GCN Circular 37131

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

Members of:
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/SSV-GRB section.
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 imaged the field of GRB 240809A detected by SWIFT(trigger 1247745) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy.
The observations started 11.38 hours after the GRB trigger, At the end of twilight with our Newton telescope D=450 mm F/D=4.5.

We co-added 150 exposures of 20 sec each (total 50 min).

  Start T0+      End T0+          CR lim
  11.38 hour    12.29 hour         20.6

We detected a (fading) afterglow in the error box of the XRTcandidate (Evans et al., GCN 37110
Not found
 
 
; Wang et al., GCN 37113
Not found
 
 
; Dubay et al., GCN 37114
Not found
 
 
; Jiang et al., GCN 37116
Not found
 
 
; V. Lipunov et al., GCN 37117
Not found
 
 
; Gottumukkala et al., GCN 37122
Not found
 
 
; Shilling & Evans, GCN 37123
Not found
 
 
; Mohan et al., GCN 37125
Not found
 
 
; Zheng & Filippenko, GCN 37127
Not found
 
 
; B. Schneider et al., GCN 37129
Not found
 
 
) at the following position (+/- 3 arcsec):

RA (J2000.0) =   15 50 10.46
DEC(J2000.0) =  -02 19 04.6

The results of our photometry are:
---------------------------------------------
    Date UT          Exp        Afterglow
    Middle          (Min)        CR-mag
---------------------------------------------
2024 08 09.84773      50       19.7 +/- 0.2

---------------------------------------------
CR magnitude is unfiltered with R zero point.


Comparison stars used:
------------------------------
Pan-STARRS obj ID        R-Mag
------------------------------
105212375756448208      16.639
105202375684658035      17.916
105202375288851708      17.912
105192375172794156      17.312
105182375066235940      17.998
------------------------------

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

Reference:
http://www.osservatoriobassano.org/grb.asp

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