GCN 45255: The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
2026-07-30T03:20:46.425Z | rev 0
H.Y. Ren (NAO, CAS), Y. F. Liang (PMO), J. W. Hu, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team:
The EP-WXT trigger 01709277130 (EP260729a, GCN 45253) at the time of 2026-07-29T17:04:47, is likely a stellar flare associated with RX J2350.0+2659 and also confirmed by optical observation (Jelinek et al., GCN 45254).
The refined analysis of the WXT data shows that the average WXT 0.5-4 keV spectrum can be fitted with an apec model. The best-fit temperature is 2.78 keV. The derived average unabsorbed 0.5-4 keV flux is 9.42 (-3.00/+7.95)×10^-11 erg/s/cm^2, corresponding to a luminosity of 1.24 (-0.45/+1.03)×10^31 erg/s.
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).
GCN 45254: EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
2026-07-29T22:52:45.612Z | rev 0
M. Jelinek, J. Strobl, F. Novotny and R. Hudec (ASU CAS Ondrejov) report:
We observed the position of the Einstein Probe transient EP260729a (Zhou et
al., GCN 45253) with the D50 telescope of the Astronomical Institute
Ondrejov, near Prague, Czech Republic, obtaining 19x120s r'-band exposures
starting at 21:13 UT on 2026 July 29 (~4.1 h after the WXT trigger).
We find no uncatalogued object in the error circle down to r>21.5 (3-sigma)
in the combined image.
The M4.0V high proper motion star RX J2350.0+2659 (ATLAS-RefCat2 r=13.876;
Zhou et al., GCN 45253) is bright and well detected in single exposures. It
appears elevated in brightness at the start of our sequence, fading over
~40 minutes. A linear fit gives an initial excess of ~0.14 mag over its
catalogued magnitude, decaying at ~0.1 mag/hour.
This fading excess supports the stellar flare origin of EP260729a suggested
by the EP team (Zhou et al., GCN 45253).
GCN 45253: EP260729a: Einstein Probe detection of an X-ray transient
2026-07-29T18:01:14.752Z | rev 3
H. Zhou (PMO, CAS), G. J. Yang, J. W. Hu, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260729a. The transient triggered EP-WXT (ID: 01709277130) at 2026-07-29T17:04:47 (UTC). The WXT position of the source is R.A. = 357.559 deg, DEC = 26.992 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 357.5308 deg, DEC = 26.9981 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
Please note that an M4.0V C-type star, RX J2350.0+2659 (High Proper Motion Star), exists within the FXT error circle. Due to limited data, we cannot rule out the possibility that WXT was triggered by a stellar flare from RX J2350.0+2659.
Further information will be updated when the telemetry data is received.
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).
GCN 45253: EP260729a: Einstein Probe detection of an X-ray transient
2026-07-29T18:01:14.752Z | rev 3
H. Zhou (PMO, CAS), G. J. Yang, J. W. Hu, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260729a. The transient triggered EP-WXT (ID: 01709277130) at 2026-07-29T17:04:47 (UTC). The WXT position of the source is R.A. = 357.559 deg, DEC = 26.992 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 357.5308 deg, DEC = 26.9981 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
Please note that an M4.0V C-type star, RX J2350.0+2659 (High Proper Motion Star), exists within the FXT error circle. Due to limited data, we cannot rule out the possibility that WXT was triggered by a stellar flare from RX J2350.0+2659.
Further information will be updated when the telemetry data is received.
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).
GCN 45253: EP260729a: Einstein Probe detection of an X-ray transient
2026-07-29T18:01:14.752Z | rev 3
H. Zhou (PMO, CAS), G. J. Yang, J. W. Hu, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260729a. The transient triggered EP-WXT (ID: 01709277130) at 2026-07-29T17:04:47 (UTC). The WXT position of the source is R.A. = 357.559 deg, DEC = 26.992 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 357.5308 deg, DEC = 26.9981 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
Please note that an M4.0V C-type star, RX J2350.0+2659 (High Proper Motion Star), exists within the FXT error circle. Due to limited data, we cannot rule out the possibility that WXT was triggered by a stellar flare from RX J2350.0+2659.
Further information will be updated when the telemetry data is received.
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).