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GCN Circular 35932

X-ray transient EP240315a: ATLAS detection of a possible optical counterpart AT2024eju
2024-03-16T22:08:06Z (2 months ago)
S. Srivastav at Oxford <>
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S. Srivastav, S. J. Smartt (Oxford), M. D. Fulton, K. W. Smith, A. Aamer, C. R. Angus, M. McCollum, T. Moore, M. Nicholl, X. Sheng, J. Weston, D. R. Young (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), A. Andersson, J. H. Gillanders, L. Rhodes, H. Stevance (Oxford), J. Sommer (LMU/QUB), L. Denneau, J. Tonry, H. Weiland, A. Lawrence, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard):

Here we report the ATLAS detection of an optical transient AT2024eju, discovered within the error circle of the fast X-ray transient EP240315a reported by the Einstein Probe mission (Zhang et al, GCN 35931). 

ATLAS is a quadruple 0.5-m telescope system with two units in Hawaii, one in Chile and one in South Africa (see Tonry et al. 2018, PASP, 130:064505), routinely surveying the visible sky on a daily basis. We promptly process all data with our transient science server (Smith et al. 2020, PASP, 132:085002).

ATLAS detected AT2024eju (TNS Astronomical Transient Report No. 205383) during normal survey mode observations at an AB magnitude of 19.37 +/- 0.14 in the ATLAS-cyan band on MJD 60384.887, around 1.1 hrs following the detection of the X-ray transient. The position of AT2024eju is 0.8 arcmin offset from the coordinates reported by Zhang et al. We found no historical detections of any excess optical flux in ATLAS at this position through forced photometry.

Spectroscopic classification of this transient is encouraged.
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