EP260321a

General information

EP260321a is an Einstein Probe WXT-detected soft X-ray transient with an EP/FXT refined position, followed by identification of an optical transient in the error circle that was spectroscopically classified as the broad-lined Type Ic supernova SN 2026gzf in a z≈0.0343 host galaxy.

Wavelength coverage

X-ray: EP/WXT detection and refined analysis; EP/FXT autonomous follow-up with fading light curve; later Chandra non-detection.
Optical: Multiple imaging campaigns (Kinder/LOT, MASTER, LCO, VLT/FORS2 imaging, GOTO, ZTF, TRT, TNT, DFOT) and spectroscopy (VLT/MUSE, VLT/X-shooter, VLT/FORS2, Gemini/GMOS, Mondy/ADAM) establishing a Type Ic-BL SN.
Near-IR: J-band detections (SYSU; JinShan 100C) and later J/K photometry (SAI ASTRONIRCAM).
Radio: uGMRT and ATCA non-detections; VLA early non-detections followed by a reported marginal detection at ~13.6 d and later non-varying re-observation.
Neutrinos: IceCube search reported no significant coincidence and provided an upper limit. Bands with no observations mentioned: gamma-ray, UV, sub-mm/mm, gravitational waves.

Lightcurve and spectrum

Redshift

z = 0.0343 (Spectroscopy (host emission lines; also narrow Ca II absorption reported))
z=0.0343 from VLT/MUSE emission lines; consistent with Gemini/GMOS and Mondy/ADAM host lines. X-shooter reports narrow Ca II absorption at z=0.0344; a nearby 2dFGRS galaxy at z=0.0345 was also noted in the EP region.

What’s special vs typical

GCN 44412: EP260321a/SN 2026gzf: spectroscopy at Mondy observatory

2026-04-27T15:01:46.982Z | rev 0

GCN 44403: EP260321a: Upper limits from ATCA radio observations

2026-04-23T17:14:05.809Z | rev 0

GCN 44357: EP260321a: VLA radio follow-up

2026-04-20T21:56:06.479Z | rev 0

GCN 44348: EP260321A/AT2026gzf: Optical observation from 1.3m DFOT

2026-04-19T09:06:27.920Z | rev 0

GCN 44295: EP260321a: CMO SAI J,K observations

2026-04-14T11:27:29.301Z | rev 0

GCN 44250: EP260321a: Chandra X-ray Non-detection

2026-04-09T22:11:06.550Z | rev 0

GCN 44239: EP260321a: VLA radio detection

2026-04-09T01:06:49.838Z | rev 0

GCN 44229: EP260321a: Upper limits from VLA radio observations

2026-04-07T14:50:36.772Z | rev 0

GCN 44227: EP260321a: uGMRT observations

2026-04-07T11:11:53.694Z | rev 0

GCN 44171: EP260321a :Xinglong optical observations

2026-04-01T05:05:57.078Z | rev 0

GCN 44117: EP260321a: JinShan near-infrared observations

2026-03-26T07:29:39.155Z | rev 2

GCN 44117: EP260321a: JinShan near-infrared observations

2026-03-26T07:29:39.155Z | rev 0

GCN 44114: EP260321a: Upper limits from a neutrino search with IceCube

2026-03-25T21:30:19.883Z | rev 0

GCN 44110: EP260321a: J-band observations by the SYSU 80 cm infrared telescope

2026-03-25T09:38:42.261Z | rev 0

GCN 44108: EP260321a: Gemini-South confirmation of a supernova

2026-03-24T18:32:10.884Z | rev 0

GCN 44108: EP260321a: Gemini-South confirmation of a supernova (duplicate submission)

2026-03-24T18:32:10.884Z | rev 2

GCN 44107: EP260321a: Gemini-South confirmation of a supernova

2026-03-24T18:32:10.460Z | rev 0

GCN 44105: EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf

2026-03-24T15:23:31.199Z | rev 0

GCN 44103: EP260321A: Mondy optical observations

2026-03-24T12:34:33.163Z | rev 0

GCN 44092: EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344

2026-03-23T17:12:25.137Z | rev 2

GCN 44092: EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344

2026-03-23T17:12:25.137Z | rev 0

GCN 44091: EP260321a: COLIBRÍ further optical observations and brightening

2026-03-23T16:06:10.120Z | rev 0

GCN 44089: EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate

2026-03-23T15:36:09.742Z | rev 0

GCN 44087: EP260321a: Early TRT rising followed by JinShan decaying and then re-rising

2026-03-23T11:26:51.737Z | rev 0

GCN 44084: EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a

2026-03-22T23:06:20.415Z | rev 0

GCN 44083: EP260321a: GOTO detection of blue variable source

2026-03-22T21:30:52.151Z | rev 0

GCN 44082: EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343

2026-03-22T19:50:53.722Z | rev 0

GCN 44081: EP260321a: further Kinder optical observations

2026-03-22T15:49:58.896Z | rev 0

GCN 44079: EP260321a: Las Cumbres upper limit

2026-03-22T13:12:22.886Z | rev 0

GCN 44076: EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission

2026-03-22T07:01:20.258Z | rev 0

GCN 44075: EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate

2026-03-22T04:32:32.742Z | rev 0

GCN 44070: EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle

2026-03-21T17:18:54.161Z | rev 0

GCN 44069: EP260321a: Global MASTER-Net observations report

2026-03-21T13:54:25.847Z | rev 0

GCN 44068: EP260321a: Einstein Probe detection of an X-ray transient

2026-03-21T13:01:43.196Z | rev 0