Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998a%26a...335..533p&link_type=abstract
Astronomy and Astrophysics, v.335, p.533-538 (1998)
Astronomy and Astrophysics
Astrophysics
28
Stars: Early Type, Stars: Oscillations, Stars: Variables: Delta Sct
Scientific paper
In this paper we present a further step in applying asteroseismic techniques to the group of lambda Bootis stars which can be characterized as nonmagnetic A to F-type Population I dwarfs with significant (surface) underabundances of Fe-peak elements. Since no conclusive theory explaining the origin of the observed abundance anomalies exists, an extensive photometric survey for pulsation in this group has been initiated. Knowledge about the pulsational properties (most members are located within the classical instability strip) could help to establish constrains about the overall abundance of these stars as well as on the evolutionary status. New photometric observations were carried out for eleven stars. Variability was detected in four stars (e.g. lambda Bootis itself) whereas the remaining seven objects are probably constant. In total, 52 members of this group have been photometrically investigated so far. With 22 pulsating and 30 ``constant'' stars, we derive a ratio of at least 50 % for variable to nonvariable members inside the classical instability strip. This result is based on high quality Hipparcos and new photometric data. The observed log /lineρ//lineρ_&sun; and log P values for the pulsating members are compatible with standard (solar abundant) delta Scuti models supporting the hypothesis that the found abundance anomalies are restricted to the surface only. Otherwise the pulsational properties of this group are not outstanding compared to ``normal'' delta Scuti stars, indicating that the mechanism driving the pulsations is very similar. Based on observations obtained at ESO-La\,Silla, CTIO, SAAO, McDonald Observatory, Instituto Astrofisica Andalucia Observatory and with the Hipparcos satellite
Garrido Rafa
Gelbmann M.
Handler Gerald
Kuenzli M.
Kuschnig Rainer
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