Kareem El-Badry
California Institute of Technology, CA·Astronomy & Astrophysics·Early-career
About half of all stars live in pairs or larger groups. When two stars orbit closely, they can trade mass, strip each other's outer layers or merge.
- Fields
Astronomy & Astrophysics
Physics
- Topics
binary stars
stellar evolution
Gaia
- Grants
- 2 known grants, through May 2031
What they work on
- Measure how common post-interaction binary stars are across the Milky Way and estimate the mass distribution of black holes and neutron stars, using gaiamock software to correct for which binaries Gaia can detect.
- Test whether stripping of a star's outer layers by a companion produces RR Lyrae pulsating stars, and whether long secondary periods in evolved giants arise from binarity, by modeling Gaia binary data.
- Build an astrometric binary catalog more complete than Gaia's official release, enabling searches for giant planet and brown dwarf companions to nearby stars and studies of massive stars in multiple systems.
- Search Gaia data systematically for hypervelocity white dwarfs that survived Type Ia supernovae, classify about 75 candidates spectroscopically, and model survivors' surface chemistry with TMAP and their evolution with MESA.
- Simulate how supernova debris strikes the companion white dwarf with FLASH hydrodynamics, and use population synthesis to estimate what fraction of Type Ia supernovae come from merging double white dwarfs.
More about the research
These interactions can produce black holes, neutron stars and dead stars called white dwarfs, and can even trigger supernova explosions. Gaia, a space telescope that has built the most precise three-dimensional map of our Galaxy, now lets astronomers find and study such pairs on a large scale. Two projects use Gaia to study how binary stars evolve: one maps binaries across the Milky Way, and the other hunts for stars flung out by exploding white dwarfs.
Why it matters
Type Ia supernovae serve as cosmic yardsticks for measuring the accelerating expansion of the universe, so pinning down how they explode matters for cosmology. Mapping binary stars and their black holes and neutron stars helps explain the sources of gravitational waves. The public catalog and software could also support other searches, such as for giant planets and brown dwarfs orbiting nearby stars.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
Robert Mathieu
University of Wisconsin-Madison, WI·Astronomy & Astrophysics
Build the APOGEE-GALEX-Gaia Catalog, a sample of thousands of white dwarf binaries that have exchanged mass, by combining infrared APOGEE spectra with GALEX ultraviolet data and Gaia data.
Benjamin Williams
University of Washington, WA·Astronomy & Astrophysics
Measure delay time distributions, the time between star formation and the appearance of each object type, for Wolf-Rayet stars, stripped stars and supergiants in resolved Local Group galaxies.
Christopher Kochanek
Ohio State University, OH·Astronomy & Astrophysics
Measure what fraction of massive-star core collapses fail and form a black hole without a supernova, by monitoring evolved stars in 27 nearby galaxies with the Large Binocular Telescope.
The school
California Institute of Technology: 18 labs on PI Pages, $445M a year on research, 200 research doctorates a year.
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