Circumstellar Interaction Signatures in the Low-luminosity Type II SN 2021gmj

August 2024 • 2024ApJ...971..141M

Authors • Meza-Retamal, Nicolás • Dong, Yize • Bostroem, K. Azalee • Valenti, Stefano • Galbany, Lluís • Pearson, Jeniveve • Hosseinzadeh, Griffin • Andrews, Jennifer E. • Sand, David J. • Jencson, Jacob E. • Janzen, Daryl • Lundquist, Michael J. • Hoang, Emily T. • Wyatt, Samuel • Brown, Peter J. • Howell, D. Andrew • Newsome, Megan • Padilla Gonzalez, Estefania • Pellegrino, Craig • Terreran, Giacomo • Kouprianov, Vladimir • Hiramatsu, Daichi • Jha, Saurabh W. • Smith, Nathan • Haislip, Joshua • Reichart, Daniel E. • Shrestha, Manisha • Rosales-Ortega, F. Fabián • Brink, Thomas G. • Filippenko, Alexei V. • Zheng, WeiKang • Yang, Yi

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 17.8‑0.4+0.6 Mpc. From the tail of the light curve we obtain a radioactive nickel mass of M56Ni = 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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2024ApJ...971..141M
• PREPRINT http://arxiv.org/abs/2401.04027
• ELECTR https://doi.org/10.3847%2F1538-4357%2Fad4d55