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Einstein Probe detects mysterious X-ray transient that doesn't fit any known class

The Einstein Probe has detected a new X-ray transient designated EP260628c. This event was first identified by the Wide-field X-ray Telescope on June 28, 2026. The source does not fit any known class of cosmic explosion.

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What changed

The telescope has detected a new transient, EP260628c, following the previous identification of EP260623a.

Live updates

  1. Einstein Probe identifies new mysterious X-ray transient EP260628c

    The Einstein Probe has detected a new X-ray transient designated EP260628c. This event was first identified by the Wide-field X-ray Telescope on June 28, 2026. The source does not fit any known class of cosmic explosion.

    What's confirmed:

    • The Wide-field X-ray Telescope on the Einstein Probe mission detected X-ray transient EP260628c starting at 2026-06-28 16:22:49 UTC.
    • EP260628c is located at R.A. = 339.500 deg and Dec = 53.226 deg with a radius uncertainty of 2.7 arcmin.
    • The absorption-corrected 0.5-4 keV flux for EP260628c is 1.3 (+7.6/-0.6) x 10^-10 erg cm^-2 s^-1.
    • A previously detected source called EP240305a produced two brief X-ray flares separated by about 200 seconds of quiet.
    • Analysis of EP240305a was published in the journal Monthly Notices of the Royal Astronomical Society on June 13.

    Still unconfirmed:

    • EP260628c is located at low Galactic latitude l = 103.648, b = -4.576.
    • The 0.5-4 keV spectrum of EP260628c fits an absorbed power-law model with a photon index of 1.7 (+2.2/-1.6).
    confidence 90%

  2. Einstein Probe Detects Rare X-ray Transients

    The Einstein Probe has identified unusual X-ray transients that do not fit known astronomical classes. One event, EP260623a, was located 6.8 billion light-years away in Pegasus. Astronomers are investigating if these flashes result from intermediate-mass black holes destroying white dwarf stars.

    What's confirmed:

    • The Einstein Probe detected an X-ray transient that does not fit any known class.
    • X-ray transient EP260623a was detected on June 23, 2026, at a distance of 6.8 billion light-years in Pegasus.
    • The Einstein Probe is a Chinese space telescope.

    Still unconfirmed:

    • The event may have been an intermediate-mass black hole ripping apart and devouring a dense white dwarf star.
    • Indian astronomers from the Indian Institute of Astrophysics may have revealed the origin of these flashes.
    • The Einstein Probe detected a transient designated EP260530a on May 30, 2026.
    • A transient designated EP240305a showed rapid X-ray fading and lingering radio signals.
    confidence 80%