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Start Over Descriptor "stars : oscillations" Publisher edp sciences
2 results on '"stars : oscillations"'

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

Subjects
stars : variables : general, HD-168625, LONG-TERM PHOTOMETRY, stars : early-type, stars : individual : HD 168625, ESO, stars : oscillations, ALPHA-CYGNI VARIABLES, STARS, stars : individual : HD 168607
Abstract

Stromgren differential photometry of I-ID 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 I-ID 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 a Cygni-type microvariability, no other signs of ultrashort-periodic variability has been observed.

Published
1999

2. The field high-amplitude SX Phoenicis variable BL Camelopardalis: results from a multisite photometric campaign

Author

Physics, Rodriguez, E., Fauvaud, S., Farrell, J. A., Zhou, A. Y., Sareyan, J. P., Lopez-Gonzalez, M. J., Dupret, M. A., Grigahcene, A., de Ridder, J., Klingenberg, G., Wolf, M., Van Cauteren, P., Lampens, P., Martinez, D., Casanova, V. M., Aceituno, F. J., Helvaci, M., Hintz, E. G., Kral, L., Fumagalli, F., Simonetti, John H., Granslo, B. H., Kotkova, L., Santacana, G., Michelet, J., Fauvaud, M., Vugnon, J. M., Sadsaoud, H., Aliouane, A., Grigahcene, Z. C., Martin-Ruiz, S., Amado, P. J., Suarez, J. C., Moya, A., Kucakova, H., Kocian, R., Truparova, B., Avdibegtovic, A., Blazek, M., Kliner, J., Zasche, P., Vilasek, M., Bartosikova, S., Yasarsoy, B., Ulusoy, C., Graham, K. A., Nicholson, M. P., Trondal, O., Yesilyaprak, C., Coker, D., Physics, Rodriguez, E., Fauvaud, S., Farrell, J. A., Zhou, A. Y., Sareyan, J. P., Lopez-Gonzalez, M. J., Dupret, M. A., Grigahcene, A., de Ridder, J., Klingenberg, G., Wolf, M., Van Cauteren, P., Lampens, P., Martinez, D., Casanova, V. M., Aceituno, F. J., Helvaci, M., Hintz, E. G., Kral, L., Fumagalli, F., Simonetti, John H., Granslo, B. H., Kotkova, L., Santacana, G., Michelet, J., Fauvaud, M., Vugnon, J. M., Sadsaoud, H., Aliouane, A., Grigahcene, Z. C., Martin-Ruiz, S., Amado, P. J., Suarez, J. C., Moya, A., Kucakova, H., Kocian, R., Truparova, B., Avdibegtovic, A., Blazek, M., Kliner, J., Zasche, P., Vilasek, M., Bartosikova, S., Yasarsoy, B., Ulusoy, C., Graham, K. A., Nicholson, M. P., Trondal, O., Yesilyaprak, C., and Coker, D.

Abstract

Context. BL Cam is an extreme metal-deficient field high-amplitude SX Phe-type variable where a very complex frequency spectrum is detected, with a number of independent nonradial modes excited, unusual among the high-amplitude pulsators in the Lower Classical Instability Strip. Aims. An extensive and detailed study has been carried out to investigate the pulsational content and properties of this object. Methods. The analysis is based on 283 h of CCD observations obtained in the Johnson V filter, during a long multisite photometric campaign carried out along the Northern autumn-winter of 2005-2006. Additionally, multicolour BI photometry was also collected to study the phase shifts and amplitude ratios, between light curves obtained in different filters, for modal discrimination of the main excited modes. Results. The detailed frequency analysis revealed a very rich and dense pulsational content consisting of 25 significant peaks, 22 of them corresponding to independent modes: one is the already known main periodicity f(0) = 25.5765 cd(-1) (Delta V = 153 mmag) and the other 21 are excited modes showing very small amplitudes. Some additional periodicities are probably still remaining in the residuals. This represents the most complex spectrum ever detected in a high-amplitude pulsator of this type. The majority of the secondary modes suspected from earlier works are confirmed here and, additionally, a large number of new peaks are detected. The amplitude of the main periodicity f(0) seems to be stable during decades, but the majority of the secondary modes show strong amplitude changes from one epoch to another. The suspected fundamental radial nature of the main periodicity of BL Cam is confirmed, while the secondary peak f(1) = 25.2523 cd(-1) is identified as a nonradial mixed mode g(4) with l = 1. The radial double-mode nature, claimed by some authors for the main two frequencies of BL Cam, is not confirmed. Nevertheless, the frequency f(6) = 32.6464 cd(-1) could

Published
2007

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