Microlensing and the type Ia supernova iPTF16geu

J. M. Diego, G. Bernstein, W. Chen, A. Goobar, J. P. Johansson, P. L. Kelly, E. Mörtsell, J. W. Nightingale

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3 Scopus citations


The observed magnifications and light curves of the quadruply imaged iPTF16geu supernova (SN) offers a unique opportunity to study a lens system with a variety of independent constraints. The four observed positions can be used to constrain the macrolens model. The magnifications and light curves at the four SN positions are more useful to constrain microlensing models. We define the macrolens model as a combination of a baryonic component that traces the observed light distribution, and a dark matter halo component. We constrained the macrolens model using the positional constraints given by the four observed images, and compared it with the best model obtained when magnification constraints were included. We found that the magnification cannot be explained by a macrolens model alone, and that contributions from substructures such as microlenses are needed to explain the observed magnifications. We considered microlens models based on the inferred stellar mass from the baryonic component of the macrolens model, and used the observed magnification and light curves to constrain the contribution from microlenses. We computed the likelihood of a variety of macro and micro lens models where we varied the dark matter halo, baryonic component, and microlens configurations. We used information about the position, magnification, and, for the first time, the light curves of the four observed SN images. We combined macrolens and microlens models in order to reproduce the observations; the four SN positions, magnifications, and lack of fluctuations in the light curves. After marginalizing over the model parameters, we found that larger stellar surface mass densities are preferred. This result suggests that the mass of the baryonic component is dominated by its stellar component. We conclude that microlensing from the baryonic component suffices to explain the observed flux ratios and light curves.

Original languageEnglish (US)
Article numberA34
JournalAstronomy and Astrophysics
StatePublished - Jun 1 2022

Bibliographical note

Funding Information:
Agencia Estatal de Investigación, Unidad de Excelencia María de Maeztu, ref. MDM-2017-0765. A.G. acknowledges support from the Swedish National Space Agency grant 110/18 and the Swedish Research Council grant 2020-03444. E.M. acknowledges support from the Swedish Research Council under Dnr VR 2020-03384. P.K. is supported by NSF grant AST-1908823, and HST GO-15936, GO-16278, and AR-15791. J.W.N. is supported by the UK Space Agency, through grant ST/N001494/1 and by Innovate UK through grant TS/V002856/1. J.M.D. acknowledges the hospitality of the Physics Department at the University of Pennsylvania for hosting him during the preparation of this work, despite the fact that most of this work was done under strict social distancing rules.

Funding Information:
Acknowledgements. The authors thank Liliya Williams and the anonymous referee for very useful comments and feedback. J.M.D. acknowledges the support of project PGC2018-101814-B-100 (MCIU/AEI/MINECO/FEDER, UE) Minis-terio de Ciencia, Investigación y Universidades. This project was funded by the

Publisher Copyright:


  • Dark matter
  • Gravitational lensing: micro
  • Gravitational lensing: strong
  • Supernovae: individual: iPTF16geu


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