[AAVSO-HEN] GRB 070621: TAROT Calern observatory optical observations

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TITLE:   GCN CIRCULAR
NUMBER:  6563
SUBJECT: GRB 070621: TAROT Calern observatory optical observations
DATE:    07/06/22 01:29:39 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 070621 detected by SWIFT
(trigger 282808) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 23.5s after the GRB trigger
(6.4s after the notice). The elevation of the field increased from
from 3 degrees above horizon and weather conditions
were poor.

The date of trigger : t0 = 2007-06-21T23:17:39.840

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT at the XRT location
(Sbarufatti et al. GCNC 6560) with a limiting magnitude of:
t0+23.5s to t0+83.5s : R > 14.9

The second image is 30.0s exposure in tracking mode:
t0+90.3s to t0+120.3s : R > 15.4

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

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