An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova

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Science  18 Aug 2017:
Vol. 357, Issue 6352, pp. 680-683
DOI: 10.1126/science.aam8378
  • Fig. 1 Normalized optical spectrum of LP 40-365 as a function of wavelength.

    The spectrum was obtained with the Richey-Chretien Spectrograph at the 4-m telescope (KPNO). Dominant spectral lines of sodium (Na I) and magnesium (Mg I and Mg II) are labeled, along with weaker lines of oxygen (O I), aluminum (Al I) and silicon (Si II). A broad feature near 5230 Å is tentatively identified with a resonance in the Mg I 3p2 photoionization cross section.

  • Fig. 2 Elemental abundances for LP 40-365.

    Photospheric abundances, expressed as the number fraction versus the atomic number, were measured in the high-dispersion spectrum obtained with GRACES at the Gemini-North telescope on Mauna Kea. The atmosphere is dominated by oxygen and neon, followed by sodium and magnesium. Iron is more abundant than nickel and other elements in the iron group by at least a factor of 10. Upper limits are shown with arrows.

  • Fig. 3 Calculated Galactic motion of LP 40-365.

    The orbits are drawn (A) in the Galactic plane (z versus x) and (B) perpendicular to the plane (y versus x) with the GC (solid circle) at the origin. The Sun (Embedded Image) is located 8.5 kpc along the x axis. The current (t = 0) position of LP 40-365 is estimated assuming a distance to the Sun of, from uppermost to lowermost curve, 1000, 800, 600, 400, 300, 200, and 100 pc. The past trajectory resulting from an assumed distance of 300 pc is marked with open circles at, from rightmost to leftmost curve, –3, –10, and –30 million years. Schematic views of the Galactic arms are shown in gray.

  • Table 1 Stellar data and parameters.

    The celestial coordinates are provided along the right ascension (RA ≡ α) and declination (Dec ≡ δ) and the apparent motion of the star, i.e., the proper motion μ, is decomposed into μα cos δ along the right ascension and μδ along the declination.

    RA (J2000)14h06m35s.45
    Dec (J2000)+74°18′58″.0
    μα cos δ–56 ± 7 mas year–1
    μδ148 ± 7 mas year–1
    mV15.51 ± 0.09 mag
    TeffEmbedded Image
    log g/(cm s–2)Embedded Image
    MassEmbedded Image
    RadiusEmbedded Image
    MVEmbedded Image
    v sin i30.5 ± 2.0 km s–1

Supplementary Materials

  • An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova

    S. Vennes,s P. Nemeth, A. Kawka, J. R. Thorstensen, V. Khalack, L. Ferrario, E. H. Alper

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S8
    • Tables S1 and S2
    • References

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