Surface magnetic field of the A-type metallic-line star omicron Pegasi revisited

TL;DR

This study revisits the magnetic field measurement of the star o Peg using high-quality spectra and rigorous simulations, confirming a mean magnetic field of approximately 1-2kG, consistent with earlier findings but with improved methodology.

Contribution

It provides a more accurate and physically rigorous re-evaluation of o Peg's magnetic field, improving upon previous empirical estimates with high-quality data and detailed modeling.

Findings

Confirmed the presence of a magnetic field of 1-2kG in o Peg.

Used high-quality spectra and detailed simulations for analysis.

Results are consistent with earlier studies but with improved accuracy.

Abstract

The bright A-type metallic-line star o Peg was reported in the early 1990s to have a surface magnetic field of ~2kG by analyzing the widths and strengths of spectral lines. In respect that those old studies were of rather empirical or approximate nature and the quality of observational data was not sufficient, this problem has been newly reinvestigated based on physically more rigorous simulations of line flux profiles, along with the observed equivalent widths (W) and full-widths at half-maximum (h) of 198 Fe I and 182 Fe II lines measured from the high-quality spectra. Given the Fe abundance derived from the conventional analysis, theoretical W and h values calculated for various sets of parameters were compared with the observed ones, which lead to the following conclusion regarding <H> (mean field strength). (1) An analysis of W yielded <H>~1-1.5kG from Fe II lines with the microturbulence of vt~1.5km/s. (2) A comparison of h resulted in <H>~1.5-2kG as well as the projected rotational velocity of vsini~5km/s. (3) Accordingly, the existence of mean magnetic field on the order of <H>~1-2kG in o Peg was confirmed, which is almost consistent with the consequence of the previous work.