Following the notication of Srivastav et al. (AstroNote 2024-100), archival imaging from the Legacy survey suggests a well detected red source consistent at the position of SN 2024ggi (ATLAS24fsk). However, we found that the magnitude of this source was not reported in the Legacy survey catalogue. Therefore we queried Legacy survey images from www.legacysurvey.org with a resolution of 0.1 arcsecond per pixel, and used our Kinder pipeline (Yang et al. A&A 646, A22) to measure the PSF magnitudes (all in the AB system) as follows:
g = 23.04 +/- 0.37,
r = 23.01 +/- 0.24,
i = 22.73 +/- 0.13, and
z = 21.68 +/- 0.09 mag.
Our quoted magnitudes are calibrated against Skymapper field stars, and have not been corrected to account for the expected Galactic foreground extinction, which corresponds to a reddening of E_(B-V) = 0.07 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
As a double check, we measured other field stars (e.g. Objid: 15234, RA,Dec = 169.5933, -32.8385) whose magnitudes were measured by Legacy Survey themself, and obtained similar results in their catalogue.
With a host distance of 6.7 Mpc (m - M = 29.14) and NED Milky Way extinction corrections, we calculated its absolute magnitudes as g/r/i/z = -6.37/-6.31/-6.55/-7.56 mag. This is within the range typical for a red supergiant.
As noted in Srivastav et al. (AstroNote 2024-100), the source is resolved into two in the F814W band of HST archival images. However, we caution that they appear blended in the Legacy Survey images due to low resolution, consequently the reported magnitudes represent upper limits for the luminosity of the potential progenitor of SN 2024ggi.
| Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TNS | 2024ggi [ATLAS24fsk] | 11:18:22.091 | -32:50:15.29 | SN II | 0.002435 | 11:18:22.087 | -32:50:15.27 | SN II | 0.002435 |