Tri Astraatmadja
Thompson Postdoctoral Fellow

Tri Astraatmadja

Research Interests

Ground-based astrometric detection of exoplanets; Instrument modeling and simulations; software engineering, scientific computing, and high-performance computing; probability theory, statistical inference, hypothesis testing and data analysis; machine-learning algorithms; large-scale surveys; detection of high-energy neutrinos and photons; kinematical and dynamical studies of the Milky Way

Academics

B.Sc., Astronomy, Institut Teknologi Bandung (2006)
M.Sc., Astronomy, Universiteit Leiden (2008)
Ph.D., Astroparticle Physics, Universiteit Leiden (2012)

Contact & Links

  • (202) 478-4885 | fax: (202) 478-8821
  • tastraatmadja at carnegiescience.edu
  • Department of Terrestrial Magnetism
    Carnegie Institution of Washington
    5241 Broad Branch Road, NW
    Washington, DC 20015-1305
  • Curriculum Vitae
  • Publications
  • Personal Website

Overview

Tri Astraatmadja
Accurate modeling of what Gaia will observe is essential for an accurate estimate of the astrophysical parameters of Gaia sources. Gaia will take low-resolution spectra (called BP/RP spectra) of all detected object, and from these spectra we can identify features that can be used to estimate the astrophysical parameters. To this aim, Tri wrote and developed Ulysses, a simulator that can generate BP/RP spectra from input spectra submitted by the user. In these plots are shown various noise-free BP/RP spectra (bottom plot) as simulated by Ulysses, here for stars with various effective temperatures Teff as indicated by the color code. All other astrophysical parameters are kept the same for all stars: metallicity [Fe/H] = 0, interstellar extinction A0 = 0, and surface gravity log g = 0. The apparent brightness are also all kept the same at G = 15. The top plot shows the corresponding original spectra before they are observed by Gaia. The input spectra are all taken from the PHOENIX library. We can see that the spectra change with the effective temperatures, and the features are preserved in the resulting BP/RP spectra. From these features and by using machine-learning algorithms, we can then extract the effective temperature as well as other parameters.

Tri Astraatmadja comes to DTM as the first Thompson Postdoctoral Fellow. His work at DTM is to improve the data analysis pipeline of the Carnegie Astrometric Planet Search (CAPS) project. The instrument, CAPSCam, has been taking data since 2007, is designed to accurately measure the position of target stars relative to background stars. By repeatedly monitoring the position of target stars from time to time, small changes in their position can be detected and these changes can provide hints on the existence of exoplanets orbiting the target stars. These changes in the position are due to the parallax angle (changes in a star's position due to the Earth's movement around the Sun), the motion of the stars itself, and finally due to the gravitational pull of an exoplanet orbiting the star. In order to discern and decompose all these movements, the position of the target stars have to be measured with extreme accuracy. To achieve this we need to understand how starlight is detected by the instrument, and how it is distorted by the Earth's atmosphere. This understanding can be modeled and should be incorporated into the data analysis.

Before coming to DTM, Tri was working as a postdoctoral researcher at the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany. At the MPIA, Tri was a member of the Gaia astrometric satellite collaboration. Within Gaia, Tri was a part of the group responsible in extracting astrophysical parameters of all sources detected by the satellite. For stellar sources the interesting parameters for examples are temperatures, surface gravity, metallicity, and line-of-sight extinction by interstellar matter. In addition to these Gaia-related works, Tri also works with Coryn Bailer-Jones in investigating the estimation of distance using Gaia parallax.

Tri did his Ph.D. research at the National Institute for Subatomic Physics in Amsterdam, Netherlands, as well as the Physics Department of Leiden University. His Ph.D. project was focused on the detection of very high-energy gamma rays using neutrino telescopes, specifically the ANTARES undersea neutrino telescope, in which he was a member of the collaboration. For this dissertation Tri won the 2015 Global Neutrino Network (GNN) dissertation prize.