TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1505
SUBJECT: GRB020813: optical and NIR observations
DATE:    02/08/19 09:09:55 GMT
FROM:    Andrea Di Paola at Rome Astron.Obs.-INAF  <dipaola@mporzio.astro.it>

A. Di Paola (1), A. Arkharov (2), V. Larionov (3),
L. A. Antonelli (1)

1) Rome Astronomical Observatory (IT)
2) Pulkovo Observatory (RU)
3) St.Petersburg University (RU)

on the behalf of the GROAR Team, report:

We have imaged the GRB020813 OT (GCN 1471) from the
Campo Imperatore Observatory both with the 60cm
Schmidt telescope at optical wavelengths and with
the 1.1 meters AZT-24 telescope at NIR wavelengths.

Observations started on 2002-08-13 19:50:00 UT
and ended the same day on 23:52:00 UT, respectively
16.1 and 21.1 hours after the burst.

The extremely low elevation (always between 2 and 3
airmasses) and the consequent poor seeing conditions
allow us to barely distinguish between the OT and the
double star located about 3.8" to the North (see
U. Kiziloglu et al. GCN 1488, W. D. Li et al. GCN 1491,
M. Gladder et al. GNC 1495). For this reason the following
magnitudes have to be considered lower limits until
we will complete the subtraction of the field components.

We obatined V, R, I, J and K images at:
2002-08-13 19.42 V-band: OT ~ 19.90 +- 0.20
2002-08-13 19.77 R-band: OT ~ 18.85 +- 0.20
2002-08-13 20.49 I-band: OT ~ 19.90 +- 0.20
2002-08-13 21.61 R-band: OT ~ 19.70 +- 0.20
2002-08-13 22.88 V-band: OT ~ 20.35 +- 0.20
2002-08-13 23.38 I-band: OT ~ 20.15 +- 0.20
and a continuous repetition of J and K images
starting from 18.83 up to 23.88 UT.

We extimated the color indexes between optical and
NIR bands:
  V-J ~ 1.3 +- 0.5
  V-K ~ 3.1 +- 0.5
and the magnitudes at J and K to be about 18.8 and
17.0 respectively.

The magnitudes calibration is obtained from
A. Henden GCN 1503 for the optical points and from
2MASS catalog for the infrared points.

The refined analysis is underway.