An Optical Region Elemental Abundance Analysis of the HgMn Type Star HR 7775

Wahlgren, G. M.; Dolk, Linus; Kalus, Gabriele; Johansson, Sveneric; Litzén, Ulf; Leckrone, D. S.

doi:10.1086/309239

Cited by 24 publications

(23 citation statements)

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“…There is, however, no evidence for the presence of spectral lines from the secondary at the level of the noise, typically at the 1% level. In the present work, as in the work by Wahlgren et al (2000) which shared the use of some of the spectra presented in this study, a possible contribution to the spectrum of HR 7775 from the binary component was neglected as synthetic calculations showed that such a contribution would likely be very small, with a total contribution to the spectral continuum at the level of 2% altering abundances of the primary star by up to 0.07 dex. Thus, the introduction of a secondary could introduce larger errors than it would hope to reduce.…”

Section: Hr 7775mentioning

confidence: 97%

“…HR 7775 has previously been analysed by Adelman (1994) and Wahlgren et al (2000) in the optical region, and by Smith & Dworetsky (1993) in the ultraviolet. The atmospheric parameters and elemental abundances for HR 7775 are derived from the previous works.…”

Section: Hr 7775mentioning

confidence: 99%

“…The atmospheric parameters and elemental abundances for HR 7775 are derived from the previous works. The stellar parameters adopted in this work were T eff = 10 750 K, log g = 4.0, v sin i = 2 km s −1 , and turbulent velocity = 0 km s −1 , as used by Wahlgren et al (2000). The factors low-rotational velocity, enhanced line strengths for heavy elements, and its well studied nature made HR 7775, along with 32 Aqr, a prime target for the determination of astrophysical gf values for lines of Pr iii and Nd iii.…”

Section: Hr 7775mentioning

confidence: 99%

“…The astrophysical gf values were determined using the implicit assumption that no ionization anomaly exists for neodymium (and praseodymium) in HR 7775 and for praseodymium in 32 Aqr, even though there is no direct evidence against REE ionization anomalies in these stars. Wahlgren et al (2000) noted that some elements in HR 7775 have slightly different abundances when derived from lines of different ionization stages. These differences are generally small enough (0.1-0.2 dex) that they can be explained by errors in gf values, uncertainties in the line fitting procedure or lineblending.…”

Section: Hr 7775mentioning

confidence: 99%

“…Guthrie (1985) noted the likely presence of Pr iii in the HgMn star HR 7775, but did not find any evidence for Pr iii lines in the other seven HgMn stars observed. Strong Pr iii lines in HR 7775 were confirmed by Wahlgren et al (2000) in the region around 5300Å although an accurate abundance could not be determined due to the lack of oscillator strength data. In recent years it was noted that the third spectrum of praseodymium is very strong in some magnetic Ap stars (Mathys & Cowley 1992), even though the second spectrum is weak or absent.…”

Section: Introductionmentioning

confidence: 99%

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The presence of Nd and Pr in HgMn stars

Dolk

Wahlgren

Lundberg³

et al. 2002

A&A

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Abstract.Optical region spectra for a number of upper main sequence chemically peculiar (CP) stars have been observed to study singly and doubly ionized praseodymium and neodymium lines. In order to improve existing atomic data of these elements, laboratory measurements have been carried out with the Lund VUV Fourier Transform Spectrometer (FTS). From these measurements wavelengths and hyperfine structure (hfs) have been studied for selected Pr ii, Pr iii and Nd iii lines of astrophysical interest. Radiative lifetimes for some excited states of Pr ii have been determined with the aid of laser spectroscopy at the Lund Laser Center (LLC) and have been combined with branching fractions measured in the laboratory to calculate gf values for some of the stronger optical lines of Pr ii. With the aid of the derived gf values and laboratory measurements of the hfs, a praseodymium abundance was derived from selected Pr ii lines in the spectrum of the Am star 32 Aqr. This abundance was used to derive astrophysical gf values for selected Pr iii lines in 32 Aqr, and these gf values were used to get a praseodymium abundance for the HgMn star HR 7775. The praseodymium abundance in HR 7775 was then utilized to derive astrophysical gf values for all observable Pr iii lines in this star. The neodymium abundance, derived from unblended lines of Nd ii in HR 7775, has been utilized to establish astrophysical gf values for observed Nd iii lines in the optical region of this star. Selected Pr iii and Nd iii lines have been identified and studied in a number of HgMn stars and three hot Am stars. The praseodymium and neodymium abundance change rapidly from an approximate 1-1.2 dex enhancement for the hot Am stars to 1.5-3 dex enhancement for the cool HgMn stars, indicating a well-defined boundary between the hot Am and HgMn stars in the vicinity of 10 500 K. The enhancement of praseodymium and neodymium in Am and HgMn stars may be explained by diffusive processes active in the stellar atmosphere, while the observed discontinuity might be explained by a thin hydrogen convection zone thought to be present for the Am stars, but absent in the HgMn stars. The absence of a convection zone would cause the diffused elements to gather higher in the atmosphere of HgMn stars compared to Am stars, and explain the observed increase in abundance.

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Section: Hr 7775mentioning

confidence: 97%

Section: Hr 7775mentioning

confidence: 99%

Section: Hr 7775mentioning

confidence: 99%

Section: Hr 7775mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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