The study found that SN 2019odp is an oxygen-rich type Ib supernova

An international team of astronomers has made follow-up optical and spectral observations of a supernova called SN 2019odp. Results of the monitoring campaign, published March 24 arXiv Preprint server, indicates that SN 2019odp is a massive, oxygen-rich Type Ib supernova.

Supernovae (SNe) are powerful, luminous stellar explosions. They are important to the scientific community because they provide essential evidence for the evolution of stars and galaxies. In general, SNe are divided into two groups based on their atomic spectra: type I and type II. Type I SNe lacks hydrogen in its spectra, while type II displays hydrogen spectral lines.

Type Ib (SNeIb) supernovae are a subclass of SNe of the naked envelope core collapse. They form when a massive star, along with its outer shell of hydrogen, collapses under its own gravity. SNe Ib may be essential for improving our understanding of the evolution of massive stars, the interaction after the explosion, and the properties of the resulting supernovae. The presence of helium also distinguishes between the helium-rich type Ib SNe and the helium-poor type Ic.

SN 2019odp, also known as ZTF19abqwtfu, was detected on August 21, 2019, as part of the Zwicky Transient Facility (ZTF) survey. The supernova is located about 208 million light-years away, in spiral galaxy UGC 12373. Shortly after its discovery, SN 2019odp was initially classified as a type Ic-BL (outlined) supernova as part of the ePESSTO+ survey.

Now, new observations by a group of astronomers led by Tassilo Schweier of Stockholm University in Sweden indicate that SN 2019odp should be reclassified as a type Ib supernova.

“We present and analyze observations of the type Ib(SN) 2019odp supernova (also known as ZTF19abqwtfu) covering epochs within days from the explosion to the nebular phase at 360 d after the explosion. … Our observations include mainly optical observations in the optical field and Low- to medium-resolution spectral observations covering the entire observable time scale. We expand on existing methods for deriving oxygen mass estimates from nebula phase spectroscopy,” the researchers wrote in the paper.

Observations revealed the presence of helium in the SN 2019odp ejecta, indicating a type Ib nature. Furthermore, the spectra have linewidths much smaller than those typically associated with type Ic-BL supernovae, further supporting the type Ib scenario.

However, the pre-peak spectra of SN 2019odp have a high spectral similarity to Ic-BL-type supernovae as well as other transitional SNe. This, according to astronomers, may indicate a common scenario for all of these early supernovae.

The study also found that SN 2019odp is a high-mass oxygen-rich supernova with an ejecta mass estimated to be between 4-7 solar masses and the oxygen mass calculated to be at least 0.5 solar masses. Therefore, the results point to a progenitor, most likely a Wolf-Rayet star with a pre-explosion mass greater than 18 solar masses.

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