Jacobson-Galán, W. V. and Davis, K. W. and Kilpatrick, C. D. and Dessart, L. and Margutti, R. and Chornock, R. and Foley, R. J. and Arunachalam, P. and Auchettl, K. and Bom, C. R. and Cartier, R. and Coulter, D. A. and Dimitriadis, G. and Dickinson, D. and Drout, M. R. and Gagliano, A. T. and Gall, C. and Garretson, B. and Izzo, L. and LeBaron, N. and Miao, H. Y. and Milisavljevic, D. and Rest, A. and Rojas-Bravo, C. and Santos, A. and Sears, H. and Subrayan, B. M. and Taggart, K. and Tinyanont, S. (2024) SN 2024ggi in NGC 3621 : Rising Ionization in a Nearby, Circumstellar-material-interacting Type II Supernova. Astrophysical Journal, 972 (2): 177. ISSN 0004-637X
Full text not available from this repository.Abstract
We present UV-optical-near-infrared observations and modeling of supernova (SN) 2024ggi, a type II supernova (SN II) located in NGC 3621 at 7.2 Mpc. Early-time (“flash”) spectroscopy of SN 2024ggi within +0.8 days of discovery shows emission lines of H i, He i, C iii, and N iii with a narrow core and broad, symmetric wings (i.e., “IIn-like”) arising from the photoionized, optically thick, unshocked circumstellar material (CSM) that surrounded the progenitor star at shock breakout (SBO). By the next spectral epoch at +1.5 days, SN 2024ggi showed a rise in ionization as emission lines of He ii, C iv, N iv/v, and O v became visible. This phenomenon is temporally consistent with a blueward shift in the UV-optical colors, both likely the result of SBO in an extended, dense CSM. The IIn-like features in SN 2024ggi persist on a timescale of t IIn = 3.8 ± 1.6 days, at which time a reduction in CSM density allows the detection of Doppler-broadened features from the fastest SN material. SN 2024ggi has peak UV-optical absolute magnitudes of M w2 = −18.7 mag and M g = −18.1 mag, respectively, that are consistent with the known population of CSM-interacting SNe II. Comparison of SN 2024ggi with a grid of radiation hydrodynamics and non-local thermodynamic equilibrium radiative-transfer simulations suggests a progenitor mass-loss rate of M ̇ = 10 − 2 M ⊙ yr−1 (v w = 50 km s−1), confined to a distance of r < 5 × 1014 cm. Assuming a wind velocity of v w = 50 km s−1, the progenitor star underwent an enhanced mass-loss episode in the last ∼3 yr before explosion.