We have estimated elemental abundances of the planetary nebula Hen2-436 in the Sagittarius ( Sgr ) spheroidal dwarf galaxy using ESO/VLT FORS2 , Magellan/MMIRS , and Spitzer /IRS spectra .
We have detected candidates of fluorine [ F ii ] \lambda 4790 , krypton [ Kr iii ] \lambda 6826 , and phosphorus [ P ii ] \lambda 7875 lines and successfully estimated the abundances of these elements ( [ F/H ] =+1.23 , [ Kr/H ] =+0.26 , [ P/H ] =+0.26 ) for the first time .
These elements are known to be synthesized by neutron capture process in the He-rich intershell during the thermally pulsing AGB phase .
We present a relation between C , F , P , and Kr abundances among PNe and C-rich stars .
The detections of F and Kr in Hen2-436 support the idea that F and Kr together with C are synthesized in the same layer and brought to the surface by the third dredge-up .
We have detected N ii and O ii optical recombination lines ( ORLs ) and derived the N ^ { 2 + } and O ^ { 2 + } abundances .
The discrepancy between the abundance derived from the oxygen ORL and that derived from the collisionally excited line is > 1 dex .
To investigate the status of the central star of the PN , nebula condition , and dust properties , we construct a theoretical spectral energy distribution ( SED ) model to match the observed SED with Cloudy .
By comparing the derived luminosity and temperature of the central star with theoretical evolutionary tracks , we conclude that the initial mass of the progenitor is likely to be \sim 1.5-2.0 M _ { \odot } and the age is \sim 3000 yr after the AGB phase .
The observed elemental abundances of Hen2-436 can be explained by a theoretical nucleosynthesis model with a star of initial mass 2.25 M _ { \odot } , Z =0.008 and LMC compositions .
We have estimated the dust mass to be 2.9 \times 10 ^ { -4 } M _ { \odot } ( amorphous carbon only ) or 4.0 \times 10 ^ { -4 } M _ { \odot } ( amorphous carbon and PAH ) .
Based on the assumption that most of the observed dust is formed during the last two thermal pulses and the dust-to-gas mass ratio is 5.58 \times 10 ^ { -3 } , the dust mass-loss rate and the total mass-loss rate are < 3.1 \times 10 ^ { -8 } M _ { \odot } yr ^ { -1 } and < 5.5 \times 10 ^ { -6 } M _ { \odot } yr ^ { -1 } , respectively .
Our estimated dust mass-loss rate is comparable to a Sgr dwarf galaxy AGB star with similar metallicity and luminosity .