V. Mangano (INAF/IASF Pa), B. Sbarufatti (INAF/OAB - IASF Pa) report on
behalf of the Swift-XRT team:
We have analysed 4.9 ks of XRT data for GRB 101201A (Cummings et al.
GCN Circ. 11429), from 51.2 ks to 69.7 ks after the BAT trigger. The
data are entirely in Photon Counting (PC) mode. Using 3879 s of PC mode
data and 3 UVOT images, we find an enhanced XRT position (using the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 1.96750, -16.18540 which is equivalent to:
RA (J2000): 00h 07m 52.21s
Dec(J2000): -16d 11' 07.4"
with an uncertainty of 1.9 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=3.80 (+0.03, -1.25).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.4 (+0.7, -0.6). The
best-fitting absorption column is 8 (+14, -6) x 10^20 cm^-2,
consistent with the Galactic value of 2.2 x 10^20 cm^-2 (Kalberla et
al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.2 x 10^-11 (4.6 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 8 (+14, -6) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 2.4 (+0.7, -0.6)
If the light curve continues to decay with a power-law decay index of
3.80, the count rate at T+24 hours will be 4.9 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-13 (2.2 x 10^-13) 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.