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HR 4074: an Emission-Free NRP Twin of the Be Star 28 CMa

  • S. Štefl (a1), Th. Rivinius (a2) and D. Baade (a2)

Extract

In spite of considerable progress in the investigation of rapid line-profile variations (lpv) of Be stars, at least two models still compete in the literature: the rotational modulation, assuming mostly corotating circumstellar structures (Balona, 2000), and nonradial pulsations (Maintz et al. and Rivinius et al., these proceedings). Attempts to explain the lpv of Be stars were often connected with the proto-typical star 28 (ω) CMa (HR 2749 = HD 56139, B2IV-Ve, v sin i = 80 km/s). Štefl et al. (1998) described variability in three line-profile components: in the narrow component of the line core, in the line core itself and in the wings. The Balmer emission of 28 CMa is variable and has always been observed to be at least moderate, mostly strong.

HR 4074 (HD 89890, B3 III, v sin i = 70 km/s) has a different history of its emission activity. From a single spectrogram taken in 1893, Pickering (1898) reported an emission in Hβ. Subsequent observations never confirmed this. If it was not mis-identified by Pickering, HR 4074 would be in the probably longest B-star phase known of any Be star. HR 4074 is very probably not an SPB star - the spectral type is too early, the rotational velocity too high and light variations too low for this classification. Baade (1984) detected rapid lpv with a period P ≈ 2.25 d. Our time series analysis of radial velocity (RV) variations, measured as line modes, and that of full profiles give P = (2.3179 ± 0.0008) d.

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Copyright

References

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Baade, D. 1984, A&A, 134, 105
Baade, D. 1987, in Physics of Be stars, eds. Slettebak, A. & Snow, T., (Cambridge University Press), 361
Balona, L.A. 2000, in ASP Conf. Ser., Vol. 214, The Be Phenomenon in Early-Type Stars, eds. Smith, M., Henrichs, H., & Fabregat, J., 1
Pickering, E.C. 1898, Harvard Circ. No. 224
Rivinius, Th., Baade, D., Štefl, S., et al. 2001, A&A, 369, 1058
Townsend, R.H.D. 1998, MNRAS, 284, 839

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