(3200) Phaethon polarimetry in the negative branch: new evidence for the anhydrous nature of the <i>DESTINY</i>+ target asteroid

We report on the first polarimetric study of (3200) Phaethon, target JAXA's DESTINY$^+$ mission, in negative branch to ensure its anhydrous nature and derive an accurate geometric albedo. conducted observations at low phase angles (Sun-target-observer angle, alpha = 8.8-32.4 deg) from 2021 October 2022 January found that Phaethon has a minimum polarization degree $P_{min}$ -1.3 +- 0.1 %, slope h 0.22 0.02 % deg$^{-1}$, inversion angle alpha$_0$ 19.9 0.3 deg. The derived albedo is $p_V$ 0.11 (in range 0.08-0.13). These properties are consistent with chondrites, contradict hydrous chondrites typical cometary nuclei.