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J/ApJ/836/15  Spectra of the post-AGB star J005252.87-722842.9  (Kamath+, 2017)

Discovery of a metal-poor, luminous post-AGB star that failed the third dredge-up. Kamath D., Van Winckel H., Wood P.R., Asplund M., Karakas A.I., Lattanzio J.C. <Astrophys. J., 836, 15-15 (2017)> =2017ApJ...836...15K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Spectroscopy ; Abundances ; Equivalent widths Keywords: Magellanic Clouds; methods: observational; stars: abundances; stars: AGB and post-AGB; stars: chemically peculiar; stars: evolution Abstract: Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. In this paper we present the first observational evidence of a star that has failed the third dredge-up (TDU). J005252.87-722842.9 is an A-type (Teff=8250±250K) luminous (8200±700L) metal-poor ([Fe/H]=-1.18±0.10) low-mass (Minitial∼1.5-2.0M) post-AGB star in the Small Magellanic Cloud. Through a systematic abundance study, using high-resolution optical spectra from UVES, we found that this likely post-AGB object shows an intriguing photospheric composition with no confirmed carbon-enhancement (upper limit of [C/Fe]<0.50) nor enrichment of s-process elements. We derived an oxygen abundance of [O/Fe]=0.29±0.1. For Fe and O, we took the effects of nonlocal thermodynamic equilibrium into account. We could not derive an upper limit for the nitrogen abundance as there are no useful nitrogen lines within our spectral coverage. The chemical pattern displayed by this object has not been observed in single or binary post-AGBs. Based on its derived stellar parameters and inferred evolutionary state, single-star nucleosynthesis models predict that this star should have undergone TDU episodes while on the AGB, and it should be carbon enriched. However, our observations are in contrast with these predictions. We identify two possible Galactic analogs that are likely to be post-AGB stars, but the lack of accurate distances (hence luminosities) to these objects does not allow us to confirm their post-AGB status. If they have low luminosities, then they are likely to be dusty post-RGB stars. The discovery of J005252.87-722842.9 reveals a new stellar evolutionary channel whereby a star evolves without any TDU episodes. Description: We obtained high-resolution optical spectra using the UVES echelle spectrograph, mounted on the 8m UT2 Kueyen Telescope of the VLT array at the Paranal Observatory of ESO in Chile. Objects: ------------------------------------------------------------------------------ RA (ICRS) DE Designation(s) ------------------------------------------------------------------------------ 00 52 52.87 -72 28 42.9 J005252.87-722842.9 = SSTISAGEMC J005252.92-722843.1 ------------------------------------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 40 131 The linelist of J005252.87-722842.9 fig2/* 0 3 The 3 FITS spectra showed in Figure 2
Description of file: Three FITS files, J005252BLUEfinal.fits, J005252REDLfinal.fits, and J005252REDUfinal.fits of high-resolution optical spectra using the UVES echelle spectrograph mounted on the 8m UT2 Kueyen Telescope of the VLT array at the Paranal Observatory of ESO in Chile. We used the dichroic beam-splitter which resulted in a wavelength coverage in the blue arm from approximately 3280 to 4530 Angstroms and in the red arm for the lower and upper part of the mosaic CCD chip from approximately 4780 to 5770 Angstroms and from 5800 to 6810 Angstroms, respectively. See also: J/ApJS/92/125 : Post-AGB evolution (Vassiliadis+, 1994) J/A+A/425/595 : OGLE+2MASS+DENIS LPV in Magellanic Clouds (Groenewegen, 2004) J/ApJS/155/651 : Evolution of extremely metal-poor stars (Herwig+, 2004) J/AJ/132/2268 : SAGE calibration stars (Meixner+, 2006) J/ApJ/655/212 : S3MC IRAC and MIPS photometry (Bolatto+, 2007) J/A+A/484/815 : Scaled solar tracks and isochrones (Bertelli+, 2008) J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010) J/A+A/533/A109 : Pisa pre-main sequence tracks and isochrones (Tognelli+, 2011) J/A+A/530/A90 : Optically bright post-AGB population of LMC (van Aarle+, 2011) J/A+A/557/A104 : CO observations of post-AGB stars (Bujarrabal+, 2013) J/A+A/554/A106 : Abundance study of LMC post-AGB stars (van Aarle+, 2013) J/A+A/560/A44 : Abundances of LMC bar and disk stars (Van der Swaelmen+, 2013) J/MNRAS/439/2211 : Post-AGB/RGB and YSOs in SMC (Kamath+, 2014) J/A+A/568/A25 : C and O abundances in stellar populations (Nissen+, 2014) J/A+A/583/A56 : Abundance study of two LMC post-AGB stars (De Smedt+, 2015) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 4 F4.1 --- Ion [8/28.1] Atomic number+0.1*ionisation stage 6- 13 F8.3 0.1nm lambda [3408.7/6456.4] Wavelength in rest frame; in Angstroms 15- 20 F6.3 eV chi [0/10.8] Excitation potential 22- 27 F6.3 [-] loggf [-4.1/0.4] Log Oscillator strength 29- 34 F6.2 10-13m EW [3.8/124] Equivalenth width; in milli-Angstroms 36- 40 F5.3 [-] Abd [2.1/8.3] Obtained abundance
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Sep-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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