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arXiv · 1808.10254

Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $\nu$ Puppis (B7-8 IIIe)

D. Baade·A. Pigulski·Th. Rivinius·L. Wang·Ch. Martayan·G. Handler·D. Panoglou·A. C. Carciofi·R. Kuschnig·A. Mehner·A. F. J. Moffat·H. Pablo·S. M. Rucinski·G. A. Wade·W. W. Weiss·K. Zwintz
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Abstract

In early-type Be stars, groups of nonradial pulsation (NRP) modes with numerically related frequencies may be instrumental for the release of excess angular momentum through mass-ejection events. Difference and sum/harmonic frequencies often form additional groups. The goal of this study is to find out whether a similar frequency pattern occurs in the cooler third-magnitude B7-8\,IIIe shell star $\nu$ Pup. Time-series analyses are performed of space photometry with BRITE-Constellation (2015, 2016/17, and 2017/18), SMEI (2003--011), and Hipparcos (1989-1993). Two IUE SWP and 27 optical echelle spectra spanning 20 years were retrieved from various archives. The optical spectra exhibit no anomalies or well-defined variabilities. A magnetic field was not detected. All three photometry satellites recorded variability near 0.656 c/d which is resolved into three features separated by ~0.0021 c/d. First harmonics form a second frequency group, also spaced by ~0.0021 c/d. The frequency spacing is very nearly but not exactly equidistant. Variability near 0.0021 c/d was not detected. The long-term frequency stability could be used to derive meaningful constraints on the properties of a putative companion star. The IUE spectra do not reveal the presence of a hot subluminous secondary. $\nu$\,Pup is another Be star exhibiting an NRP variability pattern with long-term constancy and underlining the importance of combination frequencies and frequency groups. The star is a good target for efforts to identify an effectively single Be star.

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D. Baade, A. Pigulski, Th. Rivinius, L. Wang, Ch. Martayan, G. Handler, D. Panoglou, A. C. Carciofi, R. Kuschnig, A. Mehner, A. F. J. Moffat, H. Pablo, S. M. Rucinski, G. A. Wade, W. W. Weiss, K. Zwintz. 2018-08-30. Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $\nu$ Puppis (B7-8 IIIe). https://doi.org/10.1051/0004-6361%2F201834161

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