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DC Field | Value | Language |
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dc.contributor.author | Sumangala Rao, S | - |
dc.contributor.author | Pandey, G | - |
dc.contributor.author | Lambert, D. L | - |
dc.contributor.author | Giridhar, S | - |
dc.date.accessioned | 2011-08-11T14:11:40Z | - |
dc.date.available | 2011-08-11T14:11:40Z | - |
dc.date.issued | 2011-08-10 | - |
dc.identifier.citation | The Astrophysical Journal, Vol. 737, No. 1, L7 | en |
dc.identifier.uri | http://hdl.handle.net/2248/5547 | - |
dc.description | Open Access | en |
dc.description.abstract | We have conducted an LTE abundance analysis for SAO 40039, a warm post-AGB star whose spectrum is known to show surprisingly strong He I lines for its effective temperature and has been suspected of being H-deficient and He-rich. High-resolution optical spectra are analyzed using a family of model atmospheres with different He/H ratios. Atmospheric parameters are estimated from the ionization equilibrium set by neutral and singly ionized species of Fe and Mg, the excitation of Fe I and Fe II lines, and the wings of the Paschen lines. On the assumption that the He I lines are of photospheric and not chromospheric origin, a He/H ratio of approximately unity is found by imposing the condition that the adopted He/H ratio of the model atmosphere must equal the ratio derived from the observed He I triplet lines at 5876, 4471, and 4713 Å, and singlet lines at 4922 and 5015 Å. Using the model with the best-fitting atmospheric parameters for this He/H ratio, SAO 40039 is confirmed to exhibit mild dust-gas depletion, i.e., the star has an atmosphere deficient in elements of high condensation temperature. The star appears to be moderately metal-deficient with [Fe/H] = –0.4 dex. But the star's intrinsic metallicity as estimated from Na, S, and Zn, elements of a low condensation temperature, is [Fe/H]o sime –0.2 ([Fe/H]o refers to the star's intrinsic metallicity). The star is enriched in N and perhaps O as well, changes reflecting the star's AGB past and the event that led to He enrichment. | en |
dc.language.iso | en | en |
dc.publisher | IOP Publishing | en |
dc.relation.uri | http://dx.doi.org/10.1088/2041-8205/737/1/L7 | en |
dc.rights | © IOP Publishing | en |
dc.subject | Stars: abundances | en |
dc.subject | Stars: atmospheres | en |
dc.subject | Stars: evolution | en |
dc.subject | Stars: fundamental parameters | en |
dc.title | Is the Post-AGB Star SAO 40039 Mildly Hydrogen-Deficient? | en |
dc.type | Article | en |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
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Is the Post-AGB Star SAO 40039 Mildly Hydrogen-Deficient.pdf | Open Access | 279.54 kB | Adobe PDF | View/Open |
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