The discovery of two new rapidly oscillating Ap stars, HD92499 and HD143487

Abstract

We report the discovery of short periodic radial velocity variations in the stars HD 92499 and HD 143487. Both stars show strong magnetic fields and large overabundances of rare earth elements and belong to the class of cool chemically peculiar stars of the main sequence. They are therefore new rapidly oscillating Ap stars. Pulsations were detected from analysis of high time resolution spectra obtained with the European Southern Observatory Very Large Telescope by using a cross-correlation method for large spectral bands and from combinations of lines belonging to rare earth elements. The amplitudes of the pulsations are small and do not exceed several dozens of m s −1 with periods of around 10 min. The detection of such low amplitudes is important for the determination of which magnetic Ap stars pulsate, and which are constant, a distinction important for the understanding of the pulsation driving mechanism in these stars.

TESS cycle 1 observations of roAp stars with 2-min cadence data

“…The star is classified as A3 SrEuCr in Renson & Manfroid (2009). It was identified as an roAp star by Elkin et al (2010), following the analysis of high time resolution spectra obtained with UVES from which a low amplitude pulsation with a period around 10 min was inferred. The roAp nature of this star was later confirmed by Kochukhov et al (2013) based on the analysis of a larger set of UVES spectra which allowed the detection of the pulsations in the lines of rare-earth elements as well as in the core of H α and the determination of a pulsation period of 9.63 min (1.730 mHz; 149.47 d −1 ) with amplitudes up to 110 m s −1 .…”

“…TIC 146715928 (HD 92499) was classified as A2p SrEuCr (Houk 1978) with T eff values ranging from 7200 K to 7810 K (Hubrig & Nesvacil 2007;Freyhammer et al 2008b;Elkin et al 2010), and log g = 4.1 ± 0.2 (cm s −2 ). Elkin et al (2010) also provided a full chemical abundance analysis of this star.…”

“…TIC 146715928 (HD 92499) was classified as A2p SrEuCr (Houk 1978) with T eff values ranging from 7200 K to 7810 K (Hubrig & Nesvacil 2007;Freyhammer et al 2008b;Elkin et al 2010), and log g = 4.1 ± 0.2 (cm s −2 ). Elkin et al (2010) also provided a full chemical abundance analysis of this star. A mean magnetic field modulus of 8.5 kG was derived from FEROS spectra by Hubrig & Nesvacil (2007) which was corroborated by Mathys (2017) who also suggested the rotation period of TIC 146715928 must be greater than 5 yr. TIC 146715928 has a v sin i ≈ 3.5 km s −1 (Hubrig & Nesvacil 2007;Elkin et al 2010).…”

KIC 7582608: a new Kepler roAp star with frequency variability

“…However, there are now some stars that have been detected through spectral line variations alone (e.g. Elkin et al 2010Elkin et al , 2011Kochukhov et al 2013) and, with the launch of the Kepler satellite, high-precision spacebased photometry (e.g. Balona et al 2011b,a;Kurtz et al 2011;Niemczura et al 2014).…”

HD 24355 observed by theKepler K2mission: a rapidly oscillating Ap star pulsating in a distorted quadrupole mode

“…Martinez, Kurtz & Kauffmann 1991;Martinez & Kurtz 1994), with later studies using high-resolution spectroscopy to detect line profile variations in Ap stars caused by pulsational velocity shifts (e.g. Savanov, Malanushenko & Ryabchikova 1999;Kochukhov & Ryabchikova 2001;Hatzes & Mkrtichian 2004;Mkrtichian et al 2008;Elkin et al 2010;Elkin, Kurtz & Mathys 2011;Kochukhov et al 2013). Most recently, the use of the Super-WASP (Wide Angle Search for Planets) ground-based photometric survey led to the identification of 11 roAp stars (Holdsworth et al 2014a;Holdsworth 2015).…”