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Spectroscopy of the first resolved strongly lensed Type Ia supernova iPTF16geu

Johansson, J. and Goobar, A. and Price, S. H. and Sagués Carracedo, A. and Della Bruna, L. and Nugent, P. E. and Dhawan, S. and Mörtsell, E. and Papadogiannakis, S. and Amanullah, R. and Goldstein, D. and Cenko, S. B. and De, K. and Dugas, A. and Kasliwal, M. M. and Kulkarni, S. R. and Lunnan, R. (2020) Spectroscopy of the first resolved strongly lensed Type Ia supernova iPTF16geu. . (Unpublished)

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We report the results from spectroscopic observations of the multiple images of the strongly lensed Type Ia supernova (SN Ia), iPTF16geu, obtained with ground based telescopes and the Hubble Space Telescope (HST). From a single epoch of slitless spectroscopy with HST, we can resolve spectra of individual lensed supernova images for the first time. This allows us to perform an independent measurement of the time-delay between the two brightest images, Δt=1.4±5.0 days, which is consistent with the time-delay measured from the light-curves. We also present measurements of narrow emission and absorption lines characterizing the interstellar medium in the host galaxy at z = 0.4087, as well as in the foreground lensing galaxy at z = 0.2163. We detect strong Na ID absorption in the host galaxy, indicating that iPTF16geu belongs to a subclass of SNe Ia displaying "anomalously" large Na ID column densities in comparison to the amount of dust extinction derived from their light curves. For the deflecting galaxy, we refine the measurement of the velocity dispersion, σ = 129 ± 4 km s⁻¹, which significantly constrains the lens model. Since the time-delay between the SN images is negligible, we can use unresolved ground based spectroscopy, boosted by a factor ~70 from lensing magnification, to study the properties of a high-z SN Ia with unprecedented signal-to-noise ratio. The spectral properties of the supernova, such as pseudo-Equivalent widths of several absorption features and velocities of the Si II-line indicate that iPTF16geu, besides being lensed, is a normal SN Ia, indistinguishable from well-studied ones in the local universe, providing support for the use of SNe Ia in precision cosmology. We do not detect any significant deviations of the SN spectral energy distribution from microlensing of the SN photosphere by stars and compact objects in the lensing galaxy.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Johansson, J.0000-0001-5975-290X
Goobar, A.0000-0002-4163-4996
Nugent, P. E.0000-0002-3389-0586
Papadogiannakis, S.0000-0003-0783-3323
Amanullah, R.0000-0002-5559-9351
Goldstein, D.0000-0003-3461-8661
Cenko, S. B.0000-0003-1673-970X
De, K.0000-0002-8989-0542
Kasliwal, M. M.0000-0002-5619-4938
Kulkarni, S. R.0000-0001-5390-8563
Lunnan, R.0000-0001-9454-4639
Additional Information:We thank E. Zackrisson and A. Adamo for helpful discussions. We thank T. Brink, R. Bruch, Cooper, S. Goldwasser, A. Ho, I. Irani, B. Jain, Y. Sharma, A. Tzanidakis, Q. Ye andW. Zheng for performing observations. A. G. acknowledges support from the Swedish National Space Agency and the Swedish Research Council. R. L. is supported by a Marie Skłodowska-Curie Individual Fellowship within the Horizon 2020 European Union (EU) Framework Programme for Research and Innovation (H2020-MSCA-IF-2017-794467). A. S. C. acknowledges support from the G.R.E.A.T research environment, funded by Vetenskapsrådet, the Swedish Research Council. The Intermediate Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee (USA), the Oskar Klein Center at Stockholm University (Sweden), the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. These results made use of the Lowell Discovery Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale and by a grant from the Mt. Cuba Astronomical Foundation.
Group:Astronomy Department, Palomar Transient Factory
Funding AgencyGrant Number
Swedish National Space AgencyUNSPECIFIED
Marie Curie FellowshipH2020-MSCA-IF-2017-794467
Swedish Research CouncilUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
John and Ginger GiovaleUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Subject Keywords:gravitational lensing: strong, supernovae: general, supernova: individual (iPTF16geu)
Record Number:CaltechAUTHORS:20200604-151427243
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103707
Deposited By: George Porter
Deposited On:05 Jun 2020 17:37
Last Modified:05 Jun 2020 17:37

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