TITLE: GCN CIRCULAR NUMBER: 42714 SUBJECT: LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations DATE: 25/11/17 09:58:25 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Q. Y. Wu, J. W. Hu, Y. Liu (NAO, CAS), B. Zhang (HKU) on behalf of the Einstein Probe (EP) team: EP-FXT performed a series of follow-up observations of the LIGO/Virgo/KAGRA gravitational-wave event S251112cm (GCN 42650, GCN 42690), with 100 galaxy-targeted observations have been completed. These observations were conducted from 2025-11-12T15:38:36 to 2025-11-14T10:28:28 (UTC), with each pointing having an exposure of approximately 300 s. EP-FXT covered 88 deg2 (8.9% in probability) of the updated sky localization area (GCN 42690) We cross-matched all FXT detections from these pointings against the updated list of NED galaxies provided in GCN 42693, using a 100″ matching radius (for a galaxy at 100 Mpc this corresponds to an offset of ~50 kpc). Most matched sources have prior X-ray detections with FXT fluxes comparable to historical values. There are two weak sources without prior X-ray counterparts within the FXT error region. Their information is summarized below (RA/Dec in degrees with 10" error radius (90% C.L.); fluxes are the observed ones in 0.5–10 keV): Name | RA | Dec | Matched NED Galaxy | Sep. (arcsec) | Flux (erg/s/cm^2) | SNR ---------------------------------------------------------------------------------------------------------------------------- EPF_J234847.8-282639 | 357.1990 | -28.4442 | WISEA J234841.30-282641.1 | 85.2 | 7.4e-13| 6.6 EPF_J010845.7-463304 | 17.1904 | -46.5512 | SMDG J0108452-463428 | 83.8 | 1.4e-13| 4.2 In addition, FXT detected 8 sources with no prior X-ray detections, no matches to the NED galaxies and no obvious AGN or stellar counterparts within the FXT error regions. Their information is summarized below (RA/Dec in degrees with 10" error radius (90% C.L.); fluxes are the observed ones in 0.5–10 keV): Name | RA | Dec | Flux (erg/s/cm^2) | SNR ------------------------------------------------------------------------- EPF_J000245.6-341925 | 0.6899 | -34.3235 | 2.0e-13| 4.0 EPF_J020544.2-520424 | 31.4343 | -52.0734 | 1.7e-13| 4.1 EPF_J092041.9-081815 | 140.1746 | -8.3041 | 2.1e-13| 4.9 EPF_J093255.2-020027 | 143.2301 | -2.0076 | 4.3e-13| 3.5 EPF_J111043.0+362227 | 167.6792 | 36.3742 | 1.6e-13| 4.6 EPF_J113825.2+432218 | 174.6051 | 43.3716 | 7.3e-14| 5.4 EPF_J232328.1-114600 | 350.8670 | -11.7667 | 1.5e-13| 3.9 EPF_J234628.3-290057 | 356.6177 | -29.0158 | 7.9e-13| 4.5 Further FXT observations of these candidates will be conducted. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/42714. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...