Non-local thermodynamic equilibrium spectral analysis of five hot, hydrogen-deficient pre-white dwarfs

Werner, K.; Reindl, N.; Dorsch, M.; Geier, S.; Munari, U.; Raddi, R.

doi:10.1051/0004-6361/202142397

Cited by 8 publications

(5 citation statements)

References 59 publications

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“…The effective temperature of JL 9 was increased from 68,820 K obtained from the optical fit alone to 75,000 K, as shown in Table 2, in order to reproduce the ionization balance of the Fe VI and Fe VII ions that are observed in the FUSE and STIS spectra. Werner et al (2022) came to a similar conclusion although their temperature and gravity are somewhat different with T eff = 80,000 ± 5000 K and g log 5.2 0.3, =   but the error analysis described in Section 5.1 shows that this has a negligible effect on the value of N(H I) we obtain.…”

Section: Stellar Modelssupporting

confidence: 66%

“…Examination of Figure 4 shows that several other targets, such as TD1 32709 and LB 1566, exhibit similar behavior to WD1034+001 to some degree. This effect has also been seen in the published profiles for PG0038+199 and WD1034+001 (Werner et al 2017) and JL9 (Werner et al 2022), so it is not unique to our fitting procedure. Stellar model errors.…”

Section: N(h I) Error Analysismentioning

confidence: 53%

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A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium

Friedman

Chayer

Jenkins

et al. 2023

ApJ

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We present high signal-to-noise ratio measurements of the H i Lyα absorption line toward 16 Galactic targets that are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove stellar emission and absorption features and the methods used to account for all known sources of error in order to compute high-precision values of the H i column density with robust determinations of the uncertainties. When combined with H2 column densities from other sources, we find total H column densities ranging from 1020.01 to 1021.25 cm−2. Using deuterium column densities from Far Ultraviolet Spectroscopic Explorer observations we determine the D/H ratio along the sight lines. We confirm and strengthen the conclusion that D/H is spatially variable over these H i column density and target distance regimes, which predominantly probe the interstellar medium outside the Local Bubble. We discuss how these results affect models of Galactic chemical evolution. We also present an analysis of metal lines along the five sight lines for which we have high-resolution spectra and, along with results reported in the literature, discuss the corresponding column densities in the context of a generalized depletion analysis. We find that D/H is only weakly correlated with metal depletion and conclude that the spatial D/H variability is not solely due to dust depletion. A bifurcation of D/Htot as a function of depletion at high depletion levels provides modest support that deuterium-rich gas is infalling onto the Galactic plane.

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Section: Stellar Modelssupporting

confidence: 66%

Section: N(h I) Error Analysismentioning

confidence: 53%

A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium

Friedman

Chayer

Jenkins

et al. 2023

ApJ

View full text Add to dashboard Cite

show abstract

“…The effective temperature of JL 9 was increased from 68,820 K obtained from the optical fit alone to 75,000 K, as shown in Table 2, in order to reproduce the ionization balance of the Fe VI and Fe VII ions which are observed in the FUSE and STIS spectra. Werner et al (2022) came to a similar conclusion although their temperature and gravity are somewhat different with T eff = 80, 000 ± 5000 K and log g = 5.2 ± 0.3, but the error analysis described in Section 5.1 shows that this has a negligible effect on the value of N (H i) we obtain.…”

Section: Stellar Modelssupporting

confidence: 64%

A High Precision Survey of the D/H Ratio in the Nearby Interstellar Medium

D.¹,

Chayer²,

Jenkins³

et al. 2023

Preprint

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We present high S/N measurements of the H I Lyα absorption line toward 16 Galactic targets which are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove stellar emission and absorption features and the methods used to account for all known sources of error in order to compute high precision values of the H I column density with robust determinations of uncertainties. When combined with H 2 column densities from other sources, we find total H column densities ranging from 10 20.01 to 10 21.25 cm −2 . Using deuterium column densities from FUSE observations we determine the D/H ratio along the sight lines. We confirm and strengthen the conclusion that D/H is spatially variable over these H I column density and target distance regimes, which predominantly probe the ISM outside the Local Bubble. We discuss how these results affect models of Galactic chemical evolution. We also present an analysis of metal lines along the five sight lines for which we have high resolution spectra and, along with results reported in the literature, discuss the corresponding column densities in the context of a generalized depletion analysis. We find that D/H is only weakly correlated with metal depletion and conclude that the spatial D/H variability is not solely due to dust depletion. A bifurcation of D/H tot as a function of depletion at high depletion levels provides modest support that deuterium-rich gas is infalling onto the Galactic plane.

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“…PG 1159-035 is the prototype of the hot WD spectroscopic class called PG 1159, as well as the GW Vir class of pulsating variable stars (PG 1159-035 = GW Vir = DOV; McGraw et al 1979;Córsico et al 2019). The PG 1159 spectroscopic class is characterized by a strong H deficiency and high-excitation He II, C IV, O VI, and N V lines (e.g., Werner et al 1989;Sowicka et al 2021;Werner et al 2022). These are among the hottest pulsating stars known.…”

Section: Introductionmentioning

confidence: 99%

“…The PG 1159 spectroscopic class is characterized by a strong H deficiency and high-excitation He II, C IV, O VI and N V lines (e.g. Werner et al 1989;Sowicka et al 2021;Werner et al 2022). These are among the hottest pulsating stars known.…”

Section: Introductionmentioning

confidence: 99%

Kepler and TESS Observations of PG 1159-035

Córsico

Costa

Hermes

et al. 2022

ApJ

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PG 1159-035 is the prototype of the PG 1159 hot (pre-)white dwarf pulsators. This important object was observed during the Kepler satellite K2 mission for 69 days in 59 s cadence mode and by the TESS satellite for 25 days in 20 s cadence mode. We present a detailed asteroseismic analysis of those data. We identify a total of 107 frequencies representing 32 ℓ = 1 modes, 27 frequencies representing 12 ℓ = 2 modes, and eight combination frequencies. The combination frequencies and the modes with very high k values represent new detections. The multiplet structure reveals an average splitting of 4.0 ± 0.4 μHz for ℓ = 1 and 6.8 ± 0.2 μHz for ℓ = 2, indicating a rotation period of 1.4 ± 0.1 days in the region of period formation. In the Fourier transform of the light curve, we find a significant peak at 8.904 ± 0.003 μHz suggesting a surface rotation period of 1.299 ± 0.002 days. We also present evidence that the observed periods change on timescales shorter than those predicted by current evolutionary models. Our asteroseismic analysis finds an average period spacing for ℓ = 1 of 21.28 ± 0.02 s. The ℓ = 2 modes have a mean spacing of 12.97 ± 0.4 s. We performed a detailed asteroseismic fit by comparing the observed periods with those of evolutionary models. The best-fit model has T eff = 129, 600 ± 11 100 K, M * = 0.565 ± 0.024M ⊙, and log g = 7.41 − 0.54 + 0.38 , within the uncertainties of the spectroscopic determinations. We argue for future improvements in the current models, e.g., on the overshooting in the He-burning stage, as the best-fit model does not predict excitation for all of the pulsations detected in PG 1159-035.

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Non-local thermodynamic equilibrium spectral analysis of five hot, hydrogen-deficient pre-white dwarfs

Cited by 8 publications

References 59 publications

A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium

A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium

A High Precision Survey of the D/H Ratio in the Nearby Interstellar Medium

Kepler and TESS Observations of PG 1159-035

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