A detailed abundance analysis of the hot post-AGB star ZNG-1 in M10

Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Dufton, P. L.; Pollacco, D.; Magee, H.

doi:10.1046/j.1365-8711.2001.04668.x

Cited by 12 publications

(15 citation statements)

References 22 publications

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“…Some of these sources are high Galactic latitude, hot B-type post-AGB stars (e.g. Conlon et al 1993;Mooney et al 2001) that show strong carbon deficiencies. In the more extreme cases they will probably never become PNe.…”

Section: Evolutionary Connectionsmentioning

confidence: 99%

Lithium and zirconium abundances in massive Galactic O-rich AGB stars

García–Hernández¹,

García-Lario²,

Plez³

et al. 2006

A&A

121

135

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Lithium and zirconium abundances (the latter taken as representative of s-process enrichment) are determined for a large sample of massive Galactic O-rich AGB stars, for which high-resolution optical spectroscopy has been obtained (R ∼ 40 000−50 000). This was done by computing synthetic spectra based on classical hydrostatic model atmospheres for cool stars and using extensive line lists. The results are discussed in the framework of "hot bottom burning" (HBB) and nucleosynthesis models. The complete sample is studied for various observational properties such as the position of the stars in the IRAS two-colour diagram ([12] − [25] vs.[25] − [60]), Galactic distribution, expansion velocity (derived from the OH maser emission), and period of variability (when available). We conclude that a considerable fraction of these sources are actually massive AGB stars (M > 3−4 M ) experiencing HBB, as deduced from the strong Li overabundances we found. A comparison of our results with similar studies carried out in the past for the Magellanic Clouds (MCs) reveals that, in contrast to MC AGB stars, our Galactic sample does not show any indication of s-process element enrichment. The differences observed are explained as a consequence of metallicity effects. Finally, we discuss the results obtained in the framework of stellar evolution by comparing our results with the data available in the literature for Galactic post-AGB stars and PNe.

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Section: Evolutionary Connectionsmentioning

confidence: 99%

Lithium and zirconium abundances in massive Galactic O-rich AGB stars

García–Hernández¹,

García-Lario²,

Plez³

et al. 2006

A&A

121

135

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“…NGC 6712 ZNG-1 was analysed with respect to HR 6825 and β Ori; both observed with UCLES instrument at the Anglo-Australian Telescope and reduced using standard methods (see, for example Mooney et al 2001). …”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…Observed features in the spectra of M 10 ZNG-1, M 15 ZNG-1 and NGC 6712 ZNG-1 have been compared with model atmospheres generated using  (see Hubeny 1988;Hubeny & Lanz 1992 and LTE radiative transfer codes (see, for example, Mooney et al 2001). Keenan & Lennon 1984;Gies & Lambert 1992).…”

Section: Stellar Atmospheric Parametersmentioning

confidence: 99%

“…However, many globular cluster post-AGB stars display near solar helium abundances, viz. M 10 ZNG-1 (Mooney et al 2001), Barnard 29 (Conlon et al 1994;Moehler et al 1998b) and ROB 162 in NGC 6397 (Heber & Kudritzki 1986). As a result, the effective temperature was estimated from the requirement that the helium abundance was solar.…”

Section: Ngc 6712 Zng-1: T Eff Log G and ξmentioning

confidence: 99%

“…As a result of a continuing programme to investigate B-type stars in the halo of our Galaxy (Keenan 1992), we have identified several hot post-AGB stars on the basis of their derived atmospheric parameters and chemical compositions (Conlon et al 1991(Conlon et al , 1993(Conlon et al , 1994McCausland et al 1992;Mooney et al 2001). Although these hotter stars should be evolving from their cooler counterparts, the abundance patterns of the former appear to display significant differences to those of the latter, most notably for carbon, with significant underabundances having been observed in several hot post-AGB stars (see, for example, Conlon et al 1991Conlon et al , 1994Mooney et al 2001). Indeed, the observed CNO abundance pattern in the hot post-AGBs appears to be incompatible with the products of helium burning which should be mixed to the stellar surface via the third dredge-up on the AGB.…”

Section: Introductionmentioning

confidence: 99%

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High-resolution spectroscopy of globular cluster post-Asymptotic Giant Branch stars

Mooney

Rolleston

Keenan

et al. 2004

A&A

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Abstract. We present model atmosphere analyses of high resolution Keck and VLT optical spectra for three evolved stars in globular clusters, viz. ZNG-1 in M 10, ZNG-1 in M 15 and ZNG-1 in NGC 6712. The derived atmospheric parameters and chemical compositions confirm the programme stars to be in the post-Asymptotic Giant Branch (post-AGB) evolutionary phase. Differential abundance analyses reveal CNO abundance patterns in M 10 ZNG-1, and possibly M 15 ZNG-1, which suggest that both objects may have evolved off the AGB before the third dredge-up occurred. The abundance pattern of these stars is similar to the third class of optically, bright post-AGB objects discussed by van Winckel (1997). Furthermore, M 10 ZNG-1 exhibits a large C underabundance (with [C/O] ∼ −1.6 dex), typical of other hot post-AGB objects. Differential [α/Fe] abundance ratios in both M 10 ZNG-1 and NGC 6712 ZNG-1 are found to be approximately 0.0 dex, with the Fe abundance of the former being in disagreement with the cluster metallicity of M 10. Given that the Fe absorption features in both M 10 ZNG-1 and NGC 6712 ZNG-1 are well observed and reliably modelled, we believe that these differential Fe abundance estimates to be secure. However, our Fe abundance is difficult to explain in terms of previous evolutionary processes that occur on both the Horizontal Branch and the AGB.

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Ca II K interstellar observations towards early-type disc and halo stars

Smoker

Rolleston

Kay

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We present high‐resolution (R=λ/Δλ∼ 40 000) Ca ii K interstellar observations (λair= 3933.66 Å) towards 88 mainly B‐type stars, of which 74 are taken from the Edinburgh–Cape or Palomar–Green surveys, and 81 have |b| > 25°. The majority of the data come from previously existing spectroscopy, although also included are 18 new observations of stars with echelle spectra taken with UVES on the Very Large Telescope UT2 (Kueyen). Some 49 of the sample stars have distance estimates above the Galactic plane (|z|) ≥ 1 kpc, and are thus good probes of the halo interstellar medium. Of the 362 interstellar Ca K components that we detect, 75 (21 per cent) have absolute values of their LSR velocity values exceeding 40 km s−1. In terms of the deviation velocity for the sightlines with distance estimates, 46/273 (17 per cent) of components have velocity values exceeding those predicted by standard Galactic rotation by more than 40 km s−1. Combining this data set with previous observations, we find that the median value of the reduced equivalent width (REW) of stars with |z| ≥ 1 kpc (EW×sin |b|) is ∼115 m Å (n= 80), similar to that observed in extragalactic sightlines by Bowen. Using data of all z distances, the REW at infinity is found to be ∼130 m Å, with the scaleheight (l) of the Ca ii K column density distribution being ≈800 pc (n= 196) and reduced column density at infinity of log[N(Ca ii K) cm−2]∼12.24. This implies that ∼30 per cent of Ca ii K absorption occurs at distances exceeding ∼1 kpc. For nine sightlines with distance exceeding 1 kpc and with a companion object within 5°, we find that all but two have values of Ca ii reduced equivalent width the same to within ∼20 per cent, when the REW of the nearest object is extrapolated to the distance of the further of the pair, and assuming l= 800 pc. For 29 of our sightlines with |z| ≥ 1 kpc and a H i detection from the Leiden–Dwingeloo survey (beamsize of 0.5°), we find log(N(Ca ii K)/N(H i)) ranging from −7.4 to −8.4. Values of the Ca ii K abundance relative to neutral hydrogen (log[N(Ca ii K) cm−2] – log[N(H i) cm−2]) are found to be more than ∼0.5 dex higher in stars with distances exceeding ≈100 pc, when compared with the (log[N(Ca ii K) cm−2]– log[N(Htot) cm−2]) values found in nearby sightlines such as those in Wakker & Mathis (2000). Finally, stellar Ca ii K equivalent widths of the sample are determined for 26 objects.

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A detailed abundance analysis of the hot post-AGB star ZNG-1 in M10

Cited by 12 publications

References 22 publications

Lithium and zirconium abundances in massive Galactic O-rich AGB stars

Lithium and zirconium abundances in massive Galactic O-rich AGB stars

High-resolution spectroscopy of globular cluster post-Asymptotic Giant Branch stars

Ca II K interstellar observations towards early-type disc and halo stars

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