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The Astronomer's Telegram                   http://www.astronomerstelegram.org

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ATEL #16584							    ATEL #16584

Title:	EP240408A: Einstein Probe FXT observations
Author:	N. Rea, F. Coti Zelati, A. Marino (ICE-CSIC, IEEC), E. Kuulkers
		(ESA), Y. Chen, S. M. Jia, C. K. Li, W. W. Cui, H. Feng, J. Guan,
		D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song,  L. Tao, J. Wang,
		J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS),
		J. W. Hu, C. C. Jin, D. Y. Li, Z. X. Ling, H. Y. Liu, Y. Liu, H. Sun,
		W. Yuan, C. Zhang, D. H. Zhao (NAOC, CAS), P. G. Jonker (RU, SRON),
		A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra,
		A. Rau, P. Friedrich, N. Meidinger, V. Burwitz (MPE), B. Cordier (CEA)
		on behalf of the Einstein Probe team
Queries:	rea@ice.csic.es
Posted:	12 Apr 2024; 15:31 UT
Subjects:X-ray, Request for Observations

The X-ray transient EP240408A (Hu et al. GCN #36053), discovered by the
Einstein Probe (EP) Wide-field X-ray Telescope (WXT) on 2024-04-08T17:56:30
(UTC) was observed by the EP Follow-up X-ray Telescope (FXT) in full frame
mode starting on 2024-04-10T12:35:09 (UTC) for an on source time of ~24
ks over an elapsed time of ~49 ks. 

The unidentified X-ray source detected by Swift XRT on 2024-04-10 (Hu et
al. GCN#36057) and consistent with the WXT position of EP240408A has been
detected by EP-FXT at a net count rate of ~2.1 cts/s (0.5-10 keV; summing
up the two detectors). The X-ray spectrum is well modeled by an absorbed
power law with hydrogen column density NH=(1.18+/-0.01)e21 cm-2 and photon
index Gamma=2.21+/-0.03. The observed flux is ~1.5e-11 erg/cm2/s (0.5-10
keV). The lightcurve shows variability and a decline in the net count rate
from ~2.35 cts/s to ~2.0 cts/s over a time span of ~49 ks. The source is
not detected in past eROSITA observations of the field, with a flux upper
limit of <6e-14 erg/cm2/s (0.2-2.3 keV). This is a factor of ~300 lower
than the flux measured with EP-FXT. Multi-band observations are encouraged.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor
the soft X-ray sky with 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, aimed at enhancing
our understanding of transient phenomena across the electromagnetic spectrum.

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