Confirmation of eclipses in HR 7940 (HD 197770), a reddened B2 III star

Geoffrey C. Clayton, University of Colorado Boulder


It has been confirmed that HR 7940 (HD 197770) is an eclipsing binary. The best period, using data with a 14 year baseline, is 99d.76 ± 0d.04 with an epoch of primary minimum of HJD 2441856.25 ± 0.25. Assuming this period, six primary and four secondary eclipses have been observed. The eclipse duration is ≤ 1d.5. The primary and secondary eclipse depths are similar (ΔV ∼ 0.05). Better phase coverage is needed to determine the parameters of the eclipsing-binary system. The nature of HR 7940 is of interest because the line of sight toward this star is important to studies of the interstellar medium. In particular, it is thought to show a polarized 2175 Å bump.