GCN Circular 6221

E.  Rol,  N. Tanvir (Leicester), N.  Mirabal  (Columbia), K.  Wiersema
(Amsterdam),  J.P.   Halpern   (Columbia),  A.   Levan  (Warwick),  R.
Chapman (Hertfordshire), A.  Melandri (Liverpool JMU) and D.  Pinfield
(Hertfordshire), report on behalf of a larger collaboration:

We  re-observed  the position  of  the  X-ray  afterglow of  GRB070223
(Vetere  et al,  GCN report  35.1) with  the LIRIS  instrument  on the
William  Herschel Telescope,  between  7.99 and  8.08  days after  the
burst. Our J  and K images do  not show any source inside  the XRT 90%
error  circle. As our  observations are  considerably deeper  than the
first epoch  LIRIS observations reported by Castro-Tirado  et al (GCNC
6168; private  communication), we conclude the source  reported is the
nIR afterglow of GRB070223.

We also  re-examined the optical  images taken with the  MDM telescope
(Mirabal et  al., GCNC 6162), and  find a faint optical  source at the
position of  the nIR afterglow. We  point out that this is a different
source than the one located at RA (J2000) = 10 13 48.19, Dec (J2000) =
43 07 54.7  (S1, GCNC 6162), which now also  falls outside the revised
XRT position (Vetere et al.).

We derive a position for the optical afterglow of (J2000):

   RA  =  10 13 48.39
   Dec = +43 08 00.7

which   fully   agrees   with   the   X-ray   position   (GCN   report
35.1).  Astrometry was done  relative to  the SDSS  (Cool et  al, GCNC
6128), and errors are about 0.3 arcsecond in each coordinate.

The latest MDM image is posted at
http://www.astro.columbia.edu/~mirabal/grb070223mdm.jpg