Adaptive Optics and planned HST follow-up observations of the strongly lensed SNIa iPTF16geu

ATel #9626; Ariel Goobar, Rahman Amanullah (Stockholm University and the Oskar Klein Centre), Shri Kulkarni (Caltech) on behalf of the intermediate Palomar Transient Factory collaboration; and Charles Steidel (Caltech), David Law (STScI)
on 14 Oct 2016; 18:39 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ariel Goobar (ariel@fysik.su.se)

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Adaptive optics (AO) observations of iPTF16geu (ATel #9603) were carried out on October 11 with NACO in Natural Guide Star (NGS) mode on VLT. A bright star 30" SE of the SN position provided for the AO corrections. The resulting Ks band image had a PSF with approximately 0.3" FWHM. On October 13, the SN was observed in H-band, this time at the Keck 1 telescope, with the Laser Guide System (LGS) AO and the OSIRIS imager. The PSF was measured to be 0.07" FWHM. The Keck AO images show a partial Einstein ring, 0.27 arcseconds from the lens, containing images of both the supernova and the SN host galaxy. This confirms the strong lensing nature of the system. We further identify the probable locations of two SN images, as marked in the finding chart based on the Keck image (follow the link at the bottom).

11 orbits of HST observations have been approved (DDT) to further study this unique SN, which may allow us to find more multiple SN images in this system and, potentially, measure time delays between them, as well as the extinction in the lines of sight. The HST observations, with 3 days cadence, are scheduled to start on Oct 24, or possibly a few days earlier, if feasible.

The NACO images provide precious information to study iPTF16geu, a rare case where we have restframe near-IR observations at z=0.4. A second epoch is planned with the same set-up.

The iPTF collaboration is obtaining nightly optical observations, mostly in R and i-band (currently R~20), as well as regular spectroscopy at optical wavelengths. We encourage observers to carry out complementary observations, especially in the near-IR, so that the science return of this unique transient can be maximized.

We kindly ask interested observers to keep us informed of (planned) observations (e-mail ariel@fysik.su.se and rahman@fysik.su.se).

Link to site with AO image of iPTF16geu and finding chart (SN cosmology group at the Oskar Klein Centre)