Pulsations and Period Changes of the SX Phoenicis Star DY Pegasi1

Abstract

We present 83 new times of maximum light of the SX Phoenicis (SX Phe) star DY Pegasi (DY Peg), based mainly on our new time-series photometric observations from the years 2004–2008. Together with the times of maximum light in the literature, a comprehensive study of the O - C diagram with the data spanning over seven decades leads to a new general ephemeris formula and the determination of a new value of the updated period 0.072926187( ± 3)d. The available times of maximum light can be well modeled with either a triple linear fit, or a fit concerning a continuously increasing period change combined with the light-time effect of an orbital motion. On the contrary, the decreasing period hypothesis suggested by some previous investigators appears to be rejected. The frequency analyses of the data collected in 2004 and 2006 provide the radial pulsation frequency 13.713 c d -1 and its four harmonics. However, although extra powers were present around the reported secondary frequency 17.8 c d -1 in the Fourier transformations of the new data sets, its signal-to-noise ratios were too low to detect this frequency.

On the period variations of several low declination high amplitude delta Scuti variables

“…The newest research paper of this star was published by Fu et al (2009). They used 396 times of maximum light to study period change of this star.…”

“…Papers have been published about AD CMi (Khokhuntod et al 2007), DY Her (Boonyarak and Jiang 2007), KZ Hya (Fu et al 2008), DY Peg (Fu et al 2009), andVZ Cnc (Boonyarak et al 2009). In this paper we present (O-C) calculations for 14 HADS (GP And, CY Aqr, BS Aqr, YZ Boo, AD CMi, VZ Cnc, EH Lib, DY Her, V927 Her, KZ Hya, BE Lyn, V1162 Ori, DY Peg, and CW Ser) among our monitoring targets by using all times of light maximum available.…”

Discrete Scale Relativity and SX Phoenicis Variable Stars

“…12 The star exhibits a regular radialmode pulsation at a frequency of 13.713 cycles per day, with a relatively large amplitude of 0.2455 magnitudes. 13 In Table 1 the basic physical characteristics of DY Peg are summarized. Given the basic physical properties of DY Peg, we can use Discrete Scale Relativity (DSR) to determine the specific Atomic Scale analogue for this specific Stellar Scale system, and we can identify a very limited set of two specific atomic E-level transitions that could possibly be consistent with a rigorous analogy to the star's pulsation characteristics.…”

“…The two energy-level transitions for Boron that would fit our n and l requirements are the [1s 2 2s 2 5s → 1s 2 2s 2 4s] transition and the [1s 2 2s 2 4p → 1s 2 2s 2 4s] transition. 13 The latter transition has a ∆E of 2776.826 cm -1 , which corresponds to an oscillation frequency (ν) of 8.303…”

“…In fact, our highly unique 4-part prediction is vindicated in a convincing manner. The [1s 2 2s 2 4s → 1s 2 2s 2 3p] transition for Boron is: (1) associated with n ≈ 3, (2) involves a change of l from l = 0 to l = 1, (3) is linked to the fundamental oscillation period 13 through the common 4s E-level, and (4) has a Λp β of 2719.11 sec, which agrees with the predicted period of 2727.65 sec at the 99.7% level.…”