2004MNRAS.350L...9E

We present UKIRT UIST spectra of Sakurai's Object (= V4334 Sgr) showing CO fundamental-band absorption features around 4.7 µm. The line centres are at a heliocentric radial velocity of -170±30 km/s. The number and relative strengths of the lines indicate a CO gas temperature of 400±100 K and a CO column density of 7⁺³_–2x 10¹⁷/cm2. The gas was moving away from the central star at an average speed of ∼290±30 km/s in 2003 September. The lines appeared sometime between mid-1999 (well after the opaque dust shell formed) and mid-2000, and may have been somewhat more blueshifted initially than they are now. The observed CO velocity and temperature indicate the continued presence of a fast wind in the object, previously seen in the He i 1.083-µm line beginning just prior to massive dust formation, and more recently in atomic and ionized lines. The dust continuum is consistent with a temperature of 350±30 K, indicating continued cooling of the shell. The similar CO temperature suggests that the bulk of the CO absorption occurs just outside the dust continuum surface.