Jean Racine, Life and Legend

First observations of W Virginis stars with K2: detection of period doubling

“…To investigate the variability types and physical parameters of the stars, we decided to construct colour-magnitude diagrams (CMD) for them. Although M80-V1 is a member of the globular cluster, it lies at the outskirts of M80, and pulsates with a long period, so previous works either did not cover it or could not determine the average colour and brightness of the star (Harris & Racine 1974;Alcaino et al 1998;Piotto et al 2002). The work of Harris & Racine (1974) used the values determined by Kwee (1968), and we found colour measurements for M80-V1 in the APASS (AAVSO Photometric All-Sky Survey) catalog too.…”

“…Although M80-V1 is a member of the globular cluster, it lies at the outskirts of M80, and pulsates with a long period, so previous works either did not cover it or could not determine the average colour and brightness of the star (Harris & Racine 1974;Alcaino et al 1998;Piotto et al 2002). The work of Harris & Racine (1974) used the values determined by Kwee (1968), and we found colour measurements for M80-V1 in the APASS (AAVSO Photometric All-Sky Survey) catalog too. We identified 7 stars that are present both in the APASS database and in the survey of Alcaino et al (1998) and have no close, bright neighbours, and thus can be used to crossmatch the two data sets.…”

“…Nevertheless, we detected considerable differences between the two measurements. We shifted the latter data set to the APASS one (by adding 0.32 and 0.44 mag to the B and V measurements), because the older, photoelectric data of Harris & Racine (1974) agreed with the APASS brightnesses, and because Alcaino et al (1998) did not use standard stars from this field but relied on transformations obtained from other observations that could be the source of further uncertainties. We then transformed the apparent magnitudes and colours to absolute V magnitudes and dereddened (B −V )0 values.…”