Non-detection of J1407b in ALMA Band 7 Observations

TL;DR

The study tests whether the 2017 ALMA Band 7 detection near J1407 could be the object responsible for the 2007 eclipse. It employs a second epoch ALMA observation at $\,\sim345$ GHz, with uv-plane concatenation and proper-motion propagation to predict the 2024 position, achieving an rms of $17.5\,\mu{\rm Jy}$ and a beam of $0.12''\times0.07''$. The non-detection at both the 2017 and the projected 2024 locations rules out a dusty object as the eclipse source and disfavors models with thick disks containing grains $>1\,\rm mm$, suggesting the 2017 detection was likely a noise spike or a transient/variable source. This work demonstrates the power of multi-epoch, high-resolution millimeter observations and precise proper-motion tracking to test eclipse-origin hypotheses for J1407.

Abstract

We report on ALMA Band 7 continuum observations towards the star 1SWASP J140747.93-394542.6 taken in mid 2024. These observations were a follow-up of a previous detection of an emission source in the J1407 field of view at an unexpected position in 2017. Proper motion analysis indicated that if this were the object responsible for the 2007 eclipse of J1407, it would be detectable at a new position, but still within an ALMA field of view in 2024. Here we present the non-detection of emission in the ALMA field of view (to a 1σ upper limit of 17.5 μJy),at both the 2017 position, and the position expected from proper motions. We place upper limits on a source at the proper motion corrected expected location in this 2024 data, and rule out the possibility of a dusty object being responsible for the 2007 eclipse

Figures (1)

• Figure 1: Multi-epoch ALMA observations of the J1407 area. There was a $\sim4\sigma$ 345 GHz continuum detection in the 2017 epoch observations that does not seem to persist to the 2024 observations, despite the two observations having similar beams and noise levels.