Investigating the semi-regular light variations of the bright M5 supergiant: α Herculis
Source: Astrophysics and Space Science, Volume 328, Numbers 1-2, July 2010 , pp. 113-117(5)
Abstract:Analysis of over 15 years of V-band and Wing three filter near-IR photometry of the bright M5Ib-II supergiant has been carried out. Wavelet analysis of these data reveals that the star pulsates with several complicated oscillation modes. Different time scales of variability are identified, and with the aid of discrete Fourier analysis, depending on the filter, up to seven significant pulsation modes are identified and their frequencies and amplitudes extracted. The Long Secondary Period (LSP) with a mean period of ∼1343 d has been identified, as well as other periods of the order of ∼125 d. The longer period appears to be attributed to the radial pulsational mode, while the various peaks near ∼125 d appear to arise from stochastically excited p-modes. After removing the light contribution of the 5th magnitude binary companion and calibrating the intermediate-band photometry to the Wing photometric system, TiO (719 nm) and near-IR (B-C) Wing color indices were formed. These indices have been calibrated with T eff, while the Wing-C bandpass (1025 nm) serves as a proxy for bolometric magnitude and was transformed to approximate m bol. Finally, the derivation of the variations in the star’s temperature, luminosity and radius is straightforward.
Document Type: Research Article
Affiliations: 1: Department of Physics, Institute for Advanced Studies in Basic Sciences, Gavazang Road, P.O. Box 45195-1159, Zanjan, Iran, Email: firstname.lastname@example.org 2: Department of Astronomy, Villanova University, 800 Lancaster Ave, Villanova, PA, 19085, USA 3: Department of Physics, Institute for Advanced Studies in Basic Sciences, Gavazang Road, P.O. Box 45195-1159, Zanjan, Iran
Publication date: July 1, 2010