Astronomy and Astrophysics, volume 641A, 142-142 (2020/9-1)
Validating post-AGB candidates in the LMC and SMC using SALT spectra.
SZCZERBA R., HAJDUK M., PAVLENKO Y.V., HRIVNAK B.J., KAMINSKY B.M., VOLK K., SIODMIAK N., GEZER I., ZACS L., PYCH W. and SARNA M.
Abstract (from CDS):
We selected a sample of post-AGB candidates in the Magellanic Clouds on the basis of their near- and mid-infrared colour characteristics. Fifteen of the most optically bright post-AGB candidates were observed with the South African Large Telescope in order to determine their stellar parameters and thus to validate or discriminate their nature as post-AGB objects in the Magellanic Clouds. The spectral types of absorption-line objects were estimated according to the MK classification, and effective temperatures were obtained by means of stellar atmosphere modelling. Emission-line objects were classified on the basis of the fluxes of the emission lines and the presence of the continuum. Out of 15 observed objects, only 4 appear to be genuine post-AGB stars (27%). In the SMC, 1 out of 4 is post-AGB, and in the LMC, 3 out 11 are post-AGB objects. Thus, we can conclude that the selected region in the colour-colour diagram, while selecting the genuine post-AGB objects, overlaps severely with other types of objects, in particular young stellar objects and planetary nebulae. Additional classification criteria are required to distinguish between post-AGB stars and other types of objects. In particular, photometry at far-IR wavelengths would greatly assist in distinguishing young stellar objects from evolved ones. On the other hand, we showed that the low-resolution optical spectra appear to be sufficient to determine whether the candidates are post-AGB objects.
© ESO 2020
stars: AGB and post-AGB - stars: abundances - stars: atmospheres - stars: emission-line, Be
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<Available at CDS (J/A+A/641/A142): table1.dat fig2.dat fig3.dat fig4.dat>
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