host galaxy template spectrum, the second-epoch spectrum shows nebular-phase emission lines emerging from the dominated photospheric-phase spectrum. The transition from the photospheric phase to the nebular phase has just started, or was slowly progressing at the time of our second-epoch observations. Our spectral analysis of the nebular-phase emission lines suggests that the explosion of the progenitor of the GRB 030329 was aspherical, and that the axis of an asphericity is well aligned to both the GRB relativistic jet and our line of sight. Although the decay index and the color evolution in the rest frame during our two epochs are very consistent with those of the Type le supernovae SN 1998bw and SN 1997ef, the nebular-phase lines emerged slightly earlier than in the case of these supernovae. These results infer that the most important factor that distinguishes SNe with GRB from SNe without GRB is the scale of the jet activity, or a viewing-angle effect, or both of them.
KW - Cosmology: early universe
KW - Gamma rays: bursts
KW - Gamma rays: individual (GRB 030329)
KW - Gamma rays: observations
KW - Stars: supernovae: individual (SN 2003dh)
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U2 - 10.1093/pasj/56.1.61
DO - 10.1093/pasj/56.1.61
M3 - Article
AN - SCOPUS:1942440974
VL - 56
SP - 61
EP - 68
JO - Publications of the Astronomical Society of Japan
JF - Publications of the Astronomical Society of Japan
SN - 0004-6264
IS - 1
ER -