[AAVSO-HEN] GRB 070406: Swift XRT refined analysis

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  6298
SUBJECT: GRB 070406: Swift XRT refined analysis
DATE:    07/04/16 16:15:33 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

E. Troja (U. Leicester/INAF-IASFPa), K. L. Page (U. Leicester), S. McBreen
(MPE), D. N. Burrows (PSU) and N. Gehrels (NASA/GSFC) report on behalf of
the Swift XRT team:

Swift monitored the field of GRB 070406 (Cummings et al., GCN Circ. 6247)  
for nine days, starting 20.6 hr after the burst. From the analysis of the
full data set, consisting of 115 ks of total exposure in XRT/Photon
Counting mode, no X-ray afterglow is detected within the BAT refined error
circle (Krimm et al., GCN Circ.6261).

The two X-ray sources (S1 and S2 - Troja et al., GCN Circ. 6265) inside
the BAT error region do not show a fading behavior, therefore none of them
can be identified as the X-ray counterpart of GRB 070406.

The non detection in the first follow-up observation (from T0+20.6 hr to
T0+41.9 hr) implies an X-ray afterglow fainter than 7.5e-04 cts/s (3-sigma
upper limit). Assuming a power-law spectral shape with photon index 2 and
a Galactic absorption of 1.8e20 cm-2 (Dickey & Lockman, 1990), it
corresponds to an observed (unabsorbed) limiting flux of 2.7e-14 (2.9e-14)
erg cm-2 s-1 in the 0.3-10 keV band.

No further Swift observations are planned.

This circular is an official product of the Swift XRT Team.