An informal overview of my SN 2014dt research "plain English". For extensive details, please see my article on my Publications page.
My research focuses on one Type Iax supernova in particular, SN 2014dt, which exists in galaxy, M61 at a distance of 12.3-19.3 Mpc (~ 40 – 60 million light years) from Earth. I have used radio and X-ray observations to constrain the environment around the supernova to rule out certain progenitors. SN 2014dt is exciting because it is possibly the closest SN Iax with the deepest limits. The two figures below show that SN 2014dt has the deepest upper limits yet detected in both radio and x-ray wavelengths (i.e. we were able to observe SN 2014dt even though it wasn't very bright and not as powerful as other supernova in its "family").
X-ray observations of SN 2014dt. Note that SN 2014dt has the lowest luminosity of any Iax supernova.
Radio observations of SN 2014dt. Note that SN 2014dt has, next to SN 2012Z, may have the lowest luminosity of any Iax supernova.
Using the upper limits from SN 2014dt shown in the previous two figures, we were able to predict the supernova's light curve (shown below) and use the mass loss/wind velocity to put constraints on SN2014dt's progenitor.
The same data points for SN 2014dt in radio shown above are used here. We then fit "typical Iax light-curves" of the interstellar medium (ISM) from the explosion and the wind from the explosion to those radio observations. Those allowed us to predict values for the mass of the wind and density of the ISM.The different types of lines represent different types of models since it some of the model specifications are unknown (e.g. exact distance, exact time, etc). Using the mass loss values we found above and assuming that the wind was traveling at 100 km/s, we were able to compare the mass loss of other common stars or progenitors and rule out some of the possibilities that were incompatible with our results. All of the progenitors the right of the diagonal red lines in the figure below are progenitor stars that we can rule out. These include RSG stars, LBV winds, some Wolf-Rayet (/Wolf-Rīā/) stars, and some symbiotic stars. However, there are other issues with other progenitors stars that remain unconstrained like Wolf-Rayet stars, MS stars, and nova shells (this goes beyond the scope of this research, but you can read about it in the full publication in my Publication page). Based on our findings, were are left with Helium stars most closely aligning to the possible progenitor of SN 2014dt. This aligns closely with the findings of others as well. Helium stars remain completely unconstrained as progenitors. There has also been some evidence that of Helium star progenitors in previous Iax, such as SN 2012Z.
We are not able to rule out all possible progenitors because the telescope used, the VLA, is not sensitive enough. When the new generation VLA is up and running, we found that if we were to observe another supernova with the luminosity and proximity of SN 2014dt, we may be able to put further constraints on the progenitor of that supernova. However, SN 2014dt is no longer luminous enough to make any further observations that would tell us more about its origins.
A very brief overview of Type Ia and Type Iax supernovae in "plain English"
Supernovae are powerful and luminous stellar explosions that occur at the end of a star's life. As of now, they are classified into two main categories with multiple subcategories: Type I and Type II. At the most basic level, Type I supernovae do not have Hydrogen while Type II do. However, they also thought to have vastly different origins as illustrated in the figure below.
Simplistic Overview of Type I and Type II Supernovae From Pearson, 2005
Currently, my interests lie in the subcategory of Type I supernovae, Type Ia supernovae. These are incredibly useful objects that Astronomers use as "standardizable candles." This means that we can use their intrinsic brightness (i.e. they're actual luminosity and not just the luminosity we observe from Earth) to measure the distance of far-flung galaxies! Despite how much we do know about Type Ia supernovae, there's also a lot that we don't know. Namely, we don't understand what exactly causes these Type Ia supernovae. We know that they likely occur from the collision of two stars (as opposed to a core-collapse), but what types of stars? The two leading scenarios that create a Type Ia supernova (a.k.a the progenitor system) are a double degenerate system (two white dwarf stars colliding) or a single degenerate system (a white dwarf and a larger star colliding).
One way to learn about Type Ia supernovae and their progenitors is to study the anomalies in their class– supernovae that possess many Type Ia qualities, but also have additional caveats. A new and peculiar class of supernovae under the Type Ia category was discovered in 2002 known as Type Iax. Observationally, Type Iax supernovae have some similarities to Type Ia supernovae. However, these Type Iax supernovae are far less luminous and have much lower ejecta velocities (velocity at which material is ejected from the supernova). Discovering why supernovae have the properties they do lie in understanding what the stellar system looked like before it went supernova. Studying the environment around the environment of the explosion allows us work backwards and infer what possible progenitors could have existed.