Ylva Götberg

Astronomer

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ygoetberg@carnegiescience.edu

Carnegie Observatories
813 Santa Barbara St
Pasadena, CA-91101, USA

About me

My name is Ylva Götberg and I am a postdoctoral fellow at the Carnegie Observatories located in Pasadena, California.

I am interested in binary stellar evolution and the effect of binary interactions on surrounding environments, both nearby and at high redshift.

Mainly, I use the codes MESA and CMFGEN to model the evolution and spectra of binary stars. So far, my focus has been on stars that lose their hydrogen-rich envelopes through mass transfer with a companion star.

I recently obtained my PhD degree at the University of Amsterdam, working together with Selma de Mink. You can find my thesis here.

News

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PhD Graduation

With my PhD thesis entitled "The properties and impact of stars stripped in binaries", I graduated the 7 of February 2019 at the University of Amsterdam, Anton Pannekoek Institute for Astronomy.

The photo shows when I receive the diploma from the committee member prof. Alex de Koter. Next to him, my supervisor Dr. Selma de Mink and promotor prof. Michiel van der Klis.

My thesis online

Research projects

Highlights of my recent and ongoing research


Stripped stars: subdwarfs to WR stars

(Götberg, de Mink, Groh, Kupfer, Crowther, Zapartas & Renzo, 2018, A&A, 615, A78)

We create the first grids of spectral models for stripped stars over a large range of mass. These show a smooth sequence bridging subdwarfs with Wolf-Rayet stars.

Candidate stripped stars in the LMC?

(Smith, Götberg & de Mink, 2018, MNRAS, 475, 772)

The WN3/O3 stars in the LMC show indications of being stars stripped in binaries.

Stripped stars with different metallicities

(Götberg, de Mink, & Groh, 2017, A&A, 608, A11)

We present the first spectral models made particularly for intermediate mass stars that are stripped in binaries, covering a range of metallicities.

Additional projects:


Models

Models in Götberg et al. 2018:
These models are for a range of mass of stars stripped in binaries. We provide models for four metallicities (Z = 0.014, 0.006, 0.002, 0.0002).

Evolutionary models    Spectral models

Models in Götberg et al. 2017:
These models are for stars stripped in binaries for a range of metallicities (Z = 0.0001-0.05). The systems are initially composed of a 12 M and a 5 M star on a 20 day orbit around each other.

  • Evolutionary models (MESA inlists, history files in folder below)
  • Spectral models (see folder below)
Evolutionary models    Spectral models

Models in Smith et al. 2018:
These models are for stars stripped in binaries with the metallicity Z = 0.004 and that are expected to show both absorption and emission features.

  • Evolutionary models (MESA inlists, history files in folder below)
  • Spectral models (see folder below)
Evolutionary models    Spectral models

Outreach

Recorded outreach presentations:

Astronomy on Tap, Santa Barbara, 2017

Astronomy on Tap, Leiden, 2017



My amateur artist's impressions:


Cartoon visualizing stable mass transfer in a binary system. Download here.
The most massive star in the system evolves faster and starts to swell up when hydrogen is depleted in the center and ignited in a shell around the core (the star enters the Hertzsprung gap phase). At some point during this phase, the star is large enough for the outer layers of the star to feel a stronger gravitational force towards the companion star than to itself. This is when mass transfer starts and gaseous material starts flowing to the companion star. The companion starts accreting the transferred material, but is also spun up by the process. When most of the envelope of the donor star is lost, the hot and compact helium-rich core of the star is visible. This stripped star is blue and happy in the video.
(This video was created by Ylva Götberg for the program "BinCosmos", PI: de Mink.)




Homemade, not fully realistic artist's impressions of binary stars. (Created by Ylva Götberg)

Ylva Götberg

Email: ygoetberg@carnegiescience.edu
Tel: +1 (626) 304-0236

Carnegie Observatories
813 Santa Barbara Street
91101 Pasadena, California
U.S.A.