Doppler imaging of BD+22 degrees 4409 (LO Peg) using least-squares deconvolution

We present maximum-entropy reconstructions of the rapidly rotating dwarf si ngle star BD+22 degrees 4409 (LO Peg) from observations at the William Hers chel Telescope in 1993 August. Since this star is too faint to use the conv entional single- or three-line Doppler imaging methods, we make use of the novel method of least-squares deconvolution, which utilizes the large numbe r of photospheric lines in an echelle spectrum to produce a single high sig nal-to-noise ratio profile. The star-spot distributions from the image reconstructions show cool featur es at both high and low latitudes, in contradiction to recent theoretical p redictions of the dynamo behaviour in rapidly rotating stars. Cross-correla tion of the images from consecutive nights shows a good correlation from th e small-scale structures, but no evidence of surface differential rotation. From the cross-correlation of the high-latitude spot we are able to reject the period of 9.22 h of Jeffries et al. in favour of their preferred perio d of 10.17 h, confirming the result of Robb & Cardinal.