A non-LTE abundance analysis of the post-AGB star ROA 5701

Thompson, Henry; Keenan, F. P.; Dufton, P. L.; Ryans, R.; Smoker, J. V.

doi:10.1111/j.1365-2966.2006.10257.x

Cited by 6 publications

(26 citation statements)

References 43 publications

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“…García‐Hernández et al 2007a, and references therein). A similar carbon deficiency is also detected in the hot post‐AGB stars in globular clusters (Moehler et al 1998; Jasniewicz et al 2004; Mooney et al 2004; Thompson et al 2006). The only exception to this observational evidence is the field hot post‐AGB star, IRAS 01005+7910, which shows an overabundance of carbon (Klochkova et al 2002).…”

Section: Discussionsupporting

confidence: 66%

High-resolution spectroscopy of the high-velocity hot post-AGB star LS III +52°24 (IRAS 22023+5249)

Sarkar

García-Hernández

Parthasarathy

et al. 2012

Monthly Notices of the Royal Astronomical Society

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The first high‐resolution (R∼ 50 000) optical spectrum of the B‐type star, LS III +52°24, identified as the optical counterpart of the hot post‐asymptotic giant branch (post‐AGB) candidate IRAS 22023+5249 (I22023) is presented. We report the detailed identifications of the observed absorption and emission features in the full wavelength range (4290–9015 Å) as well as the atmospheric parameters and photospheric abundances (under the local thermodynamic equilibrium approximation) for the first time. The nebular parameters (Te, Ne) are also derived. We estimate Teff= 24 000 K, log g= 3.0 and ξt= 7 km s−1, and the derived abundances indicate a slightly metal‐deficient evolved star with C/O < 1. The observed P‐Cygni profiles of hydrogen and helium clearly indicate ongoing post‐AGB mass‐loss. The presence of [N ii] and [S ii] lines and the non‐detection of [O iii] indicate that photoionization has just started. The observed spectral features, large heliocentric radial velocity, atmospheric parameters and chemical composition indicate that I22023 is an evolved post‐AGB star belonging to the old disc population. The derived nebular parameters (Te= 7000 K, Ne= 1.2 × 104 cm−3) also suggest that I22023 may be evolving into a compact, young low‐excitation planetary nebula. Our optical spectroscopic analysis together with the recent Spitzer detection of double‐dust chemistry (the simultaneous presence of carbonaceous molecules and amorphous silicates) in I22023 and other B‐type post‐AGB candidates may point to a binary system with a dusty disc as the stellar origin common to the hot post‐AGB stars with O‐rich central stars.

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Section: Discussionsupporting

confidence: 66%

High-resolution spectroscopy of the high-velocity hot post-AGB star LS III +52°24 (IRAS 22023+5249)

Sarkar

García-Hernández

Parthasarathy

et al. 2012

Monthly Notices of the Royal Astronomical Society

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“…Non‐LTE model atmosphere grids, calculated with tlusty and synspec (Hubeny 1988; Hubeny & Lanz 1995; Hubeny et al 1998), have been used to derive atmospheric parameters. The methods involved are discussed in, for example, Ryans et al (2003), Hunter et al (2005), Thompson et al (2006, 2007) and Trundle et al (2007), whilst greater detail about the grids may be found in Dufton et al (2005) and at http://star.pst.qub.ac.uk. Briefly, four grids were calculated corresponding to the Galaxy, the Large Magellanic Cloud (LMC) and SMC and a lower metallicity regime.…”

Section: Discussionmentioning

confidence: 99%

“…The tlusty atmospheric parameters have been determined using an interrelated iterative process (see Thompson et al 2006, 2007). Effective temperatures, T eff , were determined using the silicon ionization balance from the multiplets of Si ii (4128, 4130 Å) and Si iii (4552, 4567, 4574 Å) and the Si iv line at 4116 Å (also the 4088 AA Si iv line for HD 126341).…”

Section: Discussionmentioning

confidence: 99%

Iron abundances from optical Fe iii absorption lines in B-type stellar spectra

Thompson¹,

Keenan²,

Dufton³

et al. 2007

Monthly Notices of the Royal Astronomical Society

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The role of optical Fe III absorption lines in B-type stars as iron abundance diagnostics is considered. To date, ultraviolet Fe lines have been widely used in B-type stars, although line blending can severely hinder their diagnostic power. Using optical spectra, covering a wavelength range ∼3560-9200 Å, a sample of Galactic B-type main-sequence and supergiant stars of spectral types B0.5 to B7 are investigated. A comparison of the observed Fe III spectra of supergiants, and those predicted from the model atmosphere codes TLUSTY [plane-parallel, non-local thermodynamic equilibrium (LTE)], with spectra generated using SYNSPEC (LTE), and CMFGEN (spherical, non-LTE), reveal that non-LTE effects appear small. In addition, a sample of main-sequence and supergiant objects, observed with the Fiber-fed Extended Range Optical Spectrograph (FEROS), reveal LTE abundance estimates consistent with the Galactic environment and previous optical studies. Based on the present study, we list a number of Fe III transitions which we recommend for estimating the iron abundance from early B-type stellar spectra.

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“…Barnard 29 and ROA 5701 have been studied several times, primarily due to their relative brightness, using both optical and ultraviolet (UV) spectra (see e.g. Auer & Norris 1974; Norris 1974; Cacciari et al 1984; de Boer 1985; Adelman et al 1994; Conlon, Dufton & Keenan 1994; Dixon & Hurwitz 1998; Moehler et al 1998; Thompson et al 2006). However, the iron abundances have previously been estimated using only the UV spectra.…”

Section: Introductionmentioning

confidence: 99%

Iron abundances of B-type post-asymptotic giant branch stars in globular clusters: Barnard 29 in M 13 and ROA 5701 in ω Cen*

Thompson

Keenan

Dufton

et al. 2007

Monthly Notices of the Royal Astronomical Society

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High‐resolution optical and ultraviolet (UV) spectra of two B‐type post‐asymptotic giant branch (post‐AGB) stars in globular clusters, Barnard 29 in M 13 and ROA 5701 in ω Cen, have been analysed using model atmosphere techniques. The optical spectra have been obtained with FEROS on the ESO 2.2‐m telescope and the 2d‐Coudé spectrograph on the 2.7‐m McDonald telescope, while the UV observations are from the Goddard high‐resolution spectrograph on the Hubble Space Telescope (HST). Abundances of light elements (C, N, O, Mg, Al and S) plus Fe have been determined from the optical spectra, while the UV data provide additional Fe abundance estimates from Fe iii absorption lines in the 1875–1900 Å wavelength region. A general metal underabundance relative to young B‐type stars is found for both Barnard 29 and ROA 5701. These results are consistent with the metallicities of the respective clusters, as well as with previous studies of the objects. The derived abundance patterns suggest that the stars have not undergone a gas–dust separation, contrary to previous suggestions, although they may have evolved from the AGB before the onset of the third dredge‐up. However, the Fe abundances derived from the HST spectra are lower than those expected from the metallicities of the respective clusters, by 0.5 dex for Barnard 29 and 0.8 dex for ROA 5701. A similar systematic underabundance is also found for other B‐type stars in environments of known metallicity, such as the Magellanic Clouds. These results indicate that the Fe iii UV lines may yield abundance values which are systematically too low by typically 0.6 dex and hence such estimates should be treated with caution.

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A non-LTE abundance analysis of the post-AGB star ROA 5701

Cited by 6 publications

References 43 publications

High-resolution spectroscopy of the high-velocity hot post-AGB star LS III +52°24 (IRAS 22023+5249)

High-resolution spectroscopy of the high-velocity hot post-AGB star LS III +52°24 (IRAS 22023+5249)

Iron abundances from optical Fe iii absorption lines in B-type stellar spectra

Iron abundances of B-type post-asymptotic giant branch stars in globular clusters: Barnard 29 in M 13 and ROA 5701 in ω Cen*

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