Variable Blue Straggler Stars in the Open Cluster NGC 6819 Observed in the Kepler “Superstamp” Field

0571209 - ASÚ 2024 RIV US eng J - Journal Article
Guzik, J. A. - Baran, A.S. - Sanjayan, S. - Németh, Péter - Hedlund, A. M. - Jackiewicz, J. - Dauelsberg, L. R.
Variable Blue Straggler Stars in the Open Cluster NGC 6819 Observed in the Kepler “Superstamp” Field.
Astronomical Journal. Roč. 165, č. 5 (2023), č. článku 188. ISSN 0004-6256. E-ISSN 1538-3881
R&D Projects: GA ČR(CZ) GA22-34467S
Institutional support: RVO:67985815
Keywords : Delta Scuti variable stars * asteroseismology * blue straggler stars
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 5.3, year: 2022
Method of publishing: Open access

We present light curves and pulsation frequency analyses derived from custom photometric reductions for five confirmed cluster members-four blue stragglers and one star near the main-sequence turnoff. Two of these stars show a rich spectrum of delta Scuti pulsation modes, with 236 and 124 significant frequencies identified, respectively, while two stars show mainly low-frequency modes, characteristic of gamma Doradus variable stars. The fifth star, a known active X-ray binary, shows only several harmonics of two main frequencies. For the two delta Scuti stars, we use a frequency separation-mean density relation to estimate their mean densities, and then use these values along with their effective temperature to derive their stellar masses and radii. For the two stars showing low frequencies, we searched for period-spacing sequences that may be representative of gravity-mode or Rossby-mode sequences, but found no clear sequences. The common age for the cluster members, considered along with the frequencies, will provide valuable constraints for asteroseismic analyses, and may shed light on the origin of the blue stragglers.
Permanent Link: https://hdl.handle.net/11104/0342483