Paper

Circumstellar interaction signatures in the low luminosity type II SN 2021gmj

Haislip, Joshua, Janzen, Daryl, Wyatt, Samuel, Pearson, Jeniveve, Kouprianov, Vladimir, Andrews, Jennifer E, Pellegrino, Craig, Reichart, Daniel E, Meza-Retamal, Nicolas, Galbany, Lluis, Lundquist, Michael J, Griffin Hosseinzadeh, Terreran, Giacomo, Howell, D Andrew, Dong, Yize, Sand, David J, Smith, Nathan, Newsome, Megan, Jencson, Jacob E, Valenti, Stefano, Jha, Saurabh W, Shrestha, Manisha, Hoang, Emily T, Hiramatsu, Daichi, F Fabián Rosales-Ortega, Estefania Padilla Gonzalez, Bostroem, K Azalee, Brown, Peter J

2024

Overview

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 (DLT40) 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 Fe~II velocity of \\(\\sim 1800 \\ \\mathrm{km} \\ \\mathrm{s}^{-1}\\) at 50 days past explosion. Using the expanding photosphere method, we derive a distance of \\(17.8^{+0.6}_{-0.4}\\)~Mpc. From the tail of the light curve we obtain a radioactive nickel mass of \\(0.014 \\pm 0.001\\) M\\(_{\\odot}\\). The presence of circumstellar material (CSM) is suggested by the early-time light curve, early spectra, and high-velocity H\\(\\alpha\\) 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\\(_{\\odot}\\) in our hydrodynamic-modeling light curve analysis is also consistent with our spectroscopy. We observe a broad feature near 4600 \\AA, 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.

• Publisher: Cornell University Library, arXiv.org
• Subject: Ejecta / Light curve / Luminosity / Photosphere / Pluto / Red giant stars / Spectrum analysis / Supergiant stars