GCN Circular 886

P. Vreeswijk, E. Rol (U. of Amsterdam), C. Packham (U. of Florida),
N. Tanvir (U. of Hertfordshire), C. Kouveliotou (MSFC/USRA), R. Wijers
(SUNY) and J. Knapen (ING/U. of Hertfordshire), report on behalf of a
larger collaboration:

We observed the field of GRB 001109 [1] in J, H and Ks with INGRID on
the 4.2m William Herschel Telescope on La Palma, Canary Islands on
Nov. 9.8 and 11.8 UT, respectively 10 and 59 hours after the burst.
The 50" radius error circle of the reported X-ray afterglow of 
GRB 001109 [2] is located at the center of our 4.2'x4.2' images.

We observed the UKIRT faint standard #30 [see 3] to calibrate the
field. The stellar FWHM in the co-added frames ranges from 0.9" to
1.3" (pixelsize=0.25").  The first table below shows the log of the
observations, including the estimated 3-sigma limiting magnitude
(using an aperture diameter twice the size of the FWHM).

At the position of the radio source detected in the field [4], we
observe extended emission, consisting of a bright component (with a
PSF FWHM significantly larger than that of point sources in the
field), and a fainter peak, separated by roughly 1". The magnitudes
that we measure for this emission (using an aperture radius of 2.5"),
are also listed in the table. Within the errors (which do not include
the uncertainty in the calibration), this source does not vary. This
confirms the expectation [5] that the emission from this location is
probably not related to the GRB.


         UT date   filter  exptime   lim. mag.  radio source
 -----------------------------------------------------------
 2000 Nov.  9.81     J       300s      21.3	18.64 (0.05)
	    9.80     H       750s      21.0	17.96 (0.03)
	    9.79     Ks      750s      19.9	16.96 (0.04)

	   11.86     J       600s      21.4	18.70 (0.05)
	   11.82     H       600s      20.7	17.93 (0.08)
	   11.83     Ks      600s      19.4	17.07 (0.07)


Furthermore, after close inspection of the images by eye and by
comparing the aperture magnitudes of all the detectable objects
between the two epochs, we do not find an afterglow candidate.

To our knowledge, our images present the deepest near-infrared upper
limit on a GRB afterglow brightness to date. The table below shows all
GRB afterglow near-IR detections and upper limits (that we could find)
with observations performed within 3 days of the burst occurrence.  It
is clear that our early deep observations would have easily discovered
any of the detections in the table, and that they are both earlier and
deeper than the reported upper limits. This result suggests that at
least some bursts are intrinsically faint in the near-IR and that the
dust obscuration explanation for the GRB afterglow non-detections in
the optical may not be valid in all cases, unless this burst occurred
at a redshift large enough for the optical/UV extinction in the rest
frame to move into the K band regime in the observer's frame.


 GRB		magnitude	       hrs. since burst	    reference
 --------------------------------------------------------------------
 971214		J=20.3			     11		      [6]
 980329		J~19.2			     16		      [7]
 980703		H=17.6			     30		      [8]
 990123		K=18.3			     29		      [9]
 990510		J=17.1, H=16.4, K=16.6	     14		      [10]
 990705		H=16.6		 	      7		      [11]
 991216		J=16.8, K=15		     13		      [12]
		H=17.2			     35		      [13]
 000214		K>18.2			     32		      [14]
 000301C	K~17.4			     50		      [15]
 000418		K~17.5			     60		      [16]
 000516		J>20.5, K>17.5		     17		      [17]
 000615		H>20.5			     17		      [18]
 000926		K~19			     72		      [19]


Finally, we estimate a rough optical upper limit by extrapolating our
H band upper limit to the R band, assuming a typical unreddened
afterglow spectrum with a slope of -0.8, obtaining R > 23.1.
Extinction intrinsic to the burster host galaxy is not included, which
can substantially increase this R band limit.

 References:

 1. Piro, L. et al. 2000, GCN No. 879
 2. Amati, L. et al. 2000, IAU Circ. 7519
 3. http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/calib/fs_newJHK.html
 4. Taylor, G.B. et al. 2000, GCN No. 880
 5. Stanek, K.Z. et al. 2000, GCN No. 881
 6. Tanvir, N. et al. 1997, IAU Circ. 6796
 7. Mannucci, F. et al. 1998, GCN No. 46
 8. Vreeswijk, P. et al. 1999, ApJ, 523, 171
 9. Bloom, J.S. et al. 1999, GCN No. 240
10. Rol, E. et al. 2001, in prep.
11. Masetti, N. et al. 2000, A&A, 354, 473
12. Garnavich, P. et al. 2000, ApJ, 543, 61
13. Rol, E. et al. 2001, in prep. 
14. Rhoads, J. et al. 2000, GCN No. 564
15. Klose, S. et al. 2000, GCN No. 572
16. Stecklum, B. et al. 2000, GCN No. 654
17. Antonelli, A. et al. 2000, GCN No. 708
18. Palazzi, E. et al. 2000, GCN No. 727
19. Kobayashi, N. et al. 2000, GCN No. 821