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GCN Circular 3484

Subject
GRB 050525, spectral lag pseudo-redshift
Date
2005-05-25T22:19:26Z (19 years ago)
From
Jay Norris at NASA-GSFC/LHEA <jnorris@lheapop.gsfc.nasa.gov>
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.
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