Integral field spectroscopy of H2 and CO emission in IRAS 18276-1431: Evidence for ongoing post-AGB mass-loss

Gledhill, T.M. and Forde, K.P. and Lowe, K.T.E. and Smith, Michael D. (2011) Integral field spectroscopy of H2 and CO emission in IRAS 18276-1431: Evidence for ongoing post-AGB mass-loss. Monthly Notices of the Royal Astronomical Society, 411 (3). pp. 1453-1466. ISSN 0035-8711. (doi:https://doi.org/10.1111/j.1365-2966.2010.17779.x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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http://www.dx.doi.org/10.1111/j.1365-2966.2010.177...

Abstract

We present K-band integral field spectroscopy of the bipolar post-asymptotic giant branch (post-AGB) object IRAS 18276−1431 (OH 17.7−2.0) using SINFONI on the VLT. This allows us to image both the continuum and molecular features in this object from 1.95 to 2.45 μm with a spatial resolution down to 70 mas and a spectral resolution of ∼5000. We detect a range of H2 rovibrational emission lines which are consistent with shock excitation in regions of dense (∼107 cm−3) gas with shock velocities in the range of 25–30 km s−1. The distribution of H2 emission in the bipolar lobes suggests that a fast wind is impinging on material in the cavity walls and tips. H2 emission is also seen along a line of sight close to the obscured star as well as in the equatorial region to either side of the stellar position which has the appearance of a ring with radius 0.3 arcsec. This latter feature may be radially cospatial with the boundary between the AGB and post-AGB winds. The first overtone 12CO bandheads are observed longward of 2.29 μm with the v = 2–0 bandhead prominently in emission. The CO emission has the same spatial distribution as the K-band continuum and therefore originates from an unresolved central source close to the star. We interpret this as evidence for ongoing mass-loss in this object. This conclusion is further supported by a rising K-band continuum indicating the presence of warm dust close to the star, possibly down to the condensation radius. The redshifted scattered peak of the CO bandhead is used to estimate a dust velocity along the bipolar axis of 95 km s−1 for the collimated wind. This places a lower limit of ∼125 yr on the age of the bipolar cavities, meaning that the collimated fast wind turned on very soon after the cessation of AGB mass-loss.

Item Type: Article
Uncontrolled keywords: Circumstellar matter, Shock waves, Stars: AGB and post-AGB, Stars: evolution, Stars: individual: IRAS 18276-1431, Stars: individual: OH 17.7-2.0
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Giles Tarver
Date Deposited: 10 Aug 2015 15:52 UTC
Last Modified: 11 Aug 2015 09:08 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50086 (The current URI for this page, for reference purposes)
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