EP-FXT detection of the FBOT candidate AT2024qfm
ATel #16757; Y. F. Liang, B. Wang (PMO, CAS), D. Y. Li, Y. L. Wang, W. X. Wang, H. W. Pan, H. Sun, J. W. Hu (NAOC, CAS), Y. Li, J. J. Geng, D. Xiao, X. F. Wu (PMO, CAS), Z. G. Dai (USTC), L. Li (NCU), A. Li (BNU), Y. Chen, S. M. Jia (IHEP, CAS), on behalf of the Einstein Probe team
on 7 Aug 2024; 11:19 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Transient
We report on the detetction of the X-ray emission of the FBOT candidate AT2024qfm (M. Fulton et al., Astro Note 2024-206) by the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The EP-FXT observation was carried out at 2024-08-04T00:52:31 (UTC), about 8 days after the first optical detection, with an exposure time of 6600 seconds. An X-ray source was detected at the position of AT2024qfm. The X-ray spectrum can be fitted by an absorbed power-law with a photon index of 2.5(+/-0.8), and the absorption fixed at the Galactic value of 4.7 x 10^20 cm^-2. The derived unabsorbed 0.5-10 keV flux is 6.9(-2.3/+6.3) x 10^-14 erg/s/cm^2, which has decreased compared to the Swift-XRT flux (R. Margutti et al., ATel#16748). With the SDSS photometric redshift of z = 0.227 (Gillanders et al., AstroNote 2024-210), the corresponding X-ray luminosity is ~1 x 10^43 erg/s. After few days of the peak, the AT2024qfm was still more luminous than the prototype FBOT event AT2018cow.
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).
