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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 Hi, Hei, Ciii, and Niiiwith 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 Heii, Civ, Niv/v, and Ovbecame 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 oftIIn= 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 ofMw2= −18.7 mag andMg= −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 yr−1(vw= 50 km s−1), confined to a distance ofr< 5 × 1014cm. Assuming a wind velocity ofvw= 50 km s−1, the progenitor star underwent an enhanced mass-loss episode in the last ∼3 yr before explosion.
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This content will become publicly available on January 30, 2027
JWST Observations of SN 2024ggi. II. NIRSpec Spectroscopy and CO Modeling at +285–385 Days past the Explosion
Abstract We present James Webb Space Telescope (JWST) Near-Infrared Spectrograph observations of SN 2024ggi, spanning wavelengths of 1.7–5.5μm at +285.51 and +385.27 days postexplosion. These nebular spectra are dominated by asymmetric emission lines from atomic species including H, Ca, Ar, C, Mg, Ni, Co, and Fe, indicative of an aspherical explosion. The other strong features are molecular CO vibrational bands from the fundamental and first overtone. We introduce a novel, data-driven approach using non–local thermodynamic equilibrium three-dimensional (3D) radiative transfer simulations to model the CO emission with high fidelity. This method enables us to constrain the 3D CO distribution and its radial temperature structure. CO formation is found to occur prior to day +285, with subsequent evolution characterized by progressive evaporation. The CO mass decreases from approximately 8.7 to 1.3 ×10−3M⊙, while the average temperature drops from ≈2900 to ≈2500 K. Concurrently, the CO distribution transitions from nearly homogeneous to highly clumped (density contrast increasing fromfc≈ 1.2 to 2). The minimum velocity of the CO-emitting region remains nearly constant (v1≈ 1200 to 1100 km s−1), significantly above the receding photosphere velocity (vph≈ 500 km s−1), suggesting the photosphere resides within Si-rich layers. However, the temperature profile indicates that only a narrow zone reaches the conditions necessary for SiO formation. Due to a lack of observational constraints, SiO clumping is not modeled, and thus, synthetic SiO profiles for mass estimates are not highlighted. We discuss the implications of these findings for dust formation processes in SN 2024ggi.
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- Award ID(s):
- 2306395
- PAR ID:
- 10688899
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Chicago
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 997
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 330
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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