Outliers in Spectral Time Lag-Selected Gamma Ray Bursts

Abstract

It is possible that astrophysical samples are polluted by some outliers, which might belong to a different sub-class. By removing the outliers, the underlying statistical features may be revealed. A more reliable correlation can be used as a standard candle relationship for cosmological study. We present outlier searching for gamma ray bursts with the Partitioning Around Medoids (PAM) method. In this work, we choose three parameters from the sample, with all of them having rest-frame spectral time lag (τlag,i). In most cases, the outliers are GRBs 980425B and 030528A. Linear regression is carried out for the sample without the outliers. Some of them have passed hypothesis testing, while others have not. However, even for the passed sample, the correlation is not very significant. More parameter combinations should be considered in future work.