The redshift distribution of Einstein Probe transients supports their relation to gamma-ray bursts

Brendan O'Connor; Paz Beniamini; Eleonora Troja; Malte Busmann; Simone Dichiara; Ramandeep Gill; Jonathan Granot; Michael Moss; Xander Hall; Antonella Palmese; Niccolo Passaleva; Yu-Han Yang

arXiv · 2509.07141

The redshift distribution of Einstein Probe transients supports their relation to gamma-ray bursts

Brendan O'Connor·Paz Beniamini·Eleonora Troja·Malte Busmann·Simone Dichiara·Ramandeep Gill·Jonathan Granot·Michael Moss·Xander Hall·Antonella Palmese·Niccolo Passaleva·Yu-Han Yang

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Abstract

The launch of the \textit{Einstein Probe} unleashed a new era of high-energy transient discovery in the largely unexplored soft X-ray band. The \textit{Einstein Probe} has detected a significant number of fast X-ray transients that display no gamma-ray emission, complicating their robust association to more common gamma-ray bursts. To explore their possible connection, we analyzed the redshift distribution of both \textit{Einstein Probe} fast X-ray transients and long duration gamma-ray bursts. A comparative analysis of their cumulative redshift distributions using non-parametric two-sample tests, namely the Kolmogorov-Smirnov and Anderson-Darling tests, finds no statistically significant difference. These tests favor that their redshifts are drawn from the same underlying distribution. This empirical connection between \textit{Einstein Probe} transients and long gamma-ray bursts is further supported by their agreement with the so-called ``Amati relation'' between the spectral peak energy and the isotropic-equivalent energy. Together, these results indicate that most extragalactic \textit{Einstein Probe} fast X-ray transients are closely related to long gamma-ray bursts and originate from a massive star (collapsar) progenitor channel. Our findings highlight the role of the \textit{Einstein Probe} in uncovering the missing population of failed jets and dirty fireballs that emit primarily at soft X-ray wavelengths.

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Brendan O'Connor, Paz Beniamini, Eleonora Troja, Malte Busmann, Simone Dichiara, Ramandeep Gill, Jonathan Granot, Michael Moss, Xander Hall, Antonella Palmese, Niccolo Passaleva, Yu-Han Yang. 2025-09-08. The redshift distribution of Einstein Probe transients supports their relation to gamma-ray bursts. https://arxiv.org/abs/2509.07141

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