Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005arep...49..714r&link_type=abstract
Astronomy Reports, vol. 49, Issue 9, p.714-723
Astronomy and Astrophysics
Astronomy
Scientific paper
An analysis of high-resolution CCD spectra of the giant 25 Mon, which shows signs of metallicity, and the normal giant HR 7389 is presented. The derived effective temperatures, gravitational accelerations, and microturbulence velocities are T eff = 6700 K, log g = 3.24, and ξ t = 3.1 km/s for 25 Mon and T eff = 6630 K, log g = 3.71, and ξ t = 2.6 km/s for HR 7389. The abundances (log ɛ) of nine elements are determined: carbon, nitrogen, oxygen, sodium, silicon, calcium, iron, nickel, and barium. The derived excess carbon abundances are 0.23 dex for 25 Mon and 0.16 dex for HR 7389. 25 Mon displays a modest (0.08 dex) oxygen excess, with the oxygen excess for HR 7389 being somewhat higher (0.15 dex). The nitrogen abundance is probably no lower than the solar value for both stars. The abundances of iron, sodium, calcium (for HR 7389), barium, and nickel exceed the solar values by 0.22 0.40 dex for both stars. The highest excess (0.62 dex) is exhibited by the calcium abundance for 25 Mon. Silicon displays a nearly solar abundance in both stars—small deficits of -0.03 dex and -0.07 dex for 25 Mon and HR 7389, respectively. No fundamental differences in the elemental abundances were found in the atmospheres of 25 Mon and HR 7389. Based on their T eff and log g values, as well as theoretical calculations, A. Claret estimated the masses, radii, luminosities, and ages of 25 Mon (M/M &sun; = 2.45, log(R/R &sun;) = 0.79, log(L/L &sun;) = 1.85, t = 5.3 × 108 yr) and HR 7389 (M/M &sun; = 2.36, log(R/R &sun;) = 0.50, log(L/L &sun;) = 1.24, t = 4.6 × 108 yr), and also of the stars 20 Peg (M/M &sun; = 2.36, log(R/R &sun;) = 0.73, log(L/L &sun;) = 1.79, t = 4.9 × 108 yr) and 30 LMi (M/M &sun; = 2.47, log(R/R &sun;) = 0.73, log(L/L &sun;) = 1.88, t = 4.8 × 108 yr) studied by the author earlier.
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