[vsnet-grb-info 8101] GRB 090709A: Subaru NIR observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9634
SUBJECT: GRB 090709A: Subaru NIR observation 
DATE:    09/07/09 18:47:52 GMT
FROM:    Nobuyuki Kawai at Tokyo Tech  <nkawai at hp.phys.titech.ac.jp>

K. Aoki, M. Ishii (Subaru Telescope), M. Kuzuhara (Univ. of Tokyo), 
Y. Takahashi (Univ. of Advanced Study) and N. Kawai (Tokyo Tech) 
report on behalf of the Subaru GRB team:

We observed the field of GRB 090709A (Morris et al. GCN 9625)
with MOIRCS on Subaru Telescope in J and K bands under a
cirrus condition, starting at ~9:30 UT on July 9, approximately
2 hours after the burst.
We detected following two objects near the XRT error circle.
Their preliminary magnitudes based on a nearby 2MASS star are following.

object A:  J(Vega)=19.0, K(Vega)=18.2
object B:  J undetected, K(Vega)=18.6

We placed the K band finding chart at

http://www.hp.phys.titech.ac.jp/nkawai/grb/090709/GRB090709.jpg

We further performed spectroscopy for them with the following results:

Object A: zJH spectroscopy, a flat spectrum with no break detected.

Object B: HK and zJH spectroscopy, a continuum detected in K-band,
   no continuum detected in J band, 
   possibly no continuum in H-band but with high background.

Lack of H band continuum could suggest that the object B is at high 
redshift (z~10), though its poor SNR does not allow us to confirm it.
Fading is not confirmed for either of them.

Further NIR/optical observations are strongly encouraged.