GCN Circular 2916

NIR Observations of GRB 041219

F. Hearty (Colorado), D. Q. Lamb (Chicago), J. Barentine (APO), P. A.
Price (Hawaii), S. Beland (Colorado), E. L. Turner (Princeton), R.
McMillan (APO), J. Dembicky (APO), B. Ketzeback(APO), and D. G. York
(Chicago) report on behalf of the ARC team of the FUN GRB
collaboration:

We observed the NIR afterglow (Blake and Bloom, GCN Circular No. 2870)
of GRB 041219, a burst localized by Integral (Gotz et al., GCN Circular
No. 2866) and Swift-BAT (Barthelmy et al., GCN Circular No. 2874), on
the night of December 20th, using C-NIC (formerly NIC-FPS) on the ARC
3.5-meter telescope at Apache Point Observatory.  The observation began
at 01.05 UT, 47.25 hours after the burst, and consisted of a series of
120, 20, and 20-second exposures in J, H, and Ks, respectively.  We
constructed stacked images corresponding to 20-minute exposures in J
and H, and a 40-minute exposure in Ks.  We detect the afterglow in all
three filters; the magnitudes are J = 19.9 +/- 0.2, H = 18.9 +/- 0.1,
and Ks = 17.6 +/- 0.2.  We thus confirm that the afterglow is heavily
reddened, as previously noted by Blake and Bloom (GCN Circular No.
2870).  We also confirm that the afterglow had faded significantly in
comparison with the earlier NIR observations reported by Blake and
Bloom (GCN Circular No. 2870) and Moon, Cenko, and Adams (GCN Circular
Nos. 2876 and 2884), in agreement with the conclusion of Bloom et al.
(GCN Circular No. 2893).  As noted by Bloom et al. (GCN Circular No.
2893), the IR afterglow is located 2.5 arcseconds south-south-west of a
faint compact source that is visible in J, H, and Ks.

Using Schlegel et al. (1998), the estimated extinction in the direction
of GRB 041219 is E(B-V) = 1.8 mag, corresponding to A_lambda values of
J = 1.6, H = 1.0, K = 0.65 mag.  These values give J-H = 0.6, H-K =
0.4, and  J-K = 1 mag, compared to our measured values of J-H = 1.0,
H-K = 1.3, and J-K = 2.3 mag.  Although our results indicate greater
reddening than that estimated using Schlegel et al. (1998), the
estimated value of E(B-V) is unreliable because GRB 041219 lies very
close to the Galactic plane (b = 0.6 [deg]).  We therefore cannot say
that there is more reddening than can be accounted for by Galactic
extinction.  However, our results show that the drop-off with
decreasing wavelength is gradual and therefore is unlikely to be due to
absorption by hydrogen in the host galaxy or along the line of sight to
the host galaxy.  Consequently, the burst is unlikely to lie at a very
high redshift (z > 5).

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