iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova

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Science  21 Apr 2017:
Vol. 356, Issue 6335, pp. 291-295
DOI: 10.1126/science.aal2729
  • Fig. 1 Spectroscopic identification of iPTF16geu as a type Ia supernova and measurements of the redshifts of the SN host galaxy and the intervening lensing galaxy.

    Measurements of the SN spectral energy distribution Fλ obtained with the P60, P200, and NOT telescopes are best fitted by a normal SN Ia spectral template. (A) Comparison with a nearby SN Ia, SN 2011fe, redshifted to z = 0.409 (green line) (22) at a similar rest-frame phase, expressed in units of days with respect to the time of the optical light curve maximum. The spectra also reveal narrow absorption and emission lines, marked by the dashed vertical lines, from which the redshifts of the lens (z = 0.216, blue lines) and SN host galaxy (z = 0.409, red lines) were determined. (B to D) Zoomed-in view in rest-frame wavelengths of the Ca ii H&K absorption features (B), the Na i D absorption features (C), and the Hα and [N ii] emission lines (D). The Hα and [N ii] emission lines at z = 0.216 were used to fit the velocity dispersion of matter in the lensing galaxy, σv = Embedded Image km s–1.

  • Fig. 2 Multicolor light curve of iPTF16geu showing that the supernova is 4.3 magnitudes (30 standard deviations) brighter than expected.

    The magnitudes are measured with respect to time of maximum light (modified Julian date 57653.10) in the R-band at P48 and in the g-, r-, and i-bands with the SED Machine RC at P60. The filter transmission functions are shown in (24). The solid lines show the best-fitted SALT2 (17) model to the data. The dashed lines indicate the expected light curves at z = 0.409 (without lensing); the bands represent the standard deviation of the brightness distribution for SNe Ia. To fit the observed light curves, a brightness boost of 4.3 magnitudes is required.

  • Fig. 3 Image of the field of iPTF16geu showing the spatial resolution of the ground-based instruments used in this work.

    Left: Pre-explosion multicolor image from SDSS indicating the bright natural guide star. (A) Position of the SN detection in the R-band at P48 (zoomed-in view near the galaxy SDSS J210415.89-062024.7). (B and C) Improved spatial resolution with the use of NGSAO (B) and LGSAO (C).

  • Fig. 4 High-spatial-resolution images from the Hubble Space Telescope and the Keck Observatory used to resolve the positions of the SN images, the partial Einstein ring of the host galaxy, and the intervening lensing galaxy.

    (A to C) HST/WFC3 observations of iPTF16geu obtained on 25 October 2016 in the F475W, F625W, and F814W bands, respectively. The images reveal four point sources, except for F475W where SN images 3 and 4 are too faint. (D to F) NIR images obtained using adaptive optics–aided Keck observations in the J-, H-, and Ks-bands, respectively. All four SN images are clearly seen in the J-band (D). For the H- and Ks-band images, both the lensing galaxy at the center of the system and the lensed partial Einstein ring of the host galaxy are visible.

Supplementary Materials

  • iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova

    A. Goobar, R. Amanullah, S. R. Kulkarni, P. E. Nugent, J. Johansson, C. Steidel, D. Law, E. Mörtsell, R. Quimby, N. Blagorodnova, A. Brandeker, Y. Cao, A. Cooray, R. Ferretti, C. Fremling, L. Hangard, M. Kasliwal, T. Kupfer, R. Lunnan, F. Masci, A. A. Miller, H. Nayyeri, J. D. Neill, E. O. Ofek, S. Papadogiannakis, T. Petrushevska, V. Ravi, J. Sollerman, M. Sullivan, F. Taddia, R. Walters, D. Wilson, L. Yan, O. Yaron

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

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