Publication details
The pulsation properties of lambda bootis stars I. the southern TESS sample
| Authors | |
|---|---|
| Year of publication | 2020 |
| Type | Article in Periodical |
| Magazine / Source | Monthly Notices of the Royal Astronomical Society |
| MU Faculty or unit | |
| Citation | |
| Web | https://academic.oup.com/mnras/article-abstract/495/2/1888/5834555 |
| Doi | http://dx.doi.org/10.1093/mnras/staa1271 |
| Keywords | asteroseismology; stars: chemically peculiar; stars: oscillations |
| Description | We analyse TESS light curves for 70 southern lambda Boo stars to identify binaries and to determine which of them pulsate as delta Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of lambda Boo stars pulsate as delta Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the lambda Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 lambda Boo stars have 2-min TESS data, reliable temperatures and luminosities, and delta Sct pulsation. We use Petersen diagrams (period ratios), echelle diagrams, and the periodluminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their echelle diagrams. We use stellar evolutionmodels to determine statistically that the lambda Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of Z = 0.01 than at Z = 0.001. The TESS observations reveal the great potential of asteroseismology on lambda Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the lambda Boo phenomenon. |