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The disrupted molecular envelope of Frosty Leo

Castro-Carrizo, A. and Bujarrabal, V. and Sánchez Contreras, C. and Sahai, R. and Alcolea, J. (2005) The disrupted molecular envelope of Frosty Leo. Astronomy and Astrophysics, 431 (3). pp. 979-991. ISSN 0004-6361.

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[img] Image (GIF) (Figure 1: Processed image from the original one at 0.6 $\mu $m observed by the Hubble Space Telescope (with the wide-band F606W/POLQ filter/polariser; see Sahai et al. 2000), which enphasizes the sharp features of Frosty Leo) - Supplemental Material
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[img] Image (GIF) (Figure 5: Profiles of the emission coming from Frosty Leo for the rotational 12CO transitions ( left) J=2-1, by the PdB interferometer, ( center) J=1-0, by the PdB array, and ( right) 1-0, by the OVRO array) - Supplemental Material
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[img] Image (GIF) (Figure 9: In contours, the average of the intensity predicted by modeling the CO J=2-1 emission, for the velocity ranges shown in the left-upper corner, over the optical image obtained by the HST) - Supplemental Material
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We present maps of CO emission in the protoplanetary nebula Frosty Leo. Observations of the rotational transitions ^(12)CO J=2-1 and 1-0 have been obtained with the IRAM interferometer and the OVRO array. The molecular envelope of Frosty Leo is found to be complex and compact; most of the gas extends ≾6" and shows a structure that is very different to the extended optical nebula. It is composed of a central ring-like structure, whose symmetry axis is inclined ~-40° with respect to the sky plane and expands at speeds of up to ~30 km s^(-1), and high-velocity jets distributed along the symmetry axis of the ring, which reach expansion velocities as high as ~75 km s^(-1). The symmetry axis of the molecular jets in the plane of the sky coincides with the direction of some jet-like features seen in the optical, which are not aligned at all with the main symmetry axis of the optical nebula. The brightness distribution of the ring presents a clumpy structure. We have modeled the spatio-kinematical distribution of, and the excitation conditions in, the molecular envelope. For both transitions, the ^(12)CO emission is found to be very optically thick in the center of the nebula. From our best-fit model, we find that the nebular particle density varies between ~10^5 cm^(-3) and ~10^3 cm^(-3), and that the rotational temperature is very low, ~10 K. The kinematical lifetime of the molecular jets is ~1700 yr, long in comparison with the lifetime of the post-AGB winds of most PPNe. It is very remarkable that the bulk of the gas accelerated during the post-AGB phase of Frosty Leo is located within the central ring, reaching expansion velocities of up to ~30 km s^(-1). The central ring-like distribution of Frosty Leo is probably not the undisrupted remnant of the previous AGB envelope (as found for most PPNe), but its dynamics likely result from multiple post-AGB interactions.

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Additional Information:© ESO 2005. (Received 17 June 2004 / Accepted 19 October 2004) A.C.-C. was supported during the development of this work initially by the Spanish SEEU and the European Social Fund, and later by a Marie-Curie Intra-European Fellowship within the 6th European Community Framework Programme. CSC was supported by the American National Science Foundation Grant No. 9981546 to OVRO. The contribution by VB and JA was funded during this work by the Spanish DGES, under project PB96-0104. RS acknowledges financial support from NASA through Long Term Space Astrophysics grant (No. 399-20-61-00-00) and HST/GO grant (No. GO-06816.01-95A) from the Space Telescope Science Institute. We thank Michael Bremer for his help in the preparation of Fig. 7. We acknowledge the IRAM staff (both at Plateau de Bure and Grenoble) and the OVRO staff for carrying out the observations and the help they provided during the data reduction.
Funding AgencyGrant Number
European Social FundUNSPECIFIED
Marie Curie FellowshipUNSPECIFIED
Dirección General de Educación Superior (DGES)PB96-0104
Subject Keywords:stars: individual: Frosty Leo -- stars: circumstellar matter -- stars: AGB and post-AGB -- radio lines: stars -- stars: mass-loss
Issue or Number:3
Record Number:CaltechAUTHORS:20170408-143254646
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Official Citation:The disrupted molecular envelope of Frosty Leo A. Castro-Carrizo, V. Bujarrabal, C. Sánchez Contreras, R. Sahai and J. Alcolea A&A, 431 3 (2005) 979-991 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75964
Deposited By: 1Science Import
Deposited On:25 Apr 2017 21:46
Last Modified:03 Oct 2019 16:56

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