Physical conditions in the Protoplanetary Nebula CRL 618 derived from observations of vibrationally excited HCCCN

Abstract

We used the Effelsberg 100m and IRAM 30m telescopes to observe vibrationally excited cyanoacetylene (HCCCN) in several rotational transitions toward the proto-planetary nebula CRL618. Lines from 9 different vibrationally excited states with energies ranging up to 1600 K above ground were detected. The lines show P Cygni profiles indicating that the HCCCN emission originates from an expanding and accelerating molecular envelope. The HCCCN rotational temperature varies with velocity, peaks at 520 K, 3 km/s blue-shifted from the systemic velocity and decreases with higher blueshift of the gas. The column density of the absorbing HCCCN is 3-6 x 1E17 cm^2. We modeled spectra based on spherical models of the expanding envelope which provide an excellent fit to the observations, and discuss the implications of the models. Additionally, lines from 13C substituted cyanoacetylene were observed. They can be used to constrain the 12C/13C ratio in this source to 10+-2.

arXiv comment27 pages, 9 figures, to appear in ApJ

References in corpus (4)

• Dusty winds: I. Self-similar solutions
• O-bearing Molecules in Carbon-rich Proto-Planetary Objects
• CO Isotopes in Planetary Nebulae
• Infrared Imaging of Late-Type Stars

Cited by in corpus (17)

• Rotational Excitation of HC_3N by H_2 and He at low temperatures
• High mass star formation in the infrared dark cloud G11.11-0.12
• The observed chemical structure of L1544
• The slowly expanding envelope of CRL618 probed with HC3N rotational ladders
• Detection of HCN Direct l-Type Transitions Probing Hot Molecular Gas in the Proto-Planetary Nebula CRL 618
• Rotational and high-resolution infrared spectrum of HC${}_3$N: global ro-vibrational analysis and improved line catalogue for astrophysical observations
• A pilot search for mm-wavelength recombination lines from emerging ionized winds in pre-planetary nebulae candidates
• Submillimeter Array Observation of the Proto-Planetary Nebula CRL 618 in the CO J=6-5 Line
• Planck intermediate results. XVIII The millimetre and sub-millimetre emission from planetary nebulae
• Mapping the Central Region of the PPN CRL 618 at Sub-arcsecond Resolution at 350 GHz
• Rotational spectra of isotopic species of methyl cyanide, CH${}_3$CN, in their $v_8=1$ excited vibrational states
• Detection of CI line emission towards the oxygen-rich AGB star omi Cet
• The molecular envelope of CRL 618: A new model based on Herschel/HIFI observations
• Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC${}_5$N
• Extensive ro-vibrational analysis of deuterated-cyanoacetylene (DC${}_3$N) from millimeter-wavelengths to the infrared domain
• Rotational spectroscopy of singly ${}^{13}$C substituted isotopomers of propyne and determination of a semi-empirical equilibrium structure
• Detection of 4765 MHz OH Emission in a Pre-Planetary Nebula -- CRL 618