The Most Recent Observations of Nearby Type Ia Supernovae

[Glitch]

Abstract
We report deep radio observations of nearby Type Ia Supernovae (SNe Ia) with the electronic Multi-Element Radio Linked Interferometer Net-work (e-MERLIN), and the Australia Telescope Compact Array (ATCA). No detections were made. With standard assumptions for the energy densities of relativistic electrons going into a power-law energy distribution, and the magnetic field strength (epsilon_e = epsilon_B = 0.1), we arrive at the upper limits on mass-loss rate for the progenitor system of SN 2013dy (2016coj, 2018gv, 2018pv, 2019np), to be less than 12 (2.8,1.3, 2.1, 1.7)EE(-8) solar masses per year (for a wind speed of 100 km/s). To SNe 2016coj, 2018gv, 2018pv and 2019np we add radio data for 17 other nearby SNe Ia, and model their non-detections. With the same model as described, all 21 SNe Ia have mass-loss rates less than 4EE(-8) solar masses per year (for a wind speed of 100 km/s). We compare those limits with the expected mass loss rates in different single-degenerate progenitor scenarios. We also discuss how information on epsilon_e and epsilon_B can be obtained from late observations of SNe Ia and the youngest SN Ia remnant detected in radio, G1.9+0.3, as well as stripped-envelope core-collapse SNe. We highlight SN 2011dh, and argue for epsilon_e approximately equal to 0.1 and epsilon_B approximately equal to 0.0033. Finally, we discuss strategies to observe at radio frequencies to maximize the chance of detection, given the time since explosion, the distance to the supernova and the telescope sensitivity.

The Deepest Radio Observations of Nearby Type IA Supernovae: Constraining Progenitor Types and Optimizing Future Surveys
--- The Astrophysical Journal, Volume 890, Number 2, February 2020 (free preprint)

First, I want to say that I have absolutely no issues with the data in this latest survey. In fact, I found the paper fascinating because it included new data that had not been observed before. The more data we are able to collect, the better. Particularly in this case with Type Ia supernovae since it is being used as a Standard Candle for measuring cosmological distances, among other things like determining the age of the universe and how quickly the universe is expanding, and our understanding of the Lambda-CDM model. So there is a lot at stake to get it right.

My one and only issue with the survey is that it is not as thorough as it should be. It is in effect, incomplete.

There is another type of supernovae that has an identical light curve to Type Ia supernovae, only they appear significantly dimmer than the Type Ia used as our Standard Candle. In March, 2013, these extremely dim Type Ia supernovae were classified as Type Iax supernovae. It is thought that these dim Type Iax supernovae are a partial deflagration, often leaving behind at least a piece of the progenitor. If not distinguished from the normal Type Ia supernovae their dimmer magnitude would make them appear much further away than they actually are.

Fortunately, there are ways to easily distinguish between the two, but it requires collecting the data. All Type Iax supernovae have ejecta velocities under 8,000 km/s. While all Type Ia supernovae have ejecta velocities greater than 10,000 km/s. Unfortunately this paper does not include ejecta velocities for any of the supernovae in its survey.

Approximately 32.5% (17% > 31% < 48%) of all Type Ia supernovae classified before 2013 were misclassified and should be Type Iax supernovae instead. This is why it is critical to be able to distinguish the difference between the two.

Source:
Type Iax Supernovae: A New Class of Stellar Explosion* - The Astrophysical Journal, Volume 767, Number 1, March 2013

 

[Glitch]

Addendum

There is another issue. The paper, in explaining the differences between single-degenerate (SD) and dual-degenerate (DD) resulting in the Type Ia supernovae, the paper states that thus far there have been no observed white dwarf stars in a close binary orbit. The paper cites a source published in April 2019.

The non-detections of radio and X-ray emission from SNe Ia have added to a growing consensus that SNe Ia mainly stem from DD explosions (e.g., Maoz et al. 2014), but a potential problem is that no obvious candidate system with double WDs has everbeen identified (Rebassa-Mansergas et al. 2019)

Well, the paper they cite was just a few months pre-mature. In July 2019 we discovered the very first binary white dwarf stars in close orbit.

Astronomers Discover Record-Breaking White Dwarf Binary - Sci-News, July 25, 2019