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

Gledhill, T.M., Forde, K.P., Lowe, K.T.E., 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: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 ?m 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 ?m 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
DOI/Identification number: 10.1111/j.1365-2966.2010.17779.x
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: 29 May 2019 15:54 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50086 (The current URI for this page, for reference purposes)
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