THE BOOTIS STAR HD A CANDIDATE FOR THE EXPLORATORY PROGRAMME Ernst Paunzen IfA, University Vienna

What are  Bootis stars? F late B to early F-type (from H - lines) non-magnetic dwarfs (LK V) Population I F solar abundant: C, N, O and S other metals underabundant (100 times), exception of Na F ZAMS to TAMS F 2% of all stars in parameter range

All about HD ( I) F Investigated in detail F Basic parameters: V = 5.79,  = ,  = (2000) (b - y) = , m 1 = 0.165, c 1 = 1.002,  T(eff) = 9280(80) K, log g = 4.26(5) dex v sin i = 90(3) kms -1, d = 59(3) pc, R V = +12 kms -1 M V = 1.86(14) log L/L  = 1.26(6)

All about HD ( II) F No signs of shell or IR excess F IUE data confirm membership F Near ZAMS (a few 10 8 yr)  2.1 M 

Variability of HD F Photometry: SAAO: 8 nights, 24 hours of data, 47.37, 45.06, 43.72, c/d 30.40, 31.96, 32.94, min peak/peak 5.4, 4.8, 4.4, 3.8 mmag  Spectroscopy: CFHT: 12 spectra c/d (13.94 min)  1.2% amplitude

Pulsation and Diffusion Opacity changes Frequency differences of radial modes for LB abundances vs solar, if LB diffuses down to logT=4.4, 5.0 and 5.8 (+, o,  ) n Turcotte (2002)

Why MOST? F Low ampl. components of frequ.spectrum needed F higher frequency(-ies) in spectral line profiles  noise reduction needed  MOST  slightly outside empirical  Scuti strip, non-solar abundances: surface or global feature?  asteroseismic techniques  MOST  competing Bootis theories  MOST