NO X-RAYS FROM THE VERY NEARBY TYPE Ia SN 2014J: CONSTRAINTS ON ITS ENVIRONMENT

Deep X-ray observations of the post-explosion environment around the very nearby Type Ia SN 2014J ( d L = 3.5 Mpc) reveal no X-ray emission down to a luminosity L x < 7 × 10 36 erg s −1 (0.3–10 keV) at δ t ∼ 20 days after the explosion. We interpret this limit in the context of inverse Compton emission from upscattered optical photons by the supernova shock and constrain the pre-explosion mass-loss rate of the stellar progenitor system to be (for wind velocity v w = 100 km s −1 ). Alternatively, the SN shock might be expanding into a uniform medium with density n CSM < 3 cm −3 . These results rule out single-degenerate (SD) systems with steady mass loss until the terminal explosion and constrain the fraction of transferred material lost at the outer Lagrangian point to be ⩽1%. The allowed progenitors are (1) white dwarf–white dwarf progenitors, (2) SD systems with unstable hydrogen burning experiencing recurrent nova eruptions with recurrence time t < 300 yr, and (3) stars where the mass loss ceases before the explosion.