TITLE: GCN CIRCULAR NUMBER: 39270 SUBJECT: EP250207b: Gemini GMOS-N z-band observations DATE: 25/02/10 17:04:14 GMT FROM: P.G. Jonker at Radboud University p.jonker@astro.ru.nl
Daniele B. Malesani (DAWN/ NBI and Radboud), Andrew J. Levan (Radboud), Jonathan Quirola-Vásquez (Radboud), Peter G. Jonker (Radboud), Javi Sánchez-Sierras (Radboud), Franz Bauer (PUC) report on behalf of a larger collaboration:
We obtained photometric observations of the field of the fast X-ray transient EP250207b discovered by Einstein Probe (Zhou et al., GCN 39266) with the GMOS instrument mounted on the Gemini-North telescope (PI: F. Bauer; program GN-2024B-FT-112). We obtained 6 images with 15 s exposure time each and 6 with an exposure time of 60 s each in the z-band filter beginning at 2025-02-10 10:40 UT, approximately 2.5 days after the EP/WXT trigger.
Within the EP/FXT error circle, comparing our stacked image with Legacy archival images we detect no plausible optical counterpart down to the depth of the Legacy Survey observations. Image subtraction between the GMOS and the Legacy Survey data also reveals no new sources.
We do note the presence of a bright galaxy within the FXT error circle. This galaxy lies at
RA(J2000) = 11:10:02.67 DEC(J2000) = -07:52:12.0
and has an r-band magnitude of r = 17.2. The galaxy is detected but WISE but it is not in ALLWISEAGN, implying it is unlikely to be an AGN. Following the prescription of Bloom et al. 2002 (doi: https://link.springer.com/article/10.1007/s41114-019-0024-0) we find a probability of 0.5% of such a galaxy lying within the FXT error circle by chance. The galaxy has a photometric redshift of z = 0.074+-0.009 from Legacy Survey (Zhou et al. 2021, doi:10.1093/mnras/staa3764).
We thank the staff of Gemini for their excellent support in securing these observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/39270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...