GCN Circular 37327

U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory),

Members of: 
GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani.
AAVSO - American Association of Variable Star Observers.
GAC - Gruppo Astrofili Cremonesi.

In a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan), 
Y. Niino (Tokyo University, Institute of Astronomy), 
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report:

We performed optical follow-up observations of the GRB 240828A discovered by the Fermi satellite. 
We used the Baker-Schmidt telescope (Diam 250mm F/3) of the (IAU station 565) Bassano Bresciano Astronomical Observatory (Italy). 

The single Field of the telescope is 41.2' x 30.7'
To cover the uncertainty zone of the satellite position, we performed a mosaic of 9 images in order to cover a rectangle with sides of 2.1 x 1.5 degrees centered on the coordinates J2000 14h 36m, 35d 47'

We performed a total of 9 pointings to cover an area of 3.9 square degrees. For each pointing, 10 images were taken with duration of 20 seconds each. 

The limiting magnitude is CR 17 (CR= Unfiltered with R zero point). 

The sequence of pointing and the taking of images were automated by means of a telescope control software developed at our observatory. 

The image analysis was performed using the subtraction method, with the template from POSS2/UKTSU Red images. 

The observations started 4 hour after the GRB trigger.

For each field, we co-added 10 exposures of 20 sec each.

Start T0+      End T0+      CR lim
4.03 hour     4.81 hour     17

We did not found any credible optical counterpart in the error box of the 
Fermi Satellite. 

Magnitudes were estimated with the pan-STARRS cat 
and are derived using Lupton (2005) equations.
Not corrected for galactic dust extinction.

Reference:
http://www.osservatoriobassano.org

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