The nature of the late B-type stars HD 67044 and HD 42035

Abstract

While monitoring a sample of apparently slowly rotating superficially normal bright late B and early A stars in the northern hemisphere, we have discovered that HD 67044 and HD 42035, hitherto classified as normal late B-type stars, are actually respectively a new chemically peculiar star and a new spectroscopic binary containing a very slow rotator HD 42035 S with ultra-sharp lines (vsini = 3.7 km/s) and a fast rotator HD 42035 B with broad lines. The lines of Ti, Cr, Mn, Sr, Y, Zr and Ba are conspicuous features in the high resolution SOPHIE spectrum of HD 67044. The HgII line at 3983.93 A is also present as a weak feature. The composite spectrum of HD 42035 is characterised by very sharp lines formed in HD 42035 S superimposed onto the shallow and broad lines of HD 42035 B. These very sharp lines are mostly due to light elements from C to Ni, the only heavy species definitely present are Sr and Ba. Selected lines of 21 chemical elements from He up to Hg have been synthesized using model atmospheres computed with ATLAS9 and the spectrum synthesis code SYNSPEC48 including hyperfine structure of various isotopes when relevant. Abundances of these key elements have been derived HD 67044 and HD 42035 S. HD 67044 is found to have distinct enhancements of Ti, Cr, Mn, Sr, Y, Zr, Ba and Hg and underabundances in He, C, O, Ca and Sc which shows that this star is not a superficially normal late B-type star, but actually is a new CP star most likely of the HgMn type. HD 42035 S has provisional underabundances of the light elements from C to Ti and overabundances of heavier elements up to barium. More accurate fundamental parameters and abundances for HD 42035 S and HD 42035 B will be derived if we manage to disentangle their spectra. They will help clarify the status of the two components in this interesting new spectroscopic binary.Comment: 30 pages, 4 figures, 2 tables, accepted in APSS. arXiv admin note: text overlap with arXiv:1504.0272

First results from the LIFE project: discovery of two magnetic hot evolved stars

“…4), it can be seen that the binary consists of a very slowly rotating component and a very rapidly rotating component. This is consistent with the findings of Monier et al (2016), who report numerous peculiarities of the chemical abundances, which we also observe in our spectra. We find a T eff of 10500 K which is consistent with the values given in Monier et al (2016).…”

“…This is consistent with the findings of Monier et al (2016), who report numerous peculiarities of the chemical abundances, which we also observe in our spectra. We find a T eff of 10500 K which is consistent with the values given in Monier et al (2016). However, as stated by Monier et al (2016), this value has significant flux contributions from both stars, and so the evolutionary status of both stars remains unclear.…”

“…We find a T eff of 10500 K which is consistent with the values given in Monier et al (2016). However, as stated by Monier et al (2016), this value has significant flux contributions from both stars, and so the evolutionary status of both stars remains unclear. For this reason HD 42035 is not shown in Fig.…”

HR 8844: A New Transition Object between the Am Stars and the HgMn Stars?

“…We have already reported on the discovery of 4 new HgMn stars (Monier et al 2015) whose spectra display strong Hg II lines at 3984 Å and strong Mn II lines. In the process of our analysis of the B8-B9V sample, we also found that HD 67044 is most likely another new HgMn star (Monier et al 2016). Royer et al (2014) performed abundance analyses for C, O, Mg, Si, Ca, Sc, Ti, Cr, Fe, Sr, Y, Zr using Takeda's automated procedure and classified HR 8844 as "probably normal": the four criteria used for the automatic classification were not fully consistent, depending on the chemical species used.…”

Elemental abundances of HD 87240, member of the young open cluster NGC 3114

“…The derived abundance pattern of HD 87240 departs strongly from the solar composition which definitely shows that HD 87240 is not a superficially normal late B star but is definitely a new CP star. We have already reported on the discovery of 6 new CP stars of the HgMn type among late B-type stars in Monier et al (2015), Monier et al (2016) and Monier et al (2018). HD 87240 has overabundances of both the rare earths and of Pt and Hg and its effective temperature and surface gravity place it among the Bp Si and the HgMn stars.…”