Mercury in the HgMn Stars X Lupi and HR 7775

Published

October 12, 2021

Author(s)

C R. Proffitt, T Brage, D S. Leckrone, G Wahlgren, J C. Brandt, Craig J. Sansonetti, Joseph Reader, S Johansson

Abstract

Observations of mercury lines in the HgMn stars chi Lupi and HR 7775 made with the Hubble Space Telescope's Goddard High Resolution Spectrograph are presented and analyzed. In chi Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure 204Hg), but strong ionizaiton anomalies are present, with UV Hg I lines being too weak, and Hg III lines too strong for the abundance derived from lines of Hg II, which is the majority ionization state. Observations of mercury in HR 7775 show less extreme isotope and ionizaiton anomalies. We find that the ionization anomaly in the Hg I resonance lines can be plausibly explained as a non-LTE effect, but the same non-LTE calculations show that the Hg III ionizaiton anomaly in chi Lupi cannot be explained in this way. Radiative force calculations show that the observed mercury abundance cannot be supported in the atmosphere by the radiative forces alone. We suggest that weak mixing brings mercury into the line forming region from below the photosphere, while a wind of the order of 10- 14 M(solar) yr-1 supports a cloud of g III at very small optical depths.

Citation

The Astrophysical Journal

Pub Type

Journals

Keywords

diffusion, elemental abundances, isotopes, mercury, spectrum, star, transition probabilities

Citation

Proffitt, C. , Brage, T. , Leckrone, D. , Wahlgren, G. , Brandt, J. , Sansonetti, C. , Reader, J. and Johansson, S. (2021), Mercury in the HgMn Stars X Lupi and HR 7775, The Astrophysical Journal (Accessed October 9, 2025)