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Machine-Based Spectral Classification of Weak CN and Carbon Stars in M31

POSTER

Abstract

Stellar evolution has been researched for decades, yet certain phases of the stellar life cycle remain poorly understood. Recent analyses of spectroscopic and photometric data of stars in the Andromeda Galaxy (M31) from the Spectroscopic Landscape of Andromeda's Stellar Halo (SPLASH) and the Panchromatic Hubble Andromeda Treasury (PHAT) surveys have revealed an unusual population of "weak CN" stars that represent such a phase. Their defining feature is a weak double-peaked spectral absorption line around 8000 angstroms indicating the presence of the CN molecule; this same feature appears more strongly in carbon stars. Using data from SPLASH and PHAT, we investigated this association by developing an algorithm that spectrally classified stars as ``carbon'', ``weak CN'', or ``other''. The algorithm performs a clustering analysis comparing spectral features present in the visually classified stars. The results were plotted in color-magnitude diagrams (CMDs) to compare the training set with the algorithm; the algorithm classified more accurately. The results obtained have been instrumental in establishing weak CN stars as a well-defined stage of stellar evolution and will contribute to a greater understanding of the physical properties of carbon and weak CN stars.

Authors

  • Suhas Kotha

    Evergreen Valley High School

  • Rachel Raikar

    University of California Santa Cruz

  • Puragra Guhathakurta

    University of California Santa Cruz, University of California Santa Cruz, Santa Cruz, CA, United States, UC Santa Cruz

  • Antara Bhattacharya

    SLAC National Accelerator Laboratory, Department of Physics, University of Nevada, Reno, 89557, USA, School of Mathematics and Physics, the University of Queensland, Brisbane, QLD 4072, Australia, University of California, Berkeley, National Institute for Materials Science, Lawrence Berkeley National Lab, Chemical Engineering, Stanford University, Santa Clara University, Lawrence Livermore National Laboratory, University of California San Diego, University of Nevada, Reno, Nihon University, Osaka U., LLNL, SLAC, U. of Nevada, Reno, California State University, Chico, Lawrence Livermore National Laboratory; UC, Irvine, Chemical Engineering and Materials Science, University of Minnesota Twin Cities, Physics, California Polytechnic State University, San Luis Obispo, Oak Ridge National Lab, Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407, USA, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6021, New Zealand, California Polytechnic State University, University of California, Santa Barbara, Department of Physics, California Polytechnic State University, Victoria University of Wellington, Palo Alto High School, Palo Alto, CA, Navy Children School, Mumbai, Maharashtra, India

  • Antara Bhattacharya

    SLAC National Accelerator Laboratory, Department of Physics, University of Nevada, Reno, 89557, USA, School of Mathematics and Physics, the University of Queensland, Brisbane, QLD 4072, Australia, University of California, Berkeley, National Institute for Materials Science, Lawrence Berkeley National Lab, Chemical Engineering, Stanford University, Santa Clara University, Lawrence Livermore National Laboratory, University of California San Diego, University of Nevada, Reno, Nihon University, Osaka U., LLNL, SLAC, U. of Nevada, Reno, California State University, Chico, Lawrence Livermore National Laboratory; UC, Irvine, Chemical Engineering and Materials Science, University of Minnesota Twin Cities, Physics, California Polytechnic State University, San Luis Obispo, Oak Ridge National Lab, Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407, USA, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6021, New Zealand, California Polytechnic State University, University of California, Santa Barbara, Department of Physics, California Polytechnic State University, Victoria University of Wellington, Palo Alto High School, Palo Alto, CA, Navy Children School, Mumbai, Maharashtra, India