We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81–1.28 μm wavelength range of the zyJ bands, partially filling the gap between the optical (0.4–1.0 μm) and infrared (1.5–2.4 μm) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C i, P i, S i, K i). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He i 10830 Å absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of C i and S i in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet.
This study reports a probabilistic insight into the stellar-mass and supernovae (SNe) explosion energy of five CEMP-no stars' possible progenitors. As such, a direct comparison between the abundance ratios [X/Fe] of the light-elements and the predicted nucleosynthetic yields of SN of high-mass metal-free stars has been performed. This comparison suggests that the possible progenitors have a stellar-mass range of 11 − 22 M ⊙ and explosion energies of 0.3 − 1.8 × 10 51 erg.In addition, we investigate the kinematic signatures, derived from Gaia DR2, to conclude that these five CEMP-no stars have halo-like kinematic and do not enter the outer-halo region. In addition, we link the abundance patterns with kinematic signatures to investigate the Gaia-Sausage and Gaia-Sequoia memberships. This chemo-dynamical analysis suggests that these CEMP-no stars are neither Gaia-Sausage nor Gaia-Sequoia remnant stars, but another accretion event might be responsible for the contribution of these stars to the Galactic Halo.
We investigate the abundance of 19 F in the Sun through the nucleosynthesis scenario. In addition, we calculate the rate equations and reaction rates of the nucleosynthesis of 19 F at different temperature scale. Other important functions of this nucleosynthesis (nuclear partition function and statistical equilibrium conditions) are also obtained. The resulting stability of 19 F occurs at nucleus with A = 19 and Mass Excess = -1.4874 MeV. As a result, this will tend to a series of neutron captures and beta-decay until 19 F is produced. The reaction rate of 15 N (α, γ) 19 F was dominated by the contribution of three low-energy resonances, which enhanced the final 19 F abundance in the envelope.
Determining accurate effective temperatures of stars buried in the dust-obscured Galactic regions is extremely difficult from photometry. Fortunately, high-resolution infrared spectroscopy is a powerful tool for determining the temperatures of stars with no dependence on interstellar extinction. It has long been known that the depth ratios of temperature-sensitive and relatively insensitive spectral lines are excellent temperature indices. In this work, we provide the first extensive line depth ratio (LDR) method application in the infrared region that encompasses both the H and K bands (1.48 μm − 2.48 μm). We applied the LDR method to high-resolution (R ≃ 45,000) H- and K-band spectra of 110 stars obtained with the Immersion Grating Infrared Spectrograph. Our sample contained stars with 3200 < T eff (K) < 5500, 0.20 ≤ log g < 4.6, and −1.5 < [M/H] < 0.5. The application of this method in the K band yielded 21 new LDR–T eff relations. We also report five new LDR–T eff relations found in the H-band region, augmenting the relations already published by other groups. The temperatures found from our calibrations provide reliable temperatures within ∼70 K accuracy compared to spectral T eff values from the literature.
Timing data analysis of the bright X-ray source Cyg X-3 based on RXTE/PCA was presented. The observations were carried out in August 1996 and February 1997. All observations showed the 4. h 8 modulation due to the orbital period of the system with count rate ranging from ∼ 900 to ∼ 6000 cnt s −1. Almost all power spectra, the most sensitive timing results of Cyg X-3, may be well explained by pure Poisson noise above ∼ 0.2 Hz and a power-law below ∼ 0.2 Hz. During the February 1997, when the source was brightest in one part of the observations, it showed a temporary flickering-like behaviour with a period of ∼ 70 s. A detailed study of the timing properties of Cyg X-3 as a function of count rate, orbital phase and photon energy was presented. The flickering-like behaviour seemed to be a dominant effect in describing the level and shape of the power spectra below (< ∼ 0.2 Hz).
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