Expanding Envelope of DQ Herculis

Spectrograms in the H alpha line, taken at 8 position angles of the slit, have been measured to determine velocities in the expanding shell around Nova DQ Her 1934. The observed velocities can be represented with a model involving a prolate, axially symmetric ellipsoidal shell with the following equatorial and polar radii and expansion velocities: a=6."27 pm 0.16, b=8."61 pm 0.16, V_E=384 pm 21 km/s and V_P=528 pm 25k m/s. The polar axis of the shell is nearly perpendicular to the line of sight (i=88.^circ5 pm 0.7). A major deviation from this model occurs in the narrow equatorial belt, where the expansion velocity is only V_EB=351 pm 3k m/s. This correlates with the observed shape of the shell which shows a few percent narrowing near the equator. The distance is d=561 pm 19 pc, ie. larger than estimated earlier.