\alpha ^ { 1 } Her is the second closest Asymptotic Giant Branch ( AGB ) star to the Sun , and the variable luminous M5 Ib-II member of a triple stellar system containing G8 III and A9 IV-V components .
However , the mass of this important star was previously uncertain with published values ranging from \sim 2 - 15 M _ { \odot } .
As shown by this study , its fortuitous membership in a nearby resolved triple star system , makes it possible to determine its fundamental properties including its mass and age .
We present over twenty years of VRI photometry of \alpha ^ { 1 } Her as well as Wing intermediate-band near-IR TiO and NIR continuum photometry .
We introduce a new photometry-based calibration technique , and extract the effective temperature and luminosity of \alpha ^ { 1 } Her , in agreement with recent interferometric measures .
We find , T _ { eff } = 3280 \pm 87 K and \log ( L / L _ { \odot } ) = 3.92 \pm 0.14 .

With the MESA code , we calculate a dense grid of evolutionary tracks for Galactic low- to intermediate-mass ( 1.3 to 8 M _ { \odot } ) rotating stars from the pre-main sequence phase to the advanced AGB phase .
We include atomic diffusion and rotation mechanisms to treat the effects of extra elemental mixing .
Based on the observed properties of the \alpha Herculis stars , we constrain the age of the system to lie in the range 0.41 to 1.25 Gyr .
Thus , the mass of \alpha ^ { 1 } Her lies in the range 2.175 \leq M / M _ { \odot } \leq 3.250 .
We compare our model-based age inference with recent tracks of the Geneva and STAREVOL codes , and show their agreement .
In the prescribed mass range for \alpha ^ { 1 } Her , the observed ^ { 12 } C/ ^ { 13 } C and ^ { 16 } O/ ^ { 17 } O ratios are consistent ( within 2 \sigma ) with the ratios predicted by the MESA , Geneva and STAREVOL codes .