The abundance of potassium is derived from X-ray lines observed during flares by the RESIK instrument on the solar mission CORONAS-F between 3.53 A and 3.57 A. The lines include those emitted by He-like K and Li-like K dielectronic satellites, which have been synthesized using the CHIANTI atomic code and newly calculated atomic data. There is good agreement of observed and synthesized spectra, and the theoretical behavior of the spectra with varying temperature estimated from the ratio of the two GOES channels is correctly predicted. The observed fluxes of the He-like K resonance line per unit emission measure gives log A(K) = 5.86 (on a scale log A(H) = 12), with a total range of a factor 2.9. This is higher than photospheric abundance estimates by a factor 5.5, a slightly greater enhancement than for other elements with first ionization potential (FIP) less than about 10 eV. There is, then, the possibility that enrichment of low-FIP elements in coronal plasmas depends weakly on the value of the FIP which for K is extremely low (4.34 eV). Our work also suggests that fractionation of elements to form the FIP effect occurs in the low chromosphere rather than higher up, as in some models.
Lithium, Sodium, and Potassium Abundances in Sharp-Lined A-Type Stars
碱性元素丰度（Li，Na，K）是根据Li I 6708，Na I 5682/5688，和K I 7699谱线，通过考虑24颗尖线A型星的非LTE效应（v sin i < 50 km/s，7000 K < Teff <10000 K，许多显示不同程度的Am特性）确定的，基于在BOAO（韩国）和OAO（日本）获得的高色散和高信噪比光谱数据。我们发现了一个显着的趋势，A（Na）紧密标度与A（Fe）的Teff无关，这意味着Na成为富集类似于Fe根据程度的Am的特异性。关于锂，A（Li）大部分在~3和~3.5之间的范围内（即，几乎等于或略小于太阳系丰度3.3），在Teff < 8000 K时，随着Teff的降低，有微弱的下降趋势，尽管有几颗恒星例外地表现出明显更大的耗尽。钾的丰度也显示出明显的Tef依赖性，在这个意义上，晚A星的A（K）倾向于轻微的太阳下（可能与A（Fe）有弱的反相关），系统地从~5.0（Tef ~ 8500 K）下降到~4.6（Tef ~ 7500 K），而早A星的A（K）则保持在~5.0-5.2的太阳附近。这些观测事实可以作为任何旨在解释A型星化学异常的理论的重要约束。
Exploring the Milky Way stellar disk. Carbon, nitrogen, oxygen, sulphur, potassium, and copper abundances for 714 F- and G-type dwarf stars in the solar neighbourhood
Among the multiple stellar populations in globular clusters (GCs) the very high-temperature H-burning regime, able to produce elements up to potassium, is still poorly explored. Here we present the first abundance analysis of K in 42 giants of NGC 6715 (M 54) with homogeneous abundances of light elements previously derived in our FLAMES survey. Owing to the large mass and low metallicity, a large excess of K could be expected in this GC, which is located in the nucleus of the Sagittarius dwarf galaxy. We actually found a spread in [K/Fe] spanning about 1 dex, with [K/Fe] presenting a significa…
NGC 4833 is a metal-poor Galactic globular cluster (GC) whose multiple stellar populations present an extreme chemical composition. The Na-O anti-correlation is quite extended, which is in agreement with the long tail on the blue horizontal branch, and the large star-to-star variations in the [Mg/Fe] ratio span more than 0.5 dex. Recently, significant excesses of Ca and Sc with respect to field stars of a similar metallicity were also found, signaling the production of species forged in H-burning at a very high temperature in the polluters of the first generation in this cluster. Since an enha…
An extensive study on the potassium abundances of late-type stars was carried out by applying the non-LTE spectrum-fitting analysis to the K I resonance line at 7698.96A to a large sample of 160 FGK dwarfs and 328 late-G /early-K giants (including 89 giants in the Kepler field with seismologically known ages) belonging to the disk population (-1 < [Fe/H] < 0.5), which may provide important observational constraint on the nucleosynthesis history of K in the galactic disk. Special attention was paid to clarifying the observed behaviors of [K/Fe] in terms of [Fe/H] along with stellar age, and to …
Neutral Fe lines in metal-poor stars yield conflicting abundances depending on whether and how deviations from local thermodynamic equilibrium (LTE) are considered. We have collected new high resolution and high signal-to-noise ultraviolet (UV) spectra of three warm dwarf stars with [Fe/H] = -2.9 with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We locate archival UV spectra for three other warm dwarfs with [Fe/H] = -3.3, -2.2, and -1.6, supplemented with optical spectra for all six stars. We calculate stellar parameters using methods that are largely independent of …
A prevailing open problem in planetary nebulae research, and photoionized gaseous nebulae research at large, is the systematic discrepancies in electron temperatures and ionic abundances as derived from recombination and collisionally excited lines. Peimbert (1967) proposed the presence of 'temperature fluctuations' in these nebulae, but the apparent amplitude of such fluctuations, as deduced from spectral diagnostics and/or abundance discrepancy factors, remain unexplained by standard photoionization modeling. While this and other alternative models to explain the temperature and abundance di…
We have obtained new detailed abundances of the Fe-group elements Sc through Zn (Z=21-30) in three very metal-poor ([Fe/H] $\approx -3$) stars: BD 03 740, BD -13 3442 and CD -33 1173. High-resolution ultraviolet HST/STIS spectra in the wavelength range 2300-3050Å were gathered, and complemented by an assortment of optical echelle spectra. The analysis featured recent laboratory atomic data for number of neutral and ionized species for all Fe-group elements except Cu and Zn. A detailed examination of scandium, titanium, and vanadium abundances in large-sample spectroscopic surveys indicates tha…
We study the solar photospheric abundance of singly ionized neodymium (Nd II) using high resolution spectroscopic data obtained by Fourier transform spectrograph (FTS). Based on the Local Thermodynamical Equilibrium (LTE) assumption, a new value of Nd abundance is derived. We succeed to select of 51 solar Nd II lines with accurate transition probabilities measured experimentally by Den Hartog et al. (2003) and with accurate damping parameters are determined from literature. Relying on atomic data of Opacity Distribution Function (ODF), we construct theoretical photospheric solar model. The mea…
In this paper we discuss the calculation of chemical abundances in planetary nebulae and H II regions through ionization correction factors (ICFs). We review the first ICFs proposed in the literature based on ionization potential similarities and we present the most recent ICFs derived from large sample of photoionization models. We also discuss some of the considerations that have to be kept in mind when using ICFs to compute the chemical composition of ionized nebulae.
X-ray emission generated through solar-wind charge exchange (SWCX) is known to contaminate X-ray observation data, the amount of which is often significant or even dominant, particularly in the soft X-ray band, when the main target is comparatively weak diffuse sources, depending on the space weather during the observation. In particular, SWCX events caused by interplanetary coronal mass ejections (ICMEs) tend to be spectrally rich and to provide critical information about the metal abundance in the ICME plasma. We analyzed the SN1006 background data observed with Suzaku on 2005 September 11 s…
We present atmospheric parameters and abundances for chemical elements from carbon to barium in metal-poor stars in Segue 1 (seven stars), Coma Berenices (three stars), and Triangulum II (one star) ultra-faint dwarf galaxies (UFDs). The effective temperatures rely on new photometric observations in the visible and infra-red bands, obtained with the 2.5 m telescope of the SAI MSU Caucasian observatory. Abundances of up to fourteen chemical elements were derived under the non-local thermodynamic equilibrium (NLTE) line formation, and LTE abundances were obtained for up to five more elements. For…
