V. D'Elia (ASDC), F. E. Marshall (NASA/GSFC), L. Izzo (URoma/ICRA) &
D. Malesani (DARK/NBI) report on behalf of the Swift team:
Following the report of a potential optical afterglow iPTF14cyb
(Bhalerao et al., GCN Circ. 16442) to the Fermi/GBM-detected burst GRB
140623A (von Kienlin, GCN Circ. 16450), Swift began a follow-up
observation of the iPTF field.
We have analyzed all the 3.0 ks of XRT data for GRB 140623A, from
38.7 ks to 49.6 ks after the Fermi/GBM trigger. The data are entirely
in Photon Counting (PC) mode. An X-ray source is detected at a
position consistent with the candidate optical afterglow (Bhalerao et
al., GCN Circ. 16442) within the Fermi/GBM error circle.
Using 1153 s of PC mode data and 1 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 = 225.47927, +81.19049
which is equivalent to:
RA (J2000): 15h 01m 55.02s
Dec(J2000): +81d 11' 25.7"
with an uncertainty of 5.8 arcsec (radius, 90% confidence). This
position is 5.0 arcsec from the the optical counterpart iPTF14cyb, and
consistent with it. We cannot determine at the present time whether
the source is fading.
The results of the XRT-team automatic analysis are available at
The Swift/UVOT began settled observations of the field of GRB 140423A
38708 s after the GBM trigger. No optical afterglow consistent with
the optical position (Bhalerao et al. GCN Circ. 16442) is detected in
the initial UVOT exposures. Preliminary 3-sigma upper limits using the
UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358,
Filter T_start(s) T_stop(s) Exp(s) Mag
u 38708 44173 925 >22.0
white 38926 44863 851 >21.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.037 in the direction of the burst
(Schlegel et al. 1998).
This circular is an official product of the Swift team.