Research Article

Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source

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Science  22 Dec 2017:
Vol. 358, Issue 6370, pp. 1556-1558
DOI: 10.1126/science.aap9811
  • Fig. 1 Gravitational wave localization of GW170817.

    The outer edge of the red region represents the 90% confidence region as extracted from the revised BAYESTAR probability map. Also shown for context is the Milky Way (in blue), with the outermost blue contour corresponding to V-band extinction AV = 0.5 mag (34). The thick solid line represents the horizon as seen from the Swope Telescope on 17 August 2017 at 23:33 UT, the time we observed SSS17a. The dotted line represents an elevation above the horizon of 30° (corresponding to an air mass of 2.0).

  • Fig. 2 Sky region covering the 90% confidence region for the location of GW170817.

    The 50%, 70%, and 90% contours are shown, with contours extracted from the same probability map as Fig. 1. Gray circles represent the locations of galaxies in our galaxy catalog and observed by the Swope Telescope on 17 to 18 August 2017 to search for the EM counterpart to GW170817. The size of the circle indicates the probability of a particular galaxy being the host galaxy for GW170817. The square regions represent individual Swope pointings, with the solid squares specifically chosen to contain multiple galaxies (and labeled in the order in which they were observed) and the dotted squares being pointings that contain individual galaxies. The blue square labeled “9” contains NGC 4993, the location of which is marked by the blue circle, and SSS17a. FOV, field of view.

  • Fig. 3 Full-field Swope Telescope i-band image containing NGC 4993.

    For the location of NGC 4993, see field 9 in Fig. 2. The bright stars Ψ Hydrae and HD 114098 are labeled. The galaxies NGC 4993 and ESO 508-G014, which had probabilities of hosting GW170817 of 0.022 and 0.009, respectively (table S1), are labeled and marked with red arrows.

  • Fig. 4 Images centered on NGC 4993, with north up and east left.

    Image dimensions are 3 arc min by 3 arc min. (A) Hubble Space Telescope F606W-band (broad V) image captured 4 months before the GW trigger (25, 35). (B) Swope image of SSS17a. The i-band image was obtained on 17 August 2017 at 23:33 UT by the Swope Telescope at Las Campanas Observatory. SSS17a is marked with the red arrow. No object is present in the Hubble image at the position of SSS17a (25, 35).

Supplementary Materials

  • Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source

    D. A. Coulter, R. J. Foley, C. D. Kilpatrick, M. R. Drout, A. L. Piro, B. J. Shappee, M. R. Siebert, J. D. Simon, N. Ulloa, D. Kasen, B. F. Madore, A. Murguia-Berthier, Y.-C. Pan, J. X. Prochaska, E. Ramirez-Ruiz, A. Rest, C. Rojas-Bravo

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

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S6
    • Tables S1 and S2
    • References

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