C.D.S. - SIMBAD4 rel 1.7 - 2020.10.25CET10:16:02

2015A&A...574A..29W - Astronomy and Astrophysics, volume 574A, 29-29 (2015/2-1)

The prospective search for highly ionized technetium in hot (pre-) white dwarfs.


Abstract (from CDS):

The discovery of technetium (Tc) in the atmospheres of red giants by Merrill (1952ApJ...116...21M) constituted convincing proof that s-process nucleosynthesis is indeed occurring in evolved stars. In principle, Tc should still be present in the atmospheres of hot post-AGB stars and (pre-) white dwarfs although, due to radioactive decay, it should be present in decreasing quantities along post-AGB evolution. The recent discovery of a large number of trans-iron group elements in hot white dwarfs with atomic numbers in the range A=30-56 (Zn to Ba) raises the prospect that Tc (A=43) may also be detected. However, this is currently not feasible because no atomic data exist for ionization stages beyond TcII. As an initial step, we calculated atomic energy levels and oscillator strengths of TcIV-VI and used these data to compute non-local thermodynamic equilibrium (NLTE) model atmospheres to estimate at which minimum abundance level Tc could be detected. We show that Tc lines can be found in ultraviolet spectra of hot white dwarfs provided Tc is as abundant as other detected trans-Fe elements. We find that radiative levitation can keep Tc in large, easily detectable quantities in the atmosphere. A direct identification of Tc lines is still not feasible because wavelength positions cannot be computed with necessary precision. Laboratory measurements are necessary to overcome this problem. Our results suggest that such efforts are beneficial to the astrophysical community.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: evolution - stars: AGB and post-AGB - white dwarfs - atomic data - line: identification

VizieR on-line data: <Available at CDS (J/A+A/574/A29): table1.dat table2.dat table3.dat table4.dat table5.dat table6.dat>

Simbad objects: 2

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Number of rows : 2

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 RX J0503.9-2854 WD* 05 03 55.5147387403 -28 54 34.631014015 12.29 13.55 13.58     DO 91 0
2 BD+52 913 WD* 05 05 30.6182785658 +52 49 51.920797126 10.25 11.44 11.69 11.93 12.108 DA.8 992 0

    Equat.    Gal    SGal    Ecl

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