I am a post-doc researcher working with Pier-Emmanuel Tremblay in the Astronomy and Astrophysics group at the University of Warwick. I work on 3D modelling the helium-dominated atmospheres of white dwarfs.

Research

97% of all stars in our Galaxy will end their lives by blowing off their outer layers and leaving a core remnant, known as a white dwarf, behind. As such, white dwarfs are single-handedly the most important stellar remnants for studies of stellar evolution and given that majority of planet hosting stars will end their lives as white dwarfs, they are crucial for understanding what happens to planetary systems as their host stars die. To better understand white dwarfs and therefore aid the various studies involving white dwarfs, we need to be able to determine their fundamental properties, such as their ages, masses and radii. We can do this by looking at observations of white dwarfs. In order to make sense of what the observations show us we need models that realistically describe what happens in the atmospheres of these stars. This is where my work comes in.

I model the helium-dominated atmospheres of white dwarfs (classified as DB and DBA), which make-up around 20% of all known white dwarfs. Up to now, 1D atmospheric models have been used for DB and DBA studies. However in 1D, the treatment of convection, which occurs in the atmospheres of the majority of white dwarfs, is unphysical. Therefore, an improvement must be made in order to extract more accurate parameters. 3D models are thought to be more accurate as they treat convection from first principles using radiation-hydrodynamics. My work is to analyse the first 3D grid of DB and DBA white dwarf atmosphere models and quantify the differences between these new models and the standard 1D models.

These animations show radiative flux leaving the top of the simulations for two 3D DB models. On the left, a DB model with surface gravity of 10^7.5 cm s^-² and effective temperature of around 10,000 K is shown. The DB model on the right, has surface gravity of 10⁹ cm s^-2 and effective temperature of around 34,000 K. Unlike the model with lower surface gravity and effective temperature, this model has well defined intergranular lanes. These models define the two extremes of the 3D DB grid I analyse.

Comic strip I made about my research

Please do not use without permission.

Publications

As a first author:

• 3D spectroscopic analysis of helium-line white dwarfs -- E. Cukanovaite et al., MNRAS (2020)
• Calibration of the mixing length theory for structures of helium-dominated atmosphere white dwarfs -- E. Cukanovaite et al., MNRAS, 490, 1010 (2019)
• Pure-helium 3D model atmospheres of white dwarfs -- E. Cukanovaite et al., MNRAS, 481, 1522 (2018)

As a co-author:

• Fundamental parameter accuracy of DA and DB white dwarfs in Gaia Data Release -- P.-E. Tremblay et al., MNRAS, 482, 5222 (2019)
• Core crystallization and pile-up in the cooling sequence of evolving white dwarfs -- P.-E. Tremblay et al., Nature, 565, 202 (2019)

• A Gaia Data Release 2 catalogue of white dwarfs and a comparison with SDSS -- N. P. Gentile Fusillo et al., MNRAS, 482, 4570 (2019)
• Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface -- M. J. Green et al., MNRAS, 485, 1947 (2019)

• Overview of the DESI Legacy Imaging Surveys -- A. Dey et al., AJ, 157, 168 (2019)

Talks and posters

Talks:

• 3D models of DB and DBA white dwarfs - IAUS 357 held in Hilo, Hawaii on the 25th of October, 2019. Won best talk in session.
• 3D models of helium-atmosphere white dwarfs -- Warwick-Birmingham Science Meet-Up held at University of Warwick, Coventry, UK on the 17th December, 2018
• First 3D simulations of white dwarfs with pure-helium atmospheres -- 21st European Workshop on White Dwarfs held in Austin, Texas, USA from 23rd to 27th July of 2018. Watch the talk here.

Outreach Talks:

• Modelling white dwarf atmospheres - Presented to the AstroSoc society at the University of Warwick on the 19th November, 2019.

Posters:

• First 3D simulations of pure-helium atmosphere white dwarfs -- Winter School for Astrophysics held in La Laguna, Tenerife, Spain from 13th to 17th November 2017. My poster won the Favourite Poster (Lecturer's vote) award.
• First 3D simulations of pure-helium atmosphere white dwarfs and The new generation of white dwarf models and gaps in our knowledge of helium spectral lines -- 2 posters presented at EWASS 2018 held in Liverpool, UK from 3rd to 6th of April, 2018.
• First 3D simulations of pure-helium atmosphere white dwarfs -- Current Challenges in the Physics of White Dwarf Stars conference held in Santa Fe, New Mexico, USA from 12th to 16th of June, 2017.

Other

• Nature Behind the Paper - First direct evidence of core crystallisation in white dwarfs -- a blog-type article I wrote about the Core crystallization and pile-up in the cooling sequence of evolving white dwarfs paper I worked on.