AstroNote 2024-102

We observed the field of the AT 2024ggi (ATLAS24fsk) (AstroNote 2024-100, Srivastav et al.) as part of the Kinder survey (Chen et al., AstroNote 2021-92). We used the 40cm-SLT at Lulin Observatory, Taiwan, to obtain images in u, g, r, i, and z filters sequentially. Observations started at 11:24 UT on 11 of April 2022 (MJD = 60411.476), 8.1 hours after the ATLAS discovery epoch. The images were taken under an average seeing conditions 2".2 and at an medium airmass of 2.3.

We used the Kinder pipeline (Yang et al. A&A 646, A22) to measure the PSF magnitudes of AT 2024ggi (all in the AB system) without template subtraction, as followed:

u = 17.09 +/- 0.25, 
g = 16.70 +/- 0.10,
r = 16.65 +/- 0.05, 
i = 16.68 +/- 0.05, and
z = 16.73 +/- 0.06 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).

Comparing with the ATLAS o-band discovery magnitude o=18.92, the r-band has been rising ~2.3 mag in 8.1 hours. The finder for AT 2024ggi is attached. We are still observing continuously in a high cadence.