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Astron. Astrophys. 349, 532-536 (1999)

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Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999) *

C. Sterken 1, T. Arentoft 1, H.W. Duerbeck 1 and E. Brogt 2

1 University of Brussels (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
2 University of Groningen, Kapteyn Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands

Received 11 July 1999 / Accepted 3 August 1999


Strömgren differential photometry of HD 168607 and HD 168625 collected during the previous 27 years is analysed. We bring to an end our quarter of a century monitoring of these objects and conclude that HD 168607 shows typical variability of an uneventful LBV, whereas HD 168625 remains to be classified as a variable hypergiant, or a marginally-dormant LBV. The long-term light- and colour behaviour of HD 168607 indicates the possible presence of a very slowly-developing S Dor phase - that is, a bright phase that coincides with redder colours. Besides the [FORMULA] Cygni-type microvariability, no other signs of ultrashort-periodic variability has been observed.

Key words: stars: early-type – stars: individual: HD 168607 – stars: individual: HD 168625 – stars: oscillations – stars: variables: general

* Based on observations obtained at the European Southern Observatory at La Silla, Chile (applications ESO 56D-0249, 58D-0118, 60D-0148, 61D-0128 and 62H-0110)

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© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999