{
  "eventType": [
    "GRB",
    "Optical Transient"
  ],
  "format": "text/plain",
  "submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
  "subject": "GRB 260909A: SVOM/VT optical upper limits",
  "createdOn": 1788973331745,
  "eventId": "GRB 260909A",
  "bibcode": "2026GCN.45539....1L",
  "body": "H. L. Li,  Y. N. Ma, C. Wu, L. P. Xin, Y. L. Qiu, Z. H. Yao, J. R. Xu, L. J. Chen, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu), C. Plasse (HKU) and A. Li (BNU) report on behalf of the SVOM/VT team.\n\nSVOM/VT performed an automatic slew on the burst GRB 260909A detected by SVOM/ECLAIRs (sb26090910, Saccardi et al., GCN 45534), SVOM/MXT (Saccardi et al., GCN 45534) and SVOM/GRM (Wang et al., GCN 45538).  The observation started at 2026-09-09T11:22:16 UTC, i.e. 255 sec in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n \nWith X band downlinked data, no credible candidates were identified in our single or stacked images within the error box of MXT (Saccardi et al., GCN 45534) compared to the Legacy Survey. \n\nThe following measurements are in the AB magnitude and are not corrected for Galactic extinction:\n\nMid time | Band | Exposure Time |  3-sigma upper limit\n9.6 min    VT_B     12*50  sec       > 23.0 mag    \n9.3 min    VT_R     13*50  sec       > 22.8 mag\n1.5  hr    VT_B     50*50  sec       > 23.3 mag    \n1.5  hr    VT_R     50*50  sec       > 23.2 mag\n \nOur results are consistent with the non-detections from SVOM/C-GFT (Guan et al., GCN 45535) and Xinglong 2.16m telescope (Ma et al., GCN 45536).\n\nDeeper optical and near-infrared follow-ups are encouraged.\n\nFor the Mondy candidate (Pankov et al., GCN 45537), we notice that there is a catalog source at this position in the Legacy Survey with magnitudes g=22.51, r=21.72, i=21.41, z=21.33.\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.",
  "circularId": 45539,
  "submittedHow": "web"
}