Intermediate Luminosity Type Iax SN 2019muj With Narrow Absorption Lines: Long-Lasting Radiation Associated With a Possible Bound Remnant Predicted by the Weak Deflagration Model

We present comprehensive spectroscopic and photometric analyses of the intermediate luminosity type lax supernova (SN lax) 2019muj based on multi-band datasets observed through the framework of the OISTER target-of-opportunity program. SN 2019muj exhibits almost identical characteristics to the subluminous SNe lax 2008ha and 2010ae in terms of the observed spectral features and the light curve evolution at the early phase, except for the peak luminosity. The long-term observations unveil late-time flattening light curves as seen in luminous SN lax 2014dt. This can be explained by the existence of an inner dense and optically thick component possibly associated with a bound white dwarf remnant left behind after the explosion. We demonstrate that the weak deflagration model with a wide range of explosion parameters can reproduce the late-phase light curves of other SNe lax. Therefore, we conclude that a common explosion mechanism operates for different subclass SNe lax.
DST-JSPS grant [DST/INT/JSPS/P-281/2018]; Optical and Near-infrared Astronomy Inter-University Cooperation Program; JSPS KAKENHI [JP19K23461, 21K13959, JP20H00174, JP20H04737, JP18H04585, JP18H05223, JP17H02864, JP17K14253]; Turkish Scientific and Technical Research Council (TUBITAK-2211C); Turkish Scientific and Technical Research Council (TUBITAK-2214A); [19B-N-CN02]; [19B-N-CT01]
We are grateful to the staff at the Seimei and Subaru telescopes for their support. The spectral data using the Seimei telescope were taken under the programs 19B-N-CN02, 19B-N-CT01. The latephase observation was performed with the Subaru telescope under S19B-055. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawaii. We thank the support staff at IAO and CREST who enabled the 2m HCT observations. The IAO is operated by the Indian Institute of Astrophysics, Bangalore, India. D.K.S. and G.C.A. acknowledge partial support through DSTJSPS grant DST/INT/JSPS/P-281/2018. The authors also thank T. J. Moriya and M. Tanaka for insightful comments. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with theNational Aeronautics and Space Administration. The spectral data of comparison SNe were downloaded from the SUSPECT7 (Richardson et al. 2001) and WISeREP8 (Yaron & Gal-Yam 2012) databases. This research has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Astrophysics Science Division at NASA/GSFC and of the Smithsonian Astrophysical Observatory's High Energy Astrophysics Division. This work is supported by the Optical and Near-infrared Astronomy Inter-University Cooperation Program. The authors declare that there is no conflict of interests. M.K. acknowledges support by JSPS KAKENHI Grants (JP19K23461, 21K13959). K.M. acknowledges support by JSPS KAKENHI Grants (JP20H00174, JP20H04737, JP18H04585, JP18H05223, JP17H02864). M.Y. is partly supported by JSPS KAKENHI Grant (JP17K14253). U.B. acknowledges the support provided by the Turkish Scientific and Technical Research Council (TUBITAK-2211C and 2214A).