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

Takeda Y.

Acta Astronomica

2023

Vol. 73, No. 1

35--55

IW Per, a single-lined spectroscopic binary with a short period of 0.92 d, is known to be a A-type metallic-line (Am) star showing anomalous line strengths of specific elements. It was previously 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, implying that the chemical peculiarities on the surface are not uniform but of rather patchy distribution. However, no attempts of reconfirmation have been done so far. In order to check the validity of this finding, ten high-dispersion 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 during the period of our observations (2010 December). Meanwhile, the abundances of O, Si, Ca, Ba, and Fe resulting from the 6130-6180 Å region corroborate that IW Per is a distinct Am star (though the degree of peculiarity differs from element to element) despite that its rotational velocity (≈100 km/s) is near to the limit of Am phenomenon.

Variability of the Ap Star HD 9996

Bychkov V. D., Bychkova L. V., Madej J., Shatilov A. V.

Acta Astronomica

2012

Vol. 62, No. 3

297--311

We present here new measurements of the longitudinal magnetic field (Be) in the binary system HD 9996, where the primary companion is an Ap star. Series of 63 Be observations was obtained in years 1994-2011 with the 1-m optical telescope of the Special Astrophysical Observatory (Russia). New magnetic data allowed us to refine the long-term magnetic period of HD 9996 to Pmag=21.8 years. Compilation of archival photometric data showed the existence of long-term variations of HD 9996 in time scale of 22-23 yr consistent with Pmag. We identify Pmag with the precession period of the primary Ap star and summarize search for a short-term rotational period and the rotational line broadening in this star.

Investigation of the Rapid Magnetic Field Variability in γ Equulei

Bychkov V. D., Bychkova L. V., Madej J.

Acta Astronomica

2005

Vol. 55, No. 1

141--149

We investigated magnetic variability of the roAp star &gamma Equ (HD 201601) with high time resolution. Measurements of the stellar longitudinal magnetic field Be were performed with the hydrogen line polarimeter and the 6-m optical telescope of the Special Astrophysical Observatory (Russia) on 20/21 August 1989. We obtained a single 3-hour series of 1720 rapid Be measurements for this star with the average time resolution of 6.6 sec. The averaged value of Be on this night equals to -750±22 G. Both the power spectrum and the amplitude spectrum of the Be time series are essentially flat. However, they show the presence of a marginally significant magnetic period at PB=3.596 min which is real with the probability of 67%. The amplitude of the magnetic field variations with this period equals 347±31 G. We did not detect variations of Be field in γ Equ with the well-known photometric period, Pphot=12.44 min.