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GCN Circular 36567

LXT 240528A: LEIA detection of a fast X-ray transient
2024-05-29T17:53:09Z (15 days ago)
EP Team at NAOC/CAS <>
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T. Y. Lian, Z. X. Ling, D. Y. Li, H. Sun, H. Q. Cheng, H. Y. Liu, W. D. Zhang, Q. Y. Wu, C. C. Jin, Y. Liu , C. Zhang , W. Chen , C. Z. Cui , D. W. Fan , H. B. Hu , J. W. Hu , M. H. Huang , M. J. Liu , Z. Z. Lv,  X. Mao , H. W. Pan , X. Pan , W. X. Wang , Y. L. Wang , X. P. Xu , Y. F. Xu , H. N. Yang , M. Zhang , W. J. Zhang, D. H. Zhao (NAOC, CAS), D. M. Li, Q. X. Li (BNU),C. Y. Wang, Y. J. Zhang (THU), and W. Yuan (NAOC, CAS) on behalf of the LEIA and Einstein Probe team

We report on a fast X-ray transient LXT 240528A detected by LEIA (Lobster Eye Imager for Astronomy) in 0.5-4 keV. The position of the source is R.A. = 242.233 deg, DEC = 24.314 deg with an uncertainty of 1.7 arcmin (radius, 90%C.L. statistical and systematic). The source was detected by LEIA at 2024-05-28T12:27:14 (UTC). The averaged 0.5-4 keV spectrum can be fitted with an absorbed power law (with the column density fixed to the Galactic value of 6.2e+20 cm-2 with a photon index of 1.2(-/+0.3), giving an unabsorbed flux of 4.8(-0.8/+1.0)e-10 erg/s/cm2 in the 0.5-4 keV band. For a free column density, the best-fit photon index is 3.0(-0.8/+0.9), and the best-fit column density is 6.4(-0.2/+0.3)e+21 cm-2. The parameter error is within 1 sigma. The transient event lasted for approximately 200 seconds with a peak absorbed flux of ~1.5e-9 erg/s/cm2 in 0.5-4 keV band.

No previously known bright X-ray sources are found within the error circle around the source position. More follow-up observations are encouraged to help explore the nature of this transient.

LEIA (Zhang et al. 2022, ApJL, 941, 2; Ling et al. 2023, RAA, 23, 095007) is a soft X-ray Lobster-eye imager (0.5 - 4.0keV) with a FoV of 340 square degrees aboard the experimental satellite SATech-01 of the CAS, launched on July 27, 2022. The above result is preliminary and the final result will be published elsewhere.
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