Does the A-type Metallic-line Star IW Persei Have Non-Uniform Chemical Anomaly on the Surface?

TL;DR

This study re-examines the surface chemical uniformity of the Am star IW Persei using high-resolution spectra, finding no evidence of phase-dependent chemical anomalies, and confirms its classification as an Am star despite its rapid rotation.

Contribution

The paper provides a new spectroscopic analysis that challenges previous claims of surface chemical patchiness on IW Persei, confirming its Am star status.

Findings

No phase-dependent line-strength variations detected.

IW Persei's chemical abundances support its classification as an Am star.

Surface inhomogeneity is unlikely based on current observations.

Abstract

IW Per, a single-lined spectroscopic binary with a short period of 0.92d, is known to be a A-type metallic-line (Am) star showing anomalous line strengths of specific elements. Previously, Kim (1980) reported that its equivalent widths of CaII 3934, SrII 4215, and ScII 4320 lines (important key lines characterizing the Am anomaly) show cyclic variations in accordance with the rotation phase, implyig that the chemical peculiarities on the surface are not uniform but of rather patchy distribution, though no trial of reconfirmation seems to have been done so far. In order to check the validity of this finding, 10 high-dispesion spectra of IW Per covering different phases were analyzed for these lines by using the spectrum-fitting technique to determine the abundances of Ca, Sr, and Sc and the corresponding equivalent widths. It turned out, however, that no firm evidence of such phase-dependent line-strength variations could be found, suggesting that significant chemical inhomogeneity on the surface of IW Per is unlikely to exist, at least as regards to the period of our observations (2010 December). Meanwhile, the abundances of O, Si, Ca, Ba, and Fe resulting from the 6130-6180A region corroborate that IW Per is a distinct Am star despite that its rotational velocity (~100 km/s) is near to the existent limit of Am phenomenon.