2023MNRAS.521.3784L

In the framework of the visible NEAs observations survey (ViNOS) that uses several telescopes at the Canary Islands observatories since 2018, we observed two superfast rotator NEAs, 2021 NY₁ and 2022 AB. We obtained photometry and spectrophotometry of both targets and visible spectroscopy of 2022 AB. Light curves of 2021 NY₁ obtained in four different nights between 2021 September 30 and 2021 October 16 return a rotation period P = 13.3449 ± 0.0013 minutes and a light curve amplitude A = 1.00 mag. We found that 2021 NY₁ is a very elongated superfast rotator with an axis ratio a/b ≥ 3.6. We also report colours (g - r) = 0.664 ± 0.013, (r - i) = 0.186 ± 0.013, and (i - z_s) = -0.117 ± 0.012 mag. These are compatible with an S-type asteroid. The light curves of 2022 AB obtained on 2021 January 5 and 2021 January 8 show a rotation period P = 3.0304 ± 0.0008 min, with amplitudes A = 0.52 and A = 0.54 mag. 2022 AB is also an elongated object with axis ratio a/b ≥ 1.6. The obtained colours are (g - r) = 0.400 ± 0.017, (r - i) = 0.133 ± 0.017, and (i - z_s) = 0.093 ± 0.016. These colours are similar to those of the X-types, but with an unusually high (g - r) value. Spectra obtained on 2022 January 12 and 2022 January 14 are consistent with the reported colours. The spectral upturn over the 0.4 - 0.6 $\mu \mathrm{m}$ region of 2022 AB does not fit with any known asteroid taxonomical class or meteorite spectrum, confirming its unusual surface properties.