Ryo Tsutsui, Takashi Nakamura, Daisuke Yonetoku, Keitaro Takahashi, Yoshiyuki Morihara
We argue the possibility to improve the statistical significance of
fundamental plane of long gamma-ray bursts (LGRBs), which is a correlation
between the spectral peak energy $E_{\rm p}$, the luminosity time $T_{\rm L}$
($\equiv E_{\rm iso}/L_{\rm p}$ where $E_{\rm iso}$ is isotropic energy) and
the peak luminosity $L_{\rm p}$, using the morphology of cumulative light curve
of the prompt emission. We parametrize the morphology by the absolute deviation
from constant luminosity ($ADCL$) and derive the value for 40 LGRBs which have
spectropic redshifts, spectral parameters determined by the Band model,
1-second peak fluxes, fluences, and 64 msec resolution light curves whose peak
counts are 10 times larger than background fluctuations. We find that the
correlations for GRBs with small and large $ADCL$ ($ADCL < 0.17$ and $ADCL >
0.17$, respectively) are statistically more significant compared with one
derived from all samples and are given by $L_{\rm p}=10^{52.51\pm 0.02}(E_{\rm
p}/10^{2.71}{\rm keV})^{1.86\pm 0.03}(T_{\rm L}/10^{0.86}{\rm
sec})^{0.35\pm0.09}$ with $\chi^2_{\nu}=14.87/18$ and $L_{\rm
p}=10^{52.93\pm0.04}(E_{\rm p}/10^{2.71}{\rm keV})^{1.76\pm 0.05}(T_{\rm
L}/10^{0.86}{\rm sec})^{0.71\pm 0.17}$ with $\chi^2_{\nu}=7.21/9$,
respectively. This fact implies the existence of subclasses of LGRBs
characterized by the value of $ADCL$. Also there is a hint for the existence of
the intermediate-$ADCL$ class which deviates from both fundamental planes.
Because both relations are so tight that our result provides a new accurate
distance measurement scheme up to the high redshift universe.
View original:
http://arxiv.org/abs/1201.2763
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