An asteroseismic study of the Southern Cephei star ALS 3721

Abstract

We present the results of a new investigation aimed to identify the pulsational characteristics of the Southern β Cephei star ALS 3721. Spectroscopic and multicolour photometric data were acquired at the South African Astronomical Observatory (SAAO), South Africa in 2011. Frequency analysis showed that the oscillations of ALS 3721 could be attributed to the two main frequencies with higher significance. Stellar parameters and projected rotational velocity obtained by the spectra were also used to perform photometric mode identification. In order to determine spherical harmonic degrees (l), a principal method was followed by comparing the observed light amplitude ratios in different passbands with those computed from non-adiabatic pulsation models. In general case, therefore, the spherical harmonic degrees corresponding of the frequencies were found in the expected β Cephei range.

RAPID EVOLUTION OF GSC 03144-595, a NEW TRIPLE-MODE RADIALLY PULSATING HIGH-AMPLITUDE Δ SCUTI

“…In Table 1 we show the frequencies, amplitudes, and phases found in both the 2011 and 2014 observations. All of our frequencies are consistent with those found from the Kepler data by Ulusoy et al (2013). Only modes detected with signal to noise S/N > 4.0 are given (Breger et al 1993).…”

“…We first consider the period ratios for the independent modes. Ulusoy et al (2013) claim that the observed period ratio P 1 /P 0 = 0.763 of GSC 03144-595 differs significantly from the expected value for radial first overtone and fundamental modes. However, there is no accepted lower bound for this period ratio, and several double mode pulsators have been observed to have a similar ratio (Poretti et al 2005).…”

“…Thus we would expect the amplitude of the combination modes involving f 3 to be proportional to the amplitude of the f 3 mode. Ulusoy et al (2013) has reported multi-site observations of GSC 03144-595 from 2011. They argue that the the lowest two independent frequency modes f 1 and f 2 are non-radial, l = 1 modes, and that the identification Frequencies, amplitudes, and phases of pulsation modes of GSC 03144-595 observed in both the V and B filters in the years 2011 and 2014.…”

“…The distance modulus for this star is thus µ = m V −M V = 10.0, suggesting the star is at a distance d = 1, 000 pc. Ulusoy et al (2013) detected a third independent frequency based on ground based observations taken in 2011 and observations taken by the Kepler satellite. They also present ground based spectroscopic observations; by fitting Hα and Hβ lines they estimate that T ef f = 6950 ± 100K and log g = 3.7 ± 0.1.…”

AE Ursae Majoris – a δ Scuti Star in the Hertzsprung Gap

“…Not like the solar-like stars for which many frequencies are detected, most HADS are observed with only the fundamental and the first overtone modes in general (e.g., Balona et al 2012;Ulusoy et al 2013). As a result, the period variation becomes a very important constraint on the model calculation of these stars.…”