GCN Circular 46153
Subject
EP261015a/SN 2026ahoa: MMT optical counterpart detection
Event
Date
2026-11-04T23:04:55Z (8 hours ago)
From
piramonkumnurdmanee2031@u.northwestern.edu
Via
Web form
P. Kumnurdmanee, G. Srinivasaragavan and W. Fong (Northwestern) report:
We observed the location of EP261015a (Li et al., GCN 45956) and its optical counterpart (Corcoran et al., GCN 45955; Moreno Méndez et al., GCN 45960; Fortin et al., GCN 45991; Volnova et al., GCN 45997; Pawar et al., GCN 45998; Shivaprasad et al., GCN 46000; Pankov et al., GCN 46003; Gou et al., GCN 46009; Burkhonov et al., GCN 46017; Izzo GCN 46021) with the Binospec instrument mounted on the MMT 6.5-meter telescope atop Mount Hopkins, Arizona. We obtained 10x120-sec imaging in the r-band under Program UAO-G319-26B (PI: Srinivasaragavan) starting on 2026-11-03 06:21 UTC (18.7 days after the beginning of the EP/WXT light curve).
We perform image subtraction with HOTPANTS against the archival r-band Legacy Survey image, and clearly detect the optical counterpart SN 2026ahoa (Martin-Carrillo et al., GCN 46131). We measure an apparent brightness from the residual image of r = 21.56 +/- 0.03 (AB), not corrected for Galactic extinction demonstrating continued brightening relative to the most recent observations in the same band (Izzo et al., GCN 46021). We note that at the redshift of z=0.31 (Martin-Carrillo et al., GCN 46131), SN 2026ahoa has an absolute magnitude of M_r ~ -19.4 at a rest-frame time of 14.3 days, comparable to the R-band absolute magnitude of SN 1998bw at a similar rest-frame time. We further measure the offset of the SN from the host galaxy center to be moderate, 3.8 +/- 0.3 kpc at z=0.31, incorporating astrometric tie, transient and host positional uncertainties.
We thank the MMT queue observer Ryan Howie and scheduler Ben Weiner for the rapid scheduling and execution of these observations.