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Microlensing and the type Ia supernova iPTF16geu

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

Microlensing and the type Ia supernova iPTF16geu Thumbnail


J.M. Diego

G. Bernstein

W. Chen

A. Goobar

J.P. Johansson

P.L. Kelly

E. Mörtsell


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.


Diego, J., Bernstein, G., Chen, W., Goobar, A., Johansson, J., Kelly, P., …Nightingale, J. (2022). Microlensing and the type Ia supernova iPTF16geu. Astronomy & Astrophysics, 662, Article A34.

Journal Article Type Article
Acceptance Date Mar 23, 2022
Online Publication Date Jun 8, 2022
Publication Date 2022-06
Deposit Date Jul 20, 2022
Publicly Available Date Jul 20, 2022
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 662
Article Number A34


Published Journal Article (2.7 Mb)

Copyright Statement
Diego, J. M. et al, A&A, vol.662, A34, 2022, reproduced with permission, © ESO.

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