β CMa photosphere pulsation modes observation with VSII.

β CMa is a B1 II-III giant multi mode pulsating variable star with a visual magnitude varying from +1.97 to +2.01, with periods between 3 hours and 4 hours. VERITAS is an array of telescopes designed for high energy astronomy, which in its VSII (Veritas Stellar Intensity Interferometry) mode is used as an Intensity Interferometer with baselines ranging from 35m to 170m, allowing angular measurements at sub-milliarcsecond scale at wavelength 416nm. Beta CMa is observed with VSII for 70+ hours from 2019 to 2025. Based on these observations, we report a preliminary measurement of the angular diameter of Beta CMa's photosphere and a search for modulation at the known pulsation period.