HD 213258: a new rapidly oscillating, super-slowly rotating, strongly magnetic Ap star in a spectroscopic binary

We report about HD 213258, an Ap star that we recently identified as presenting a unique combination of rare, remarkable properties. Our study of this star is based on ESPaDOnS Stokes I and V data obtained at 7 epochs spanning a time interval slightly shorter than 2 years, on TESS data, and on radial velocity measurements from the CORAVEL data base. We confirm that HD 213258 is definitely an Ap star. We found that, in its spectrum, the Fe II {\lambda}6149.2 {\AA} line is resolved into its two magnetically split components. The mean magnetic field modulus of HD 213258, ~ 3.8 kG does not show significant variations over ~2 years. Comparing our mean longitudinal field determinations with a couple of measurements from the literature, we show that the stellar rotation period must likely be of the order of 50 years, with a reversal of the field polarity. Moreover, HD 213258 is a rapidly oscillating Ap (roAp) star, in which high overtone pulsations with a period of 7.58 min are detected. Finally, we confirm that HD 213258 has a mean radial velocity exceeding (in absolute value) that of at least 99% of the Ap stars. The radial velocity shows low amplitude variations, which suggests that the star is a single-line spectroscopic binary. It is also a known astrometric binary. While its orbital elements remain to be determined, its orbital period likely is one of the shortest known for a binary roAp star. Its secondary is close to the borderline between stellar and substellar objects. There is a significant probability that it may be a brown dwarf. While most of the above-mentioned properties, taken in isolation, are observed in a small fraction of the whole population of Ap stars, the probability that a single star possesses all of them is extremely low. This makes HD 213258 an exceptionally interesting object that deserves to be studied in detail in the future.Comment: Accepted for publication in A&A; 6 pages, 4 figure

Project VeSElkA : Preliminary results for CP stars recently observed with ESPaDOnS †

Abstract. We present the first results for the estimation of gravity and effective temperature of poorly studied chemically peculiar stars recently observed with the spectropolarimeter ESPaDOnS at CFHT in the frame of the VeSElkA (Vertical Stratification of Elements Abundance) project. A grid of theoretical stellar atmosphere models with the corresponding fluxes has been calculated using the PHOENIX code. We have used these fluxes to fit Balmer line profiles employing the code FITSB2 that produces estimates of the effective temperature, surface gravity and radial velocity for each star

Revealing the nature of HD157087

The new spectropolarimetric spectra of HD 157087 obtained recently with ESPaDOnS at CFHT are analysed to verify the nature of this object. The abundance analysis also reveals evidence of a significant abundance increase towards the deeper atmospheric layers for several chemical elements. Together with the found enhanced abundance of Ca and Sc this fact contradicts the classification of HD 157087 as a marginal Am star