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GCN Circular 36859

Subject
GRB240713A: X-ray follow-up observation with EP-FXT
Date
2024-07-14T09:10:52Z (4 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
J. Yang (NJU), Q. Y. Wu, M. J. Liu, X. Pan, Z. X. Ling, C. C. Jin, W. Yuan, Y. Liu, C. Zhang, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, S. X. Wen, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Guan, C. K. Li, Y. Chen, S. M. Jia, W. W. Cui, H. Feng, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team

Following the detection of the GRB 240713A reported by ECLAIRs on board SVOM (Schanne et al., GCN 36854Not found
 
 
), which also shows a possible sub-threshold signal in Fermi/GBM data (Burns et al., GCN 36856Not found
 
 
), we performed an observation of GRB 240713A with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2024-07-13T15:23:28 (UTC), about 13.3 hours after the detection of SVOM/ECLAIRs. The exposure time is about 6.8 ks. Through the preliminary analysis of the EP-FXT data, we found 10 X-ray sources within the SVOM/ECLAIRs localization error box (10 arcmin centered on RA, Dec = 352.59, 1.88), which are detailed as follows. The positions are given with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). The 0.5 - 10 keV flux is derived from the FXT-B data if the source is detected by both FXT-A and FXT-B.

Source | R.A. | Dec. | FXT-A Significance | FXT-B Significance | Estimated Flux 
       |      |      |                    |                    |   (erg/s/cm^2) 
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EP J233058.2+015317  | 352.7425 | 1.8879 | 7.4 | 8.7 | 5.6 x 10^-14
EP J233023.3+015537* | 352.5970 | 1.9269 | 4.7 | 6.1 | 4.5 x 10^-14
EP J233039.0+014426* | 352.6627 | 1.7404 | 4.1 | 5.3 | 4.5 x 10^-14
EP J233020.4+015231  | 352.5850 | 1.8753 | 5.1 | 5.0 | 2.7 x 10^-14
EP J233016.5+020124  | 352.5687 | 2.0232 | 4.9 | 4.6 | 3.0 x 10^-14
EP J233017.4+014339  | 352.5724 | 1.7275 | <3.0 | 4.1 | 4.4 x 10^-14
EP J233012.2+015001  | 352.5509 | 1.8335 | <3.0 | 3.6 | 2.1 x 10^-14
EP J233042.1+015623  | 352.6754 | 1.9397 | <3.0 | 3.6 | 1.9 x 10^-14
EP J233002.5+015949  | 352.5104 | 1.9968 | 4.1 | <3.0 | 2.5 x 10^-14
EP J232954.2+015030  | 352.4757 | 1.8416 | 4.7 | <3.0 | 2.4 x 10^-14
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*Note: EP J233023.3+015537 is 15.9 arcsec away from a quasar named SDSS J233022.43+015527.2, and EP J233039.0+014426 is 5.0 arcsec away from another quasar SDSS J233038.79+014428.6. These two sources may be related to the two quasars.

The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.