Query : 2012A&A...542A..15C

2012A&A...542A..15C - Astronomy and Astrophysics, volume 542A, 15-15 (2012/6-1)

CO observations of water-maser post-asymptotic giant branch stars and detection of a high-velocity outflow in IRAS 15452-5459.


Abstract (from CDS):

Many aspects of the evolutionary phase in which asymptotic giant branch stars (AGB stars) are in transition to become planetary nebulae (PNe) remain poorly understood. An important question is how the circumstellar envelopes of AGB stars switch from spherical symmetry to the axially symmetric structures frequently observed in PNe. In many cases, there is clear evidence that the shaping of the circumstellar envelopes of PNe is linked to the formation of jets/collimated winds and their interaction with the remnant AGB envelope. Because of the short timescale of this evolutionary phase, objects are rare, but their identification provides valuable probes for testing evolutionary models. We observed (sub)millimeter CO rotational transitions with the APEX telescope in a small sample of stars hosting high-velocity OH and water masers. These targets are assumed to have recently left the AGB, as indicated by the presence of winds traced by masers with velocities larger than observed during that phase. We carried out observations of several CO lines, ranging from J=2-1 up to J=7-6. In IRAS 15452-5459, we detect a fast molecular outflow in the central region of the nebula and estimate a mass-loss rate between 1.2x10–4M/yr (assuming optically thin emission) and 4.9x10–4M/yr (optically thick emission). We model the SED of this target taking advantage of our continuum measurement at 345GHz to constrain the emission at long wavelengths. For a distance of 2.5kpc, we estimate a luminosity of 8000L and a dust mass of ∼0.01M. Through the flux in the [CII] line (158µm), we calculate a total mass of about 12M for the circumstellar envelope, but the line is likely affected by interstellar contamination.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - circumstellar matter - submillimeter: stars

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 IRAS 15103-5754 pA? 15 14 18.5363258040 -58 05 20.384225484           ~ 31 0
2 IRAS 15452-5459 pA* 15 49 11.3344710672 -55 08 51.846940176           O-rich 30 0
3 IRAS 18043-2116 OH* 18 07 20.86584 -21 16 12.1116           O-rich 39 0
4 IRAS 18103-1738 OH* 18 13 20.26560 -17 37 16.9896           O-rich 8 0
5 OH 012.8-00.9 OH* 18 16 49.21368 -18 15 01.6560           O-rich 48 0
6 OH 019.2-01.0 OH* 18 29 28.7275536432 -12 37 53.104039788           O-rich 49 0
7 OH 024.7+00.3 OH* 18 35 29.21616 -07 13 10.9740           O-rich 37 0
8 IRAS 19190+1102 pA? 19 21 25.14600 +11 08 41.4708           ~ 23 0

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