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

Abstract

A 16-inch Schmidt-Cassegrain telescope on the campus of Naresuan University of Thailand and several similar-size telescopes in China equipped with CCD cameras were used to observe 14 high amplitude delta Scuti stars: 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, between the years 1999 and 2010. Data were also collected from scientific journals and sources on the Internet for these variable stars. Times of light maximum of these delta Scuti stars were then either determined from the observations or obtained from the literature to analyze the pulsation period variations. For the 14 delta Scuti stars we concluded that 7 stars (BS Aqr, CY Aqr, AD CMi, EH Lib, KZ Hya, BE Lyn and DY Peg) are binary or multiple systems. 10 delta Scuti stars are found with periods increasing with rates between 5.86 × 10 −9 and 2.34 × 10 −6 per year and the other 4 stars (BS Aqr, DY Her, BE Lyn and DY Peg) show periods decreasing with rates of about 10 −9 to 10 −8 per year.

Chemical Composition and Photometry of BE Lyncis

“…Derekas et al (2009) performed radial velocity measurements for BE Lyn for three nights to detect possible binarity or additional pulsational frequencies, and they could not detect any nonradial mode pulsation in the RV curve. Recently, Boonyarak et al (2011) got 156 times of maximum light after adding their own observations, and they argued that BE Lyn is a binary or multiple system. Hence, the binarity of BE Lyn has not yet been completely confirmed.…”

“…We calculated the expected times of maximum light by applying the following equation derived by Boonyarak et al (2011): HJD max ¼ 2; 449; 018:2681 þ 0:09586951 · E:…”

KIC 5950759: a high-amplitude δ Sct star with amplitude and frequency modulation near the terminal age main sequence

“…We note that the amplitude and phase modulation observed in KIC 5950759 are seemingly unique, because phase modulation in such stars appears as jumps rather than smooth variation over time (see e.g. Breger & Pamyatnykh 1998;Boonyarak et al 2011). On the other hand, few HADS stars have been studied using such high quality photometric time series as those provided by the Kepler mission.…”

Time-domain survey of the Galactic anti-center using Nanshan 1m telescope

“…From May 2013, we observed several binaries and variable stars, including YZ Boo (e.g. Boonyarak et al 2011), XX Cyg (e.g., Yang et al 2012), BL Cam (e.g., Fu et al 2008), AN Lyn (e.g., Zhou et al 2006), EH Lib (e.g., Wilson et al 1993). All observations were made through standard Johnson filters.…”