The ASAS-SN catalogue of variable stars VI: An all-sky sample of d Scuti stars

Abstract

We characterize an all-sky catalogue of ~8400 d Scuti variables in ASAS-SN, which includes ~3300 new discoveries. Using distances from Gaia DR2, we derive period-luminosity relationships for both the fundamental mode and overtone pulsators in the WJK, V, Gaia DR2 G, J, H, Ks, andW1 bands.We find that the overtone pulsators have a dominant overtone mode, with many sources pulsating in the second overtone or higher order modes. The fundamental mode pulsators have metallicity-dependent periods, with log10(P)~-1.1 for [Fe/H] 0, which leads to a period-dependent scale height. Stars with P >0.100 d are predominantly located close to the Galactic disc (|Z| < 0.5 kpc). The median period at a scale height of Z ~ 0 kpc also increases with the Galactocentric radius R, from log10(P) ~ -0.94 for sources with R > 9 kpc to log10(P) ~ -0.85 for sources with R < 7 kpc, which is indicative of a radial metallicity gradient. To illustrate potential applications of this all-sky catalogue, we obtained 30 min cadence, image subtraction TESS light curves for a sample of 10 fundamental mode and 10 overtone d Scuti stars discovered by ASAS-SN. From this sample, we identified two new d Scuti eclipsing binaries, ASASSN-V J071855.62-434247.3 and ASASSN-V J170344.20-615941.2 with short orbital periods of Porb = 2.6096 and 2.5347 d, respectively.