Size, Albedo, and Taxonomy of Asteroid (1201) Strenua from Stellar Occultation and ATLAS Photometry

Abstract

Context. A multi-chord stellar occultation by (1201) Strenua observed on 26 April 2026 is combined with ATLAS $c$- and $o$-band photometry. Aims. We aim to determine the size and geometric albedo of Strenua and reassess its taxonomic classification. Methods. Four positive chords from a 47-station campaign across Indonesia were fitted within a Bayesian forward-modeling framework to derive an ellipse cross-section and equivalent diameter. ATLAS photometry was modeled using the $H, G_1, G_2$ phase-function system to determine band-specific absolute magnitudes, converted to $H_{\mathrm{V}}$, and combined with the occultation diameter to calculate geometric albedo and update taxonomy. Results. The chords yield semi-axes $a' = 27.49^{+3.90}_{-1.65}$~km and $b' = 14.33^{+2.37}_{-2.69}$~km (position angle $95.3^{+4.9}_{-2.7}$ deg), giving an area-equivalent diameter $D_{\mathrm{eq}} = 39.86^{+2.06}_{-1.66}$~km. Photometric modeling gives $H_c = 11.50 \pm 0.05$~mag ($G_{1,c} = 0.81 \pm 0.08$, $G_{2,c} = 0.04 \pm 0.02$) and $H_o = 11.29^{+0.02}_{-0.03}$~mag ($G_{1,o} = 0.94^{+0.03}_{-0.05}$, $G_{2,o} = 0.01 \pm 0.01$), yielding $H_{\mathrm{V}} = 11.46 \pm 0.05$~mag. The resulting geometric albedo $p_{\mathrm{V}} = 0.029 \pm 0.003$ places Strenua among the darkest primitive asteroids, securely reclassifying it as P-class and resolving its legacy X-complex ambiguity.