Discovery and Extensive Follow-up of SN 2024ggi, a Nearby Type IIP Supernova in NGC 3621
T. W. Chen, S. Yang, Shubham Srivastav, Takashi J. Moriya, S. J. Smartt, S. Rest, A. Rest, Hsing Wen Lin, Hao-Yu Miao, Yu‐Chi Cheng, Amar Aryan, Chia-Yu 家羽 Cheng 鄭, M. Fraser, Li-Ching Huang, Meng-Han 孟翰 Lee 李, Cheng-Han 政翰 Lai 賴, Yu-Hsuan 宇軒 Liu 劉, A. K., K. Smith, H. F. Stevance, Ze-Ning 泽宁 Wang 王, J. P. Anderson, C. R. Angus, Thomas de Boer, K. C. Chambers, Hao-Yuan Duan, Nicolas Erasmus, M. Fulton, Hua Gao, Joanna Herman, Wei-Jie 偉傑 Hou 侯, Hsiang-Yao 翔耀 Hsiao 蕭, M. E. Huber, Chien-Cheng Lin, Hung-Chin Lin, E. A. Magnier, Ka Kit 家傑 Man 文, T. Moore, Chow‐Choong Ngeow, M. Nicholl, Po-Sheng Ou, G. Pignata, Yu‐Chien Shiau, Julian S. Sommer, J. Tonry, Xiaofeng Wang, R. J. Wainscoat, D. R. Young, You-Ting 祐廷 Yeh 葉, Jujia Zhang
Abstract
Abstract We present the discovery and early observations of the nearby Type II supernova (SN) 2024ggi in NGC 3621 at 6.64 ± 0.3 Mpc. The SN was caught <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.9</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> hr after its explosion by the ATLAS survey. Early-phase, high-cadence, and multiband photometric follow-up was performed by the Kilonova Finder (Kinder) project, collecting over 1000 photometric data points within 1 week. The combined o - and r -band light curves show a rapid rise of 3.3 mag in 13.7 hr, much faster than SN 2023ixf (another nearby and well-observed SN II). Between 13.8 and 18.8 hr after explosion, SN 2024ggi became bluer, with u − g color dropping from 0.53 to 0.15 mag. The rapid blueward evolution indicates a wind shock breakout (SBO) scenario. No hour-long brightening expected for the SBO from a bare stellar surface was detected during our observations. The classification spectrum, taken 17 hr after the SN explosion, shows flash features of high-ionization species such as Balmer lines, He i , C iii , and N iii . Detailed light-curve modeling provides critical insights into the circumstellar material (CSM). Our favored model has an explosion energy of 2 × 10 51 erg, a mass-loss rate of 10 −3 M ⊙ yr −1 (with an assumed 10 km s −1 wind), and a confined CSM radius of 6 × 10 14 cm. The corresponding CSM mass is 0.4 M ⊙ . Comparisons with SN 2023ixf highlight that SN 2024ggi has a less dense confined CSM, resulting in a faster rise and fainter UV flux. Citizen astronomer collaboration and extensive data are essential for SBO searches and detailed SN characterizations.