P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), V. D'Elia
(ASDC), M. de Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), V.
Mangano (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne (U.
Leicester) and C. Pagani report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 140512A (Pagani et al. GCN
Circ. 16249), from 87 s to 12.6 ks after the BAT trigger. The data
comprise 841 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
The late-time light curve (from T0+4.6 ks) can be modelled with a
power-law decay with a decay index of alpha=1.06 (+/-0.09).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.460 (+0.029, -0.016). The
best-fitting absorption column is consistent with the Galactic value
of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.80 (+/-0.07) and a best-fitting absorption column
of 2.02 (+0.28, -0.26) x 10^21 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum is 4.0 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.02 (+0.28, -0.26) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 3.4 sigma
Photon index: 1.80 (+/-0.07)
If the light curve continues to decay with a power-law decay index of
1.06, the count rate at T+24 hours will be 0.15 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-12 (7.4 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
This circular is an official product of the Swift-XRT team.