GCN Circular 35121

M. D. Fulton (QUB), S. Srivastav, S. J. Smartt (Oxford/QUB), J. H. Gillanders (Oxford), K. C. Chambers, M. E. Huber, A. S. B. Schultz (IfA, Hawaii), K. W. Smith, D. R. Young, M. Nicholl, M. McCollum, T. Moore, S. Sim, J. Weston, A. Aamer, C. R. Angus, X. Sheng (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), J. Sommer (LMU/QUB), H. Stevance, L. Rhodes, S. Ramaiya, A. Andersson (Oxford), T. de Boer, J. Herman, J. Fairlamb, H. Gao, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii), T.-W. Chen (NCU), A. Rest (STScI), C. Stubbs (Harvard) report:

We observed the field of GRB 231117A (Laha et al., GCN 35071
Not found
 
 
; Navaneeth et al., GCN 35072
Not found
 
 
; Beardmore et al., GCN 35074
Not found
 
 
; Cattaneo et al., GCN 35075
Not found
 
 
; Svinkin et al., GCN 35079
Not found
 
 
; Cheung et al., GCN 35081
Not found
 
 
; Dafcikova et al., GCN 35095
Not found
 
 
) with Pan-STARRS1 (Chambers et al., 2016) on two nights in the grizy filters, with the exposures beginning on MJDs 60266.255617 and 60267.271553.

We apply the Pan-STARRS1 reference frames for image subtraction and in all exposures, the afterglow candidate identified by Yang et al. (GCN 35083
Not found
 
 
) as AT2023yba
Not found
 
 
 is well detected in griz and marginally in y. We confirm a clear and significant fading in all bands in a comparison between the two nights of:

delta-g = 1.5 +/- 0.2
delta-r = 1.3 +/- 0.2
delta-i = 1.2 +/- 0.2
delta-z = 1.1 +/- 0.2

The latest r-band magnitude at 60267.282458 is r = 22.0 +/- 0.2. This confirms the fast-fading nature of the optical transient AT2023yba
Not found
 
 
, indicating this optical source, discovered by Yang et al. (GCN 35083
Not found
 
 
), is very likely the afterglow of GRB 231117A.

Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and Grant No. NNX14AM74G issued through the SSO Near-Earth Object Observations Program. Data are processed at Queen's University Belfast enabled through the STFC grants ST/P000312/1 and ST/T000198/1.