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GCN Circular 34488

Subject
GRB 230818A: Bassano Bresciano Observatory optical observations
Date
2023-08-19T14:56:53Z (8 months ago)
From
Ulisse Quadri at Bassano Bresciano Obs <oabb@ulisse.bs.it>
Via
legacy email
U.Quadri and  L.Strabla (Bassano Bresciano Astronomical Observatory),

Members of: 
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili-GRB.
GAC - Gruppo Astrofili Cremonesi.


We imaged the field of GRB 230818A detected by SWIFT(trigger 1186032)
with the robotic telescope of (IAU station 565) Bassano Bresciano 
Observatory, Italy. 

The observations started 13.61 min after the GRB trigger,  
with our Newton automated telescope D=250 mm F/D=4.8.

Weather conditions were good.

We co-added 3 series of 10 exposures of 60 sec each.

We detected afterglow in the error box of the XRTcandidate.
(Fermi GBM team, GCN 34478; Tohuvavohu et al., GCN 34479; 
Ben Gompertz et al., GCN 34480; V. Lipunov et al. GCN 34482;
A. S. Moskvitin et al., GCN 34483; D.B. Malesani et al., GCN 34485; 
N. Pankov et al., GCN 34487) at the following position (+/- 2 arcsec):

RA (J2000.0) =  19 03 33.21 
DEC(J2000.0) = +40 53 49.5


Our photometry of the afterglow are:


Date U.T.            R mag    Sigma
------------------------------------
2023 08 18.99405     18.90    0.07
2023 08 19.00126     19.21    0.07
2023 08 19.00154     19.47    0.06
----------------------------------


COMPARISON STARS
--------------------------------------------------------------------
   pan-STARRS ID          g           r           i         Rc
--------------------------------------------------------------------
157072858562487290     17.4025     16.7800     16.5376     16.56
157052858895609613     16.8323     16.3279     16.1482     16.13
157072859081709765     15.0561     14.7054     14.5820     14.53
157092859169446573     16.9397     16.4745     16.2972     16.28
157102858906415897     17.0217     16.4894     16.2798     16.28
157062859601321798     15.7561     15.2872     15.0934     15.09
--------------------------------------------------------------------

Magnitudes were estimated with the Pan-STARRS cat. 
Rc mag are derived using Lupton (2005) equations.

Not corrected for galactic dust extinction.

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

The message may be cited.



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