Evidence for an anticorrelation between the duration of the shallow decay phase of GRB X-ray afterglows and redshift

Table 1:

Selected sample of GRBs with known redshift that presents a shallow decay phase.
GRB	t₂ [ks]	$\alpha_1$	z	$E_{\rm iso} [10^{52}]$ erg	$E_{{\rm peak},i}$ [keV]	Comments
050315	$9.0\pm0.2$	$-0.2\pm0.1$	1.949	-	-	steep phase excluded
050319	$2.7\pm0.1$	$0.1\pm0.2$	3.240	-	-	-
050401	$5.0\pm0.3$	$0.63 \pm0.02$	2.90	$35\pm7^A$	$467\pm110^{(1)}$	-
050505	$6.4\pm0.4$	$0.1\pm 0.1$	4.27	$19.5\pm3.1^N$	$622\pm211^{(2)}$	-
051109A	$2.0\pm0.1$	$0.54\pm0.03$	2.346	$6.5\pm0.7^A$	$539\pm200^{(1)}$	-
060502A	$30\pm2$	$0.43\pm 0.09$	1.51	-	-	-
060526	$20\pm2$	$0.11\pm 0.07$	3.21	$2.6\pm0.3^A$	$105\pm21^{(1)}$	flare excluded
060607A	$12.9\pm0.2$	$0.44\pm 0.02$	3.082	$12.2\pm1.8^N$	$535\pm164^{(2)}$	flare excluded
060614	$47\pm2$	$0.05\pm 0.03$	0.125	$0.21\pm0.09^A$	$55\pm45^{(1)}$	steep phase excluded
060714	$\rm 3.6^{+1.2}_{-0.7}$	$0.24\pm 0.05$	2.71	-	-	flare excluded
060729	$77\pm1$	$0.12\pm 0.02$	0.54	-	-	flare excluded
060814	$9.9\pm0.2$	$0.25\pm0.06$	0.84	$7.0\pm0.7^A$	$473\pm155^{(1)}$	flare excluded
061121	$3.6\pm0.5$	$0.25\pm0.04$	1.314	$22.5\pm2.6^A$	$1289\pm153^{(1)}$	-
070306	$27.2\pm0.8$	$0.11\pm0.02$	1.4959	-		-
070529	$\rm 2^{+2}_{-1}$	$0.7\pm0.1$	2.4996	-	-	-
070611	$\rm 50^{+10}_{-13}$	$0.1\pm 0.1$	2.04	-	-	-
070802	$\rm 5^{+2}_{-1}$	$0.1\pm0.2$	2.45	-	-	-
080310	$4.5\pm0.9$	$0.7\pm0.1$	2.42	-	-	flare excluded
080430	$\rm 15^{+8}_{-3}$	$0.4\pm0.1$	0.767	-	-	-
080605	$0.55\pm0.03$	$0.68\pm0.04$	1.6398	-	-	-
080607	$1.5\pm0.2$	$\rm0.1^{+0.9}_{-0.3}$	3.036	-	-	flare excluded

⁽¹⁾ From Amati et al. (2008); ⁽²⁾ from Nava et al. (2007).