Talk detail

Participant	Tsutsui, Ryo
Institution	The University of Tokyo - Hongo, 7-3-1 - Bunkyo-ku - Tokyo - Japan

Session	OC3	Accepted		Order	Time
Talk	Oral abstract	Title	Are gamma-ray bursts as precise distance indicators as Type Ia Supernovae?
Co-authors
Abstract	There are some empirical correlations between spectral peak energy (Ep) and brightness of prompt emission of long gamma-ray bursts (LGRBs). These correlations are expected to be distance indicators up to redshift z>2 where no other distance indicators have been observed. However the large scatter around best fit functions of these correlations restricts the precision of distance measurements from LGRBs. In this talk, we would like to introduce our studies about the spectral peak energy (Ep) - peak luminosity (Lp) correlation of LGRBs. We have shown that there are many origins of the systematic errors of the observables, and an additional parameter, luminosity time TL, reduces the scatter of the Ep-Lp correlation. Besides, we have found there are at least two subclasses in LGRBs divided by morphology of cumulative light curve of prompt emission. As a result, we have succeed to remove systematic errors of the Ep-Lp correlation and the Ep-TL-Lp correlation have became an ideal distance indicator. We would like to show the constraint on the density parameters of LCDM universe from 10 GRBs at z >1.4 is as strong as the one from 557 Type Ia Supernovae at z<1.4.