We present 2-2.4 µm integral field spectroscopy of a sample of hot post-AGB stars with early-B spectral types, using the NIFS instrument on Gemini North. These stars are just beginning to ionize their immediate environments and turn into planetary nebulae (PNe). We use molecular hydrogen emission lines together with hydrogen and helium recombination lines to explore the distribution of molecular and atomic gas and the extent of the developing ionized region. We see a range of evolutionary stages: IRAS 18062+2410 and IRAS 18379-1707 have recently developed compact and unresolved regions of photoionized H within axisymmetric molecular envelopes, with the former object increasing its Brγ flux by a factor of 5.3 in 14 years; IRAS 22023+5249 and IRAS 20462+3416 have extended Brγ nebulae and in the latter object only weak H 2 emission remains; IRAS 19336-0400 is at a more advanced stage of PN formation where H 2 is mostly dissociated and we see structure in both the H and He recombination line nebulae. IRAS 19200+3457 is the only object not to show the He I line at 2.058 µm and is probably the least evolved object in our sample; the H 2 emission forms a ring around the star and we suggest that this object may be a rare example of a "round" pre-PN in transition to a "round" PN.

We report the identification of LSR J0745+2627 in the United Kingdom InfraRed Telescope Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) as a cool white dwarf with kinematics and age compatible with the thick-disk/halo population. LSR J0745+2627 has a high proper motion (890 mas/yr) and a high reduced proper motion value in the J band (H J = 21.87). We show how the infrared-reduced proper motion diagram is useful for selecting a sample of cool white dwarfs with low contamination. LSR J0745+2627 is also detected in the Sloan Digital Sky Survey (SDSS) and the Wide-field Infrared Survey Explorer (WISE). We have spectroscopically confirmed this object as a cool white dwarf using X-Shooter on the Very Large Telescope. A detailed analysis of its spectral energy distribution reveals that its atmosphere is compatible with a pure-H composition model with an effective temperature of 3880 ± 90 K. This object is the brightest pure-H ultracool white dwarf (T eff < 4000 K) ever identified. We have constrained the distance (24-45 pc), space velocities and age considering different surface gravities. The results obtained suggest that LSR J0745+2627 belongs to the thick-disk/halo population and is also one of the closest ultracool white dwarfs.

We present K-band integral field spectroscopy of the bipolar post-asymptotic giant branch (post-AGB) object IRAS 18276−1431 (OH 17.7−2.0) using SINFONI on the VLT. This allows us to image both the continuum and molecular features in this object from 1.95 to 2.45 µm with a spatial resolution down to 70 mas and a spectral resolution of ∼5000. We detect a range of H 2 rovibrational emission lines which are consistent with shock excitation in regions of dense (∼10 7 cm −3 ) gas with shock velocities in the range of 25-30 km s −1 . The distribution of H 2 emission in the bipolar lobes suggests that a fast wind is impinging on material in the cavity walls and tips. H 2 emission is also seen along a line of sight close to the obscured star as well as in the equatorial region to either side of the stellar position which has the appearance of a ring with radius 0.3 arcsec. This latter feature may be radially cospatial with the boundary between the AGB and post-AGB winds. The first overtone 12 CO bandheads are observed longward of 2.29 µm with the v = 2-0 bandhead prominently in emission. The CO emission has the same spatial distribution as the K-band continuum and therefore originates from an unresolved central source close to the star. We interpret this as evidence for ongoing mass-loss in this object. This conclusion is further supported by a rising K-band continuum indicating the presence of warm dust close to the star, possibly down to the condensation radius. The redshifted scattered peak of the CO bandhead is used to estimate a dust velocity along the bipolar axis of 95 km s −1 for the collimated wind. This places a lower limit of ∼125 yr on the age of the bipolar cavities, meaning that the collimated fast wind turned on very soon after the cessation of AGB mass-loss.

Some evolved stars in the pre‐planetary nebula phase produce highly collimated molecular outflows that resemble the accretion‐driven jets and outflows from pre‐main‐sequence stars. We show that IRAS 16342−3814 (the Water Fountain Nebula) is such an object and present K‐band integral field spectroscopy revealing a fast (>150 km s−1) bipolar H2 outflow. The H2 emission is shock excited and may arise in fast‐moving clumps, accelerated by the previously observed precessing jet. The total luminosity in H2 is 0.37 L⊙, which is comparable with that of accretion‐powered outflows from Class 0 protostars. We also detect CO overtone bandhead emission in the scattered continuum, indicating hot molecular gas close to the centre, a feature also observed in a number of protostars with active jets. It seems likely that the jet and outflow in IRAS 16342−3814 are powered by accretion on to a binary companion.

We present K-band integral field observations of the circumstellar envelope of the evolved star OH 231.8+4.2. Spatial and spectral information were simultaneously acquired using the Sinfoni integral field unit, with adaptive optics, on the Very Large Telescope. The observations reveal the discovery of H2 emission (1) around the centre of the nebula and (2) located in clumps along the Western side of the Northern lobe, presumably associated with the strong shocks that stimulate the previously reported H-alpha emission at the same location. An observed H2 1-0/2-1S(1) line ratio of 8.3+/-1.9 was calculated for the central field, a value consistent with shock excitation.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter