X-Ray Plateaus in Gamma-Ray Burst Afterglows and Their Application in Cosmology

For gamma-ray bursts (GRBs) with a plateau phase in the X-ray afterglow, a so-called L-T-E correlation that tightly connects the isotropic energy of the prompt GRB (E (gamma,iso)) with the end time of the X-ray plateau (T (a) ) and the corresponding X-ray luminosity at the end time (L (X)) has been found. Here we show that there is a clear redshift evolution in the correlation. Furthermore, because the power-law indices of L-X and E (gamma,iso) in the correlation function are almost identical, the L-T-E correlation is insensitive to cosmological parameters and cannot be used as a satisfactory standard candle. On the other hand, based on a sample including 121 long GRBs, we establish a new three-parameter correlation that connects L (X), T (a) , and the spectral peak energy E-p, i.e., the L-T-E (p) correlation. This correlation strongly supports the so-called Combo-relation established by Izzo et al. After correcting for the redshift evolution, we show that the de-evolved L-T-E (p) correlation can be used as a standard candle. By using this correlation alone, we are able to constrain the cosmological parameters as Omega(m)=0.389(-0.141)(+0.202)(1 sigma) for the flat Lambda CDM model, or Omega(m)=0.369(-0.191)(+0.217) w=-0.966-0.678+0.513

Automated summary

A tight correlation between the isotropic energy of prompt GRBs and the X-ray afterglow has been found, but it shows clear redshift evolution. A new three-parameter correlation, known as L-T-E (p) correlation, connecting X-ray luminosity, end time of plateau, and spectral peak energy Ep, can serve as a standard candle after correcting for redshift evolution. This correlation alone can be used to constrain cosmological parameters.