Infrared observations of the star R Cas

We present our JHKLM photometry for R Cas performed during 1988–2000. The pulsation period of R Cas is \(P \approx 429\mathop .\limits^d 6\), with the maximum IR brightness lagging behind the maximum visual brightness by ∼0.2 P. The amplitude of light variations appreciably decreases with increasing wavelength at λ≤3 μm. At λ>3 μm, this decrease virtually ceases. There is a step on the ascending branch of IR JHK brightness. The K-L color index increases linearly with K magnitude: \(K - L = 0.304K + 1\mathop .\limits^m 20\). The color temperature dependence, T_K-L=f(K), is also linear: T_K−L = −622K + 1100 K. In going from minimum to maximum, the K flux (as well as the bolometric flux) from the star and its color temperature T_K-L increase by a factor of ∼2.2 and ∼1.3, respectively.