{
  "body": "C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), M. Dennefeld (IAP/Sorbonne U.), J. L. Atteia (IRAP), J. Rodriguez (CEA), F. Cangemi (APC), A. Coleiro (APC), Y. Degot-Longui (Pytheas/OHP), J. Balcaen (Pytheas/OHP), report on behalf of a larger collaboration:\n\nWe observed the field of the SVOM sb25061218 X-ray transient (Rodriguez et al., GCN 40712) using the T120cm and the T193cm equipped with the MISTRAL spectro-imager at Observatoire de Haute-Provence (France). \n\nOur T120 observations consisted of multiple epochs from 2025-06-12T22:07 to 2025-06-13T00:46 UT (from 1.52 to 4.17 hr after the trigger) in r-band and covered both uncatalogued X-ray sources seen with Swift/XRT (Evans et al. GCN 40721). We examined the sources visible at the XRT #1 and #2 positions and noted a rebrightening of ~0.3 mag of the SIMBAD object [VV2006] J131446.6+544804 compared to SDSS (r = 18.66 +/- 0.02) and PanStarrs (r = 18.65 +/- 0.01) surveys, possibly associated with the XRT source #1.\n\nThe magnitudes derived for that source (measured with STDWeb/STDPipe tools (Karpov 2025)) are:\ndate-obs (UT) | exposure time (min) | band, mag (AB) | mag err\n2025-06-12T22:07 | 12min | r | 18.33 | 0.02\n2025-06-12T22:36 | 12min | r | 18.29 | 0.04\n2025-06-12T23:54 | 4min | r | 18.35 | 0.03\n2025-06-13T00:46 | 8min | r | 18.36 | 0.03\n\nOn 2025-06-13 starting at 20:27 UT (23.85 hr after the trigger), we re-observed the object [VV2006] J131446.6+544804 with the spectro-imager MISTRAL. We obtained 1 minute of observation in r-band and measured a magnitude of r = 18.37 +/- 0.07, consistent with the T120 measurements on 2025-06-12. We also obtained 1 hour of spectroscopic observations using the MISTRAL blue mode with a spectral resolution of ~700 under moderately good conditions. When compared to the SDSS public spectrum, a preliminary analysis of the spectrum shows a flux increase of the Fe II complex between ~6600 AA and ~7000 AA. This increase is roughly consistent with the r-band magnitude variation observed by the T120 and MISTRAL.\n\nOur observations suggest that the Swift/XRT source #1 is the X-ray counterpart to [VV2006] J131446.6+544804 source, a known QSO at z~ 0.49. The X-ray detection of this source is the first reported to our knowledge and may indicate that the SVOM trigger is also associated with this event. This object being radio-quiet (2.9 mJy at 1.4GHz, NVSS) without typical lines of TDEs, and the observed r-band magnitudes being nearly constant after the initial increase suggest a likely association with an accretion event onto the central black hole of this QSO and would disfavor a GRB nature of this event. \n\nWe encourage further observations of [VV2006] J131446.6+544804.\n\nWe acknowledge the excellent support from Observatoire de Haute-Provence and in particular the students and professors from the summer camp OHP 2025 (Institut Origines) and the SOPHIE observer, Xavier Delfosse.\n",
  "eventId": "sb25061218",
  "version": 2,
  "bibcode": "2025GCN.40779....1A",
  "editedOn": 1750261795788,
  "submittedHow": "web",
  "createdOn": 1750258500251,
  "submitter": "Christophe Adami at LAM <christophe.adami@lam.fr>",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Christophe Adami at LAM <christophe.adami@lam.fr>",
  "circularId": 40779,
  "subject": "sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations",
  "format": "text/plain"
}