Circumstellar Interaction Signatures in the Low-luminosity Type II SN 2021gmj
Abstract
We present comprehensive optical observations of SN 2021gmj, a Type II supernova (SN II) discovered within a day of explosion by the Distance Less Than 40 Mpc survey. Follow-up observations show that SN 2021gmj is a low-luminosity SN II (LL SN II), with a peak magnitude M V = ‑15.45 and an Fe II velocity of ∼1800 km s‑1 at 50 days past explosion. Using the expanding photosphere method, we derive a distance of Mpc. From the tail of the light curve we obtain a radioactive nickel mass of = 0.014 ± 0.001 M ⊙. The presence of circumstellar material (CSM) is suggested by the early-time light curve, early spectra, and high-velocity Hα in absorption. Analytical shock-cooling models of the light curve cannot reproduce the fast rise, supporting the idea that the early-time emission is partially powered by the interaction of the SN ejecta and CSM. The inferred low CSM mass of 0.025 M ⊙ in our hydrodynamic-modeling light-curve analysis is also consistent with our spectroscopy. We observe a broad feature near 4600 Å, which may be high-ionization lines of C, N, or/and He II. This feature is reproduced by radiation-hydrodynamic simulations of red supergiants with extended atmospheres. Several LL SNe II show similar spectral features, implying that high-density material around the progenitor may be common among them.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2024
- DOI:
- 10.3847/1538-4357/ad4d55
- arXiv:
- arXiv:2401.04027
- Bibcode:
- 2024ApJ...971..141M
- Keywords:
-
- Core-collapse supernovae;
- Type II supernovae;
- Circumstellar matter;
- Stellar mass loss;
- Red supergiant stars;
- 304;
- 1731;
- 241;
- 1613;
- 1375;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted version at ApJ