TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3484 SUBJECT: GRB 050525, spectral lag pseudo-redshift DATE: 05/05/25 22:19:26 GMT FROM: Jay Norris at NASA-GSFC/LHEA J. Norris, S. Barthelmy, N. Gehrels (GSFC), J. Cummings (GSFC/NRC), D. Band (GSFC/UMBC), L. Barbier (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC), J. Tueller (GSFC) Analysis of the Swift/BAT light curves, between channels 100-350 keV and 25-50 keV, yields an estimate of the spectral lag of 0.124 +- 0.006 seconds for GRB 050525 (GCN 3466, Band et al.; (GCN 3479, Cummings et al.). Assuming the lag-luminosity relation (Norris et al. 2000, ApJ, 534, 248), using the Band model spectral parameters measured during the 1-second peak of the burst's light curve -- alpha = -1.0, beta = -8.9, Epeak = 79 keV, and the 1-second peak flux, 48 photon/cm^2/s, 15-350 keV -- we estimated a spectral-lag pseudo redshift of z = 0.72 +- 0.15, in broad agreement with the spectroscopic redshift, z = 0.606, reported by Foley et al. (GCN 3483). Uncertainty in the high-energy spectral shape, and the difference between the BATSE and BAT bandpass dependences of the lag-luminosity relation on peak flux, combine to require the error of order delta_z = 0.15.