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GCN Circular 36150

EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa
2024-04-17T18:13:16Z (a month ago)
S. Srivastav at Oxford <>
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S. Srivastav, J. H. Gillanders, L. Rhodes (Oxford), S. J. Smartt (Oxford/QUB), T.-W. Chen (NCU), M. Huber, K. C. Chambers (IfA), M. Fulton, K. W. Smith (QUB) report on behalf of a larger collaboration:

We report optical follow-up observations of AT2024gsa (Aryan et al., GCN 36094; Chen et al. TNS Astronomical Transient Report No. 207843), the candidate optical counterpart to the fast X-ray transient EP240414a (Lian et al., GCN 36091; Guan et al., GCN 36129). AT2024gsa was reported to be decaying in the optical (Xu et al., GCN 36105).

We observed AT2024gsa with the 1.8-m Pan-STARRS1 telescope in iz-bands on 2 epochs, with observations starting on MJDs 60416.4 and 60417.4, corresponding to ~2.0 and ~3.0 days post-discovery of the X-ray transient. Our PS1 photometry shows the transient has brightened from 22.2 +/- 0.3 (on MJD 60416.4) to 20.9 +/- 0.06 (on MJD 60417.4) in the i-band, suggesting a rise of ~1.3 mag/day.  A similar rise was also seen in the z-band.

Assuming AT2024gsa is associated with the potential host galaxy SDSS J124601.99-094309.3 at z=0.41 (Jonker et al., GCN 36110), the transient currently has an absolute rest-frame r-band magnitude of ~ -21. Further followup observations are encouraged.
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