Poster Abstracts - Kepler - NASA

POSTER ABSTRACTSP0805. POSTER SESSION IIAre the constant Kepler A-stars chemically peculiar? Simon. J. Murphy, Jeremiah Horrocks Institute, Universityof Cenral Lancashire, Preston, PR1 2HE, UK; email: smurphy6@uclan.ac.ukIntroduction: The delta Scuti instability strip liesat the junction between the classical Cepheid instabilitystrip and the main sequence. Amongst the deltaScuti stars in this region lie the rather more constantmetallic-lined (Am) stars. These represent a significantfraction of A stars – up to 50% at A8 [1]. Of the tenknown Am stars in the Kepler field, six are known topulsate [2].Now that it is known that some Am stars do pulsate,we must question whether the constant A-stars allhave Am spectra. Given that 70% of non-chemicallypeculiar stars are delta Scuti stars and are thereforevariable (based on pre-Kepler photometric sensitivitylevels; [3]), we might expect almost all of the nonvariablestars in the Kepler field of view to be chemicallypeculiar.The unprecedented precision of the Kepler spacecraftallows stars to be studied photometrically at themicro-magnitude variability level. Stars that are constantat this level are unusual indeed. Pulsation, spotsand activity all contribute to total variability, hencethese A-stars are probably the only stars in the HRdiagramthat are truly constant.Method: This study uses Q3 long-cadence Keplerdata to investigate nine of the most constant A-stars inthe Kepler field of view. This is accompanied by spectroscopicobservations to investigate atmospheric parametersand chemical peculiarity.References: [1] Smalley B. et al., 2011, A&A, 535,A3+ [2] Balona L. A. et al., 2011, MNRAS, 396 [3]Turcotte S., Richer J., Michaud G., Christensen-Dalsgaard J., 2000, A&A, 360, 603.2011 Kepler Science Conference - NASA Ames Research Center 199