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 $a^{\prime }=27.49_{-1.65}^{+3.90}$~km and $b^{\prime }=14.33_{-2.69}^{+2.37}$~km (position angle $95.3_{-2.7}^{+4.9}$ deg), giving an area-equivalent diameter $D_{\mathrm{eq}}=39.86_{-1.66}^{+2.06}$~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 $H_o=11.29_{-0.03}^{+0.02}$~mag ($G_{1,o}=0.94_{-0.05}^{+0.03}$, $G_{2,o}=0.01\pm 0.01$), 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.

arXiv comment16 pages, 8 figures, 4 tables, submitted to A&A