Observed evolutionary changes in the visual magnitude of the luminous blue variable P Cygni

Details Observed evolutionary changes in the visual magnitude of the luminous blue variable P Cygni Observed evolutionary changes in the visual magnitude of the luminous blue variable P Cygni

Apr 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992a%26a...257..153l&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 257, no. 1, p. 153-162.

Astronomy and Astrophysics

Astrophysics

53

Blue Stars, Stellar Evolution, Stellar Luminosity, Stellar Magnitude, Variable Stars, Hertzsprung-Russell Diagram, Kelvin-Helmholtz Instability, Light Curve, Stellar Color, Stellar Spectrophotometry

Scientific paper

Historical observations of the star P Cygni (B1 Ia(+)) show that the star has steadily increased its visual brightness between 1700 and 1988 by 0.15 +/- 0.02 magn/century. If we assume that the luminosity of the star remained constant, (as predicted by evolutionary tracks of massive stars) the increase in brightness must be due to a steady decrease of the Bolometric Correction and hence of Teff at a rate of 6 +/- 1 percent per century. This is the first time ever that the evolution of a star has been observed in secular photometric variations. The redward evolution of P Cyg in the HR-diagram occurs on a Kelvin-Helmholtz time scale for core-contraction and envelope expansion, but the observed rate of change is a factor of two faster than predicted by the evolutionary tracks. The discrepancy can be explained by either assuming that dynamical effects speed up the post main-sequence evolution of massive stars or that the core mass of the star is smaller than predicted. We briefly discuss the absolute bolometric magnitude of P Cygni during the outbursts in the seventeenth century derived from the observed color and the visual brightness.

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