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GCN Circular 36110

X-ray transient EP 240414a - GTC spectroscopic observations
2024-04-15T09:47:43Z (a month ago)
Andrew Levan at Radboud University <>
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P.G. Jonker (Radboud), A.J. Levan (Radboud), D.B. Malesani (Radboud/DAWN NBI), N.R. Tanvir (Leicester), D. Garcia (IAC), A de Ugarte Postigo (CNRS, OCA, LAM) report for a larger collaboration: 

We obtained spectroscopic observations of the counterpart and candidate host galaxy of EP 240414a (Lian et al.,. GCN 36091; Aryan et al., GCN 36094; Xu et al., GCN 36105) with the GTC telescope equipped with the OSIRIS+ instrument. Observations began at 00:46 UT on April 15, approximately 15 hr after the transient onset. 4x1200 s of exposures were obtained with the slit oriented through both the nucleus of the candidate host galaxy SDSS J124601.99-094309.3 and the counterpart (Aryan et al., GCN 36094). 

SDSS J124601.99-094309.3 shows strong emission lines from hydrogen and oxygen with a common redshift of z = 0.41, somewhat higher than the photometric redshift. The trace from the transient, which has a lower S/N, is featureless in our preliminary reduction, and as such we cannot place strong constraints on its association with SDSS J124601.99-094309.3. The offset of the source at z = 0.41 corresponds to approximately 25 kpc in projection, which would be a large offset for a core-collapse event, although we note that the H-alpha line is extended to within ~1” of the transient location. If associated with a supernova similar to 1998bw at z = 0.41, we would expect a peak at around R ~ 22.5 mag approximately 3 weeks from now. 

We thank the GTC staff for the rapid execution of these observations. 

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