ar X iv : a st ro - p h / 97 07 22 3 v 1 2 0 Ju l 1 99 7 Neutral carbon in the protoplanetary nebulae CRL 618 and CRL 2688

ar X iv : a st ro - p h / 97 07 27 4 v 1 2 5 Ju l 1 99 7 Nonlinear Pulsations

We review some of the recent advances in nonlinear pulsation theory, but also insist on some of the major extant shortcomings.

The Structure of the Prototype Bipolar Protoplanetary Nebula Crl 2688 (egg Nebula): Broadband, Polarimetric, and H2 Line Imaging with Nicmos on the Hubble Space Telescope

High-resolution near-infrared (1.65–2.1 mm) images and 2 mm polarimetric images of the inner 190.5 # 190.3 region of the bipolar protoplanetary nebula CRL 2688, taken with the newly installed Near-Infrared Camera and Multiobject Spectrometer (NICMOS) aboard the Hubble Space Telescope (HST), are reported. The NICMOS images reveal a wealth of structure also seen in HST Wide Field Planetary Camera...

ar X iv : a st ro - p h / 97 11 24 4 v 1 2 0 N ov 1 99 7 POPULATION SYNTHESIS OF HIGH ENERGY TRANSIENTS RELATIVISTIC BINARY MERGING RATES

ar X iv : a st ro - p h / 97 07 33 5 v 1 3 0 Ju l 1 99 7 26 Al in the local interstellar medium

We estimate the 1.8 MeV luminosity of the Sco-Cen association due to radioactive decay of 26 Al to (4 − 15) 10 −5 ph cm −2 s −1. We propose a low surface brightness , limb brightened bubble for the 1.8 MeV intensity distribution. The detectibility of this distribution with existing γ-ray telescopes is discussed.

ar X iv : a st ro - p h / 97 03 11 6 v 1 1 8 M ar 1 99 7 Neutral atomic carbon in the globules of the Helix

We report detection of the 609 μm P1 → P0 line of neutral atomic carbon in globules of the Helix nebula. The measurements were made towards the position of peak CO emission. At the same position, we obtained high-quality CO(2–1) and CO(2–1) spectra and a 135 × 135 map in CO(2–1). The velocity distribution of C I shows six narrow (1–2 km s) components which are associated with individual globule...