"The JWST/MIRI View of the Binary System HK Tau"

Abstract:

The binary system HK Tau is composed of a face-on primary and edge-on secondary disc-bearing stars; this offers a unique opportunity to investigate the spectral features in multiple stellar systems, as the complementary inclination of the two sources allows the simultaneous exploration of both the gaseous and icy state chemistry. In this talk, I present the results obtained from the spectral analysis of the JWST/MIRI observations of both HK Tau A and B. The primary star shows a line-rich spectrum, while HK Tau B is stunningly line-poor – except for atomic ions and molecular hydrogen emission; on the other hand, thanks to the high inclination of B, we confidently detect ice absorption bands of water, CO2, and NH4+. Extended H2 emission coming from the secondary traces a wind originating from the upper layer of the disc around HK Tau B, with a magnetohydrodynamic or photoevaporative origin; the intensity and morphology of the ionised atomic lines further reinforces this interpretation. The stark contrast in the spectra, despite the common stellar origin, is likely to be attributed to a physical mechanism beyond the disc inclination - namely, tidal truncation enhancing disc evolution in the secondary star.