First study of large-scale magnetic fields and magnetospheric accretion processes in Class I protostars, observed with SPIRou

Magnetic fields are expected to play a key role during the earliest stages of stellar evolution, governing star–disk interactions, angular momentum regulation, and accretion processes. However, the magnetic properties of embedded protostars and the mechanisms driving magnetospheric accretion at these stages remain poorly constrained.

The near-infrared spectropolarimeter SPIRou, installed at the Canada–France–Hawaii Telescope (CFHT), enables the simultaneous investigation of magnetic fields and accretion diagnostics in young stellar objects. As part of the PROMETHEE (Protostellar Magnetism: Heritage vs. Evolution) project, spectropolarimetric observations were obtained for a sample of 18 Class I and Flat-Spectrum protostars, providing new constraints on their magnetic and accretion properties.

We present the first measurements of large-scale magnetic fields in Class I protostars derived from this SPIRou campaign and discuss their implications for star–disk interactions. We also analyze accretion diagnostics traced by near-infrared emission lines and explore their connection with the measured magnetic fields. These results provide new insights into the role of magnetism in regulating accretion processes during the embedded protostellar phase.