[vsnet-grb-info 4214] GRB 070110 declared a Burst of Interest by Swift team

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6014
SUBJECT: GRB 070110 declared a "Burst of Interest" by Swift team
DATE:    07/01/12 21:44:43 GMT
FROM:    Hans Krimm at NASA-GSFC  <krimm at milkyway.gsfc.nasa.gov>

H. A. Krimm (GSFC/USRA) , P. Boyd (GSFC), V. Mangano (INAF-IASFPA),
F. Marshall (GSFC), B. Sbarufatti (INAF-IASFPA), N. Gehrels (GSFC)
report on behalf of the Swift Team

Based on its unusual afterglow light curve, the Swift team declares
GRB 070110 to be a "burst of interest".  Although the burst is
59 degrees from the Sun and moving closer to the Sun, we will
continue observations of the afterglow in the U filter over the next
several days.  We  encourage multiwavelength observations of this
unusual burst throughout its lightcurve.

Swift observations of GRB 070110 are discussed in GCN Report 26.2
(http://gcn.gsfc.nasa.gov/report_archive.html)

As reported previously, after a very steep drop, the XRT light curve
started to rise at T+35 ksec, reaching 3.2 X 10^-2 counts/sec.
Then between T+45 ksec and T+75 ksec, the light curve again turned
over, dropping to 6 X 10^-3 counts/sec at 100 ksec, before flattening
again.  Although flares have been observed in other bursts at
times > 10 ksec, such behavior (a steep drop followed by a slow rise)
has not before been observed in a Swift burst (see for example
P. O'Brien et al (2006), ApJ 647, 1213).

The UVOT light curve is even more extraordinary.  The afterglow
was originally detected at V=20 at T+104 sec and continues to be
detectable in all visible filters (V, B and U) with a common power
law decay index of -0.47 +- 0.02 in all three filters.  At T+203 ksec,
the afterglow is seen at V=21.6. Thus the optical light curves do not show
any of the extreme variability seen in the X-rays.  It is very rare that
a burst which was first detected at V=20 is still detectable at
T >200 ksec. The afterglow was not detected in the UVW1 filter, with
a 3-sigma upper limit of 22.26 for a 4071-sec exposure beginning at T+75 ks.
This non-detection is consistent with the redshift z=2.352 reported 
for the burst
(Malesani et al, GCN 6010).