Deborah Mitchell

Abell 41: shaping of a planetary nebula by a binary central star★

We present the first detailed spatiokinematical analysis and modelling of the planetary nebula Abell 41, which is known to contain the well-studied close-binary system MT Ser. This object represents an important test case in the study of the evolution of planetary nebulae with binary central stars as current evolutionary theories predict that the binary plane should be aligned perpendicular to the symmetry axis of the nebula. Deep narrow-band imaging in the light of [N II] 6584 A, [O III] 5007 A and [S II] 6717+ 6731 A, obtained using ACAM on the William Herschel Telescope, has been used to investigate the ionization structure of Abell 41. Long-slit observations of the Hα and [N II] 6584 A emission were obtained using the Manchester Echelle Spectrometer on the 2.1-m San Pedro M´ artir Telescope. These spectra, combined with the narrow-band imagery, were used to develop a spatiokinematical model of [N II] 6584 A emission from Abell 41. The best-fitting model reveals Abell 41 to have a waisted, bipolar structure with an expansion velocity of ∼40 km s −1 at the waist. The symmetry axis of the model nebula is within 5 ◦ of perpendicular to the orbital plane of the central binary system. This provides strong evidence that the close-binary system, MT Ser, has directly affected the shaping of its nebula, Abell 41. Although the theoretical link between bipolar planetary nebulae and binary central stars is long established, this nebula is only the second to have this link, between nebular symmetry axis and binary plane, proved observationally.

Ultrasound and radionuclide scans—poor indicators of liver damage in patients treated with methotrexate

Ultrasound and radionuclide scans of the liver were compared with biopsy histology as a means of assessing hepatotoxicity in 49 psoriatic patients receiving methotrexate, Ultrasound failed to identify any of the 12 patients with hepatic fibrosis or cirrhosis, Radionuclide scans in one out of three patients with cirrhosis, and five out of nine patients with libmsis, were reported as normal. Neither method can reliably replace liver biopsy in detecting significant methotrexate‐induced hepatotoxicity in psoriatic patients.

The structures and kinematics of planetary nebulae with close-binary central stars

A programme is currently underway to study the structures and kinematics of planetary nebulae known to contain close-binary central stars. Images and high-resolution spectroscopy are presented of the collimated nebula Abell 63 and the ring-like nebula Sp 1. A spatio-kinematical model shows that Abell 63 has a tube-like structure, which has the same inclination as the orbital plane of the central binary system. Kinematic data reveal that Sp 1 is not a hollow sphere, but a tube-like nebula viewed pole-on.