Period increased (3.9696 d. in 1989-1993 Hipparcos data, 3.97204 d. in 2008-2023 AAVSO V data, but the trend reversed and it is decreasing again while the amplitude stopped increasing. Changes in pulsation behaviour over the last century may be related to the binary nature of the system, as they seem to occur near each periastron passage, when the secondary (F6V) comes within 29 stellar radii of the Cepheid in its eccentric orbit with P= 29.433 yr. (2023arXiv230903257T)
Amplitude decrease during the 20th century. Currently, amplitude varies but always below 0.05 mag.
Period is increasing.
3
GCVS Team
VB A (B 8.20m, F3V, 18.3", 218deg); SB1 (Porb = 10969d, E = 0.655 [K.W.Kamper, N.R.Evans, R.W. Lyons, JRAS Can 78, N5, 173, 1984.]). P var. There is a non-linear term in the elements: +1.9877d*10**(-7)*E**2. The amplitude of light and radial velocity variation decreased in 1982. A(V) = 0.04m (1984).
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