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arXiv · 2603.12991

Detection of a molecular hydrogen envelope around nova GK Persei

D. P. K. Banerjee·A. Evans·T. Liimets·C. E. Woodward·T. R. Geballe·V. Joshi·S. Starrfield
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Abstract

The eruption of Nova Persei 1901 (GK Per) occurred 125 yrs ago; remarkably it still holds major surprises. Using data from the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), we find it has a bipolar molecular hydrogen shell. This shell, which has dimensions 18'x10', is co-spatial with the Halpha nebulosity surrounding the nova, which is purported to be an ancient planetary nebula (PN). The shell is detected most strongly in the 0--0 S(9) 4.6947 micron line. A filament of emission in the S(9) 4.6947 micron line is seen 45" SW of GKPer. This coincides, over much of its length, with the site of X-ray and non-thermal radio emission where the 1901 nova ejecta impinges on the ambient medium. We propose that the H_2 emission from the filament arises from the predicted neutral zone between the forward and reverse shocks. Since it is common for bipolar PNe to be accompanied by H_2 envelopes, it ostensibly suggests that the 18'x10' nebulosity is a conventional PN with a luminous, ionizing central source. We show this is not the case, and that the H$\alpha$ nebulosity may be surrounding gas belonging to pre-existing material that was ionized during the 1901 eruption. The ionized gas is presently undergoing recombination on a timescale of ~3000 years, explaining why the nebulosity is still visible.

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D. P. K. Banerjee, A. Evans, T. Liimets, C. E. Woodward, T. R. Geballe, V. Joshi, S. Starrfield. 2026-03-13. Detection of a molecular hydrogen envelope around nova GK Persei. https://arxiv.org/abs/2603.12991

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