Multisite campaign on the open cluster M67. III. Delta 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 meter telescopes with a time baseline of 43 days. In two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41 and 26) detected in delta Scuti stars belonging to a stellar cluster, and EW Cnc has the second highest number of frequencies detected in any delta 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 show 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 either from multi-colour photometry or spectroscopy.

15 pages, 14 figs, one appendix. Part three in a series of papers describing results from an extensive multi-site campaign on the open cluster M67

References in corpus (7)

• Acoustic oscillations of rapidly rotating polytropic stars. II. Effects of the Coriolis and centrifugal accelerations
• The blue stragglers formed via mass transfer in old open clusters
• Multisite campaign on the open cluster M67. II. Evidence for solar-like oscillations in red giant stars
• Amplitude variability or close frequencies in pulsating stars? The Delta Scuti star FG Vir
• A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis
• Multi-site campaign on the open cluster M67. I. Observations and photometric reductions
• Asteroseismology with the WIRE satellite. I. Combining Ground- and Space-based Photometry of the Delta Scuti Star Epsilon Cephei

Cited by in corpus (9)

• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• Polaris the Cepheid returns: 4.5 years of monitoring from ground and space
• A PSF-based approach to Kepler/K2 data - III. Search for exoplanets and variable stars within the open cluster M 67 (NGC 2682)
• MOST satellite photometry of stars in the M67 field: Eclipsing binaries, blue stragglers and delta-Scuti variables
• UOCS.VI. UVIT/AstroSat detection of low-mass white dwarf companions to 4 more blue stragglers in M67
• A search for solar-like oscillations in K giants in the globular cluster M4
• Photometric variability of blue straggler stars in M67 with TESS and K2
• A spectroscopic study of the blue stragglers in M67
• Variable Blue Straggler Stars in Open Cluster NGC 6819 Observed in the Kepler 'Superstamp' Field