Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-IR spectroscopy of planetary nebulae precursors   We present near-IR spectroscopy of a sample of 30 IRAS sources recently
identified as late AGB stars, post-AGB stars or early
  PNe. The spectra obtained are centered at various wavelengths covering the
molecular hydrogen v=1-0 S(1) and v=2-1 S(1) emission lines, the recombination
lines of hydrogen Br-gamma, Pf-gamma and Br-alpha, and the CO[v=2-0] first
overtone bandhead at 2.294 microns. As a result of these observations we have
increased from 4 to 13 the total number of proto-PNe detected in molecular
hydrogen. When the molecular hydrogen is fluorescence-excited the detection
rate is found to be directly correlated with the evolutionary stage of the
central star, rather than with the nebular morphology. In contrast,
shocked-excited molecular hydrogen is detected only in strongly bipolar
proto-PNe, sometimes even at an early stage in the post-AGB phase. The strong
correlation of shocked-excited molecular hydrogen emission with bipolarity
found confirms the result previously reported by Kastner et al. (1996) in
evolved PNe. However, our results show that this correlation does not exist in
the case of fluorescence-excited molecular hydrogen.

32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat