A handful of astronomers have now identified the first well-observed fast X-ray transient (FXT), EP241107a, detected on November 7, 2024. The discovery was made using the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe, a Chinese space telescope launched earlier in January 2024. This momentous detection has answered many questions while raising new ones about the origins and nature of this cosmic phenomenon.
Clearly showed an exceptional X-ray luminosity of ∼3.4 quindecillion erg/s (0.5–4 keV band). Unlike most astrophysical transients, this powerful burst lasted only from several hundred seconds to several hours. Its importance alone would make it an exciting event in the world of astrophysics. Approximately 60 minutes after the initial detection of EP241107a, an X-ray afterglow was observed. This afterglow had a low luminosity of 0.012 quindecillion erg/s in the 0.5–10 keV band.
EP241107a has spectroscopically been measured with a redshift of 0.457 by astronomers. This vital data allows them to research the distance and expansion of the universe. Researchers found an optical counterpart in the Ic-band. Its magnitude is 17.85, a rather abstract number but one that offers important information about the event’s scale and distribution. Our team was able to detect a radio counterpart at both frequencies of observation, 10 GHz and 6 GHz. The resulting flux densities of ∼232 and ∼207 micro-Jy were measured.
The host galaxy of EP241107a indeed has an awe-inspiring stellar mass, estimated at about two billion solar masses! It’s has a relatively high star formation rate of around 0.6 solar masses per year. This means that the environment around EP241107a is perfectly suited for energetically favorable processes. Without the right measures in place, these processes can lead to explosive flash fires.
The research team, headed by Deepak Eappachen at Indian Institute of Astrophysics in Bengaluru, India, made multi-wavelength observations. Here, their observations combined provide the strongest evidence yet that EP241107a was likely produced from an erupting gamma-ray burst. They posted the results from their extensive observational campaign on the arXiv preprint server on November 4th. This occurred only a few days before the official discovery of the transient.
Finding both the optical and radio counterparts for EP241107a greatly increases our understanding of this FXT. This finding is exciting not only for its immediate discovery, but for its future astronomical potential. Just like the research community, they’re all looking forward to further investigations. They hope these studies will help uncover the excitation mechanisms of these violent cosmic events and their importance in the larger field of astrophysics.