Line-profile Variability from Tidal Flows in Alpha Virginis (spica)

We present the results of high precision, high resolution (R∼68000) optical observations of the short-period (4d) eccentric binary system Alpha Virginis (Spica) showing the photospheric line-profile variability that in this system can be attributed to non-radial pulsations driven by tidal effects. Although scant in orbital phase coverage, the data provide S/N>2000 line profiles at full spectral resolution in the wavelength range ∆λ4000–8500Å, allowing a detailed study of the night-to-night variability as well as changes that occur on ∼2 hr timescale. Using an ab initio theoretical calculation, we show that the line-profile variability can arise as a natural consequence of surface flows that are induced by the tidal interaction. Subject headings: stars: individual (α Vir, Spica) — stars: binaries (including multiple): close — line: profiles — stars: atmospheres — stars: rotation — techniques: spectroscopic