Multisite campaign on the open cluster M67 - III.   Scuti pulsations in the blue stragglers

Abstract

We have made an asteroseismic analysis of the variable blue stragglers in the open cluster M67. The data set consists of photometric time‐series from eight sites using nine 0.6–2.1 m telescopes with a time‐baseline of 43 d. In two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41 and 26) detected in δ Scuti stars belonging to a stellar cluster, and EW Cnc has the second highest number of frequencies detected in any δ Scuti star. We have computed a grid of pulsation models that take the effects of rotation into account. The distribution of observed and theoretical frequencies shows that in a wide frequency range a significant fraction of the radial and non‐radial low‐degree modes are excited to detectable amplitudes. Despite the large number of observed frequencies we cannot constrain the fundamental parameters of the stars. To make progress we need to identify the degrees of some of the modes from either multicolour photometry or spectroscopy.

A search for solar-like oscillations in K giants in the globular cluster M 4

“…(4) (as opposed to the inverse variance) was also preferred for similar multi-site campaigns by Handler (2003) and Bruntt et al (2007). The final weight was the product of w 1 and w 2 .…”

Variable stars in one open cluster within theKepler/K2-Campaign-5field: M 67 (NGC 2682)

“…Of these 68 variable stars, 25 variable stars have already been classified in other photometric works (Gilliland et al 1991;Stassun et al 2002;Sandquist & Shetrone 2003a,b;Stello et al 2006Stello et al , 2007Bruntt et al 2007;Pribulla et al 2008;Yakut et al 2009) and/or in the General Catalogue of Variable Stars (GCVS, Samus & Antipin 2013). Other variable stars listed in literature catalogues, but not found in our variable catalogue, are bright objects extremely saturated in our data (even in short exposures) or just outside the Schmidt FOV.…”

“…The OC M 67 has been the subject of many investigations. Among them: the search and study of variable stars (Gilliland et al 1991;Stassun et al 2002;Sandquist & Shetrone 2003a,b;Stello et al 2006Stello et al , 2007Bruntt et al 2007;Pribulla et al 2008;Yakut et al 2009), the determinations of proper motions and memberships (Sanders 1977;Girard et al 1989;Zhao et al 1993;Yadav et al 2008;Geller, Latham & Mathieu 2015), radial velocities Mathieu, Latham & Griffin 1990;Milone 1992;Milone & Latham 1994;Pasquini et al 2011;Geller, Latham & Mathieu 2015), the estimates of cluster parameters (age ∼4 Gyr, distance <1 kpc, metallicity [Fe/H]∼0, E(B − V) ∼ 0.05; Janes & Smith 1984;Nissen, Twarog & Crawford 1987;Demarque, Green & Guenther 1992;Montgomery, Marschall & Janes 1993;Carraro et al 1994;Fan et al 1996;Grocholski & Sarajedini 2003;VandenBerg & Stetson 2004;Sandquist 2004;Randich et al 2006;Balaguer-Núñez, Galadí-Enríquez & Jordi 2007;Taylor 2007;Pasquini et al 2008;Sarajedini, Dotter & Kirkpatrick 2009;Pancino et al 2010;Jacobson, Pilachowski & Friel 2011), the search for exoplanets candidates Brucalassi et al 2014), and the dynamical studies (Bellini et al 2010a;…”

On the use of rotational splitting asymmetries to probe the internal rotation profile of stars: Application to β Cephei stars

“…The study of radial differential rotation has also been used for the asteroseismic studies, e.g. Casas (2006, 2009), Fox Machado (2006, Bruntt et al (2007aBruntt et al ( , 2007b; Suárez et al (2005a), ; Suárez et al (2007), for δ Scuti stars, Rodríguez et al (2006aRodríguez et al ( , 2006b), Uytterhoeven et al (2008), Moya et al (2005), Suárez et al (2005b), for γ Doradus stars, or Suárez et al (2009) …”