ALMA and VLA Observations of the HD 141569 System

Abstract

We present VLA 9 mm (33 GHz) observations of the HD 141569 system from semester 16A. The observations achieve a resolution of 0.25 arcsec ($\sim 28$ au) and a sensitivity of $4.7\mu \mathrm{Jy}\mathrm{bea}{\mathrm{m}}^{-1}$. We find (1) a $52\pm 5\mu$Jy point source at the location of HD 141569A that shows potential variability, (2) the detected flux is contained within the SED-inferred central clearing of the disc meaning the spectral index of the dust disc is steeper than previously inferred, and (3) the M dwarf companions are also detected and variable. Previous lower-resolution VLA observations (semester 14A) found a higher flux density, interpreted as solely dust emission. When combined with ALMA observations, the VLA 14A observations suggested the spectral index and grain size distribution of HD 141569's disc was shallow and an outlier among debris systems. Using archival ALMA observations of HD 141569 at 0.87 mm and 2.9 mm we find a dust spectral index of ${\alpha }_{\mathrm{mm}}=1.81\pm 0.20$. The VLA 16A flux corresponds to a brightness temperature of $\sim 5\times 10^6$ K, suggesting strong non-disc emission is affecting the inferred grain properties. The VLA 16A flux density of the M2V companion HD 141569B is $149\pm 9\mu$Jy, corresponding to a brightness temperature of $\sim 2\times 10^8$ K and suggesting significant stellar variability when compared to the VLA14A observations, which are smaller by a factor of $\sim 6$.

Accepted for publication in MNRAS, 8 pages, 6 figures

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• Molecular Gas Clumps from the Destruction of Icy Bodies in the $\beta$ Pictoris Debris Disk
• Investigating the flyby scenario for the HD 141569 system
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• Imaging the 44 AU Kuiper Belt-analogue debris ring around HD 141569A with GPI polarimetry
• The MESAS Project: Long wavelength follow-up observations of Sirius A