The compact object and innermost ejecta of SN 1987A

Larsson, J., Fransson, C., Kavanagh, P. J., Sargent, B., Barlow, M. J., Matsuura, M. ORCID: https://orcid.org/0000-0002-5529-5593, Gall, C., Gehrz, R. D., Habel, N., Hirschauer, A. S., Jones, O. C., Kirshner, R. P., Meixner, M., Rosu, S. and Temim, T. 2025. The compact object and innermost ejecta of SN 1987A. [Online]. ArXiv: Cornell University. Available at: https://doi.org/10.48550/arXiv.2508.03395 Item availability restricted.

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Abstract

The first JWST observations of SN 1987A provided clear evidence that a compact object is ionizing the innermost ejecta. Here we analyze a second epoch of JWST NIRSpec and MIRI/MRS observations to better characterize the properties of this region, aided by a higher spectral resolving power for the new NIRSpec data. We confirm the presence of the previously identified narrow lines from the central region; [Ar VI] 4.5292 m, [Ar II] 6.9853 m, [S IV] 10.5105 m, and [S III] 18.7130 m, and also identify similar components in [Ca V] 4.1585 m, [Cl II] 14.3678 m, and possibly [Fe II] 1.6440 m. These lines are blueshifted by -250 km/s, while the emission region is spatially unresolved and located southeast of the center. The offset and blueshift could imply a kick velocity of km/s for the neutron star. We also identify [Ca IV] 3.2068 m near the center, but it is displaced to the north and has a redshift of km/s. We find that scattering by dust in the ejecta with a typical grain size m can explain the [Ca IV] properties and the absence of other narrow lines at shorter wavelengths, while dust absorption is important at m. Photoionization models for a pulsar wind nebula and a cooling neutron star are both compatible with the observations, with the exception of the [Fe II] feature. The two models primarily differ at short wavelengths, where new lines are expected to emerge over time as the optical depth of dust in the expanding ejecta decreases.

Item Type:	Website Content
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Physics and Astronomy
Publisher:	Cornell University
Date of First Compliant Deposit:	15 August 2025
Date of Acceptance:	31 July 2025
Last Modified:	19 Aug 2025 11:30
URI:	https://orca.cardiff.ac.uk/id/eprint/180458

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