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NASA NTRS2012

Modeling Radar Scatter from Icy and Young Rough Lunar Craters

For lunar orbital synthetic aperture radars, such as the Chandrayaan Mini-RF operating at S- band (13-cm) wavelength and the Lunar Reconnaissance Orbiter Mini-RF operating at S- band and X-band (3-cm) wavelengths, it is important to understand the radar backscattering characteristics of the icy and young, rough craters. Assuming a mixing model consisting of diffuse and quasi-specular scattering components, we have modeled the opposite-sense circular (OC) and same-sense circular (SC) backscattering characteristics. The specular component, consisting of only OC echoes, represents the echoes from the surface and subsurface layers that are oriented perpendicular to the radar's line-of-sight. The diffuse component, consisting of both SC and OC echoes, represents the echoes associated with either rocks or ice. Also, diffuse echoes have backscatter that is proportional to the cosine of the incidence angle. We modeled how these two (specular and diffuse) radar scattering components could be modulated by factors such as surface roughness associated with young craters. We also modeled how ice radar scattering components could be modulated by a thin regolith covering, and/or by the situation where ice occupies small patches within a larger radar pixel. We tested this modeling by examining 4 nonpolar craters and 12 polar craters using LRO Mini-RF data. Results indicate that icy and young rough craters can be distinguished based upon their SC enhancements (Alpha) and OC enhancements (Gamma). In addition, we also examined the craters that have unusual circular polarization ratios (CPRs) that likely result from a double bounce mode of scattering. Blocky fresh craters, icy craters, and craters exhibiting double bounce scattering can be separated based on the values of Alpha, Gamma, the ratio of Alpha/Gamma and the weighted sum of Alpha and Gamma.

lunar craters↗
NASA NTRS2012

Measuring the Redshift Dependence of The Cosmic Microwave Background Monopole Temperature With Planck Data

We study the capability of Planck data to constrain deviations of the cosmic microwave background (CMB) blackbody temperature from adiabatic evolution using the thermal Sunyaev-Zeldovich anisotropy induced by clusters of galaxies. We consider two types of data sets depending on how the cosmological signal is removed: using a CMB template or using the 217 GHz map. We apply two different statistical estimators, based on the ratio of temperature anisotropies at two different frequencies and on a fit to the spectral variation of the cluster signal with frequency. The ratio method is biased if CMB residuals with amplitude approximately 1 microK or larger are present in the data, while residuals are not so critical for the fit method. To test for systematics, we construct a template from clusters drawn from a hydro-simulation included in the pre-launch Planck Sky Model. We demonstrate that, using a proprietary catalog of X-ray-selected clusters with measured redshifts, electron densities, and X-ray temperatures, we can constrain deviations of adiabatic evolution, measured by the parameter α in the redshift scaling T (z) = T0(1 + z)(sup 1−alpha), with an accuracy of sigma(sub alpha) = 0.011 in the most optimal case and with sigma alpha = 0.018 for a less optimal case. These results represent a factor of 2-3 improvement over similar measurements carried out using quasar spectral lines and a factor 6-20 with respect to earlier results using smaller cluster samples.

cosmic background radiation↗
NASA NTRS1980

A probabilistic approach to radiative energy loss calculations for optically thick atmospheres - Hydrogen lines and continua

An approximate probabilistic radiative transfer equation and the statistical equilibrium equations are simultaneously solved for a model hydrogen atom consisting of three bound levels and ionization continuum. The transfer equation for L-alpha, L-beta, H-alpha, and the Lyman continuum is explicitly solved assuming complete redistribution. The accuracy of this approach is tested by comparing source functions and radiative loss rates to values obtained with a method that solves the exact transfer equation. Two recent model solar-flare chromospheres are used for this test. It is shown that for the test atmospheres the probabilistic method gives values of the radiative loss rate that are characteristically good to a factor of 2. The advantage of this probabilistic approach is that it retains a description of the dominant physical processes of radiative transfer in the complete redistribution case, yet it achieves a major reduction in computational requirements.

Canfield, R. C.↗
NASA NTRS1990

Investigations of a turbulence-driven solar wind model

This work presents an investigation of the properties of the one-dimensional, two-fluid turbulence-driven solar wind model introduced by Hollweg and Johnson (1988). It is found that the model has serious difficulties in reproducing the observed high-speed wind at 1 AU. In particular, the model proton temperatures are lower than those observed by a factor of 2 or more, and the highest temperature models yield excessive wave intensities at 1 AU. It appears that the problem stems from the specific spatial distribution of heat deposition in the model. Thus this study does not rule out a turbulence-driven fast solar wind, since other forms of the turbulent evolution could probably achieve better results. A three-fluid version of the model is also presented to show that the addition of alpha particles does not significantly reduce the extreme proton temperatures displayed near the sun by the Hollweg and Johnson work. Finally, it is suggested that the additional heating needs to be located well beyond the critical point, implying that the heating mechanism for the fast solar wind is likely not the same as that heating the solar corona.

Isenberg, Philip A.↗
NASA NTRS2002

Chandra Observations of a Young Embedded Magnetic B Star in the p Ophiuchus Cloud

This paper reports the analysis of two Chandra X-ray observations of the young magnetic B star rho Ophiuchus S1. X-ray emission from the star was detected in both observations. The average flux is almost the same in both, but during each observation the flux shows significant time variations by a factor of two on timescales of 20-40 ksec. Each spectrum can be fit by either an absorbed power law model with a photon index of approx. -3 or a thin-thermal plasma model with a temperature of approx. 2 keV and an extremely low metal abundance (approx. less than 0.1 solar). The spectrum of the first observation has an apparent line feature at about 6.8 keV, which likely corresponds to highly ionized iron K alpha. In contrast, the spectrum of the second observation shows an anomalous edge absorption component at E approx. 1 keV. The continuum emission and log (L(sub X)/L(sub bol)) approx. -6 are similar to those of young intermediate-mass stars (Herbig Ae/Be stars) although the presence of the magnetic field inferred from the detection of non-thermal radio emission has drawn an analogy between rho Ophiuchus S1 and magnetic chemically peculiar (MCP) stars. If the X-ray emission is thermal, the highest plasma temperature observed is too high to be explained by the conventional theories of magnetic stars, and favors some kind of magnetic dynamo activity, while if the emission is nonthermal, it might be related to mass infall. The 6.8 keV line and 4 keV edge features are marginal but they give important information near the stellar body if they are real. Their physical interpretation is discussed.

Hamaguchi, Kenji↗
DOE OSTI2022

FLAG Review 2021

Abstract We review lattice results related to pion, kaon, D -meson, B -meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $$f_+(0)$$ f + ( 0 ) arising in the semileptonic $$K \rightarrow \pi $$ K → π transition at zero momentum transfer, as well as the decay constant ratio $$f_K/f_\pi $$ f K / f π and its consequences for the CKM matrix elements $$V_{us}$$ V us and $$V_{ud}$$ V ud . Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $$SU(2)_L\times SU(2)_R$$ S U ( 2 ) L × S U ( 2 ) R and $$SU(3)_L\times SU(3)_R$$ S U ( 3 ) L × S U ( 3 ) R Chiral Perturbation Theory. We review the determination of the $$B_K$$ B K parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $$m_c$$ m c and $$m_b$$ m b as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $$\alpha _s$$ α s . We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1981

PKS 2155-304 relativistically beamed synchrotron radiation from BL LAC object

The newly discovered BL Lacertae object, PKS 2155-304, was observed with the medium and high intensity energy detectors of the HEAO-1 A2 experiment. The variability by a factor of two in less than a day reported by Snyder, et al (1979) is confirmed. Two spectra, obtained a year apart, while the satellite was in scanning mode, are well fit by simple power laws with energy spectral index alpha sub 1 equals approximately 1.4. A third spectrum, of higher statistical quality, obtained while the satellite was pointed at its source, has has two components. An acceptable fit was obtained using a two power law model, with indices alpha sub 1 equals 2.0 (+1.2, -0.6) and alpha sub 2 equals -1.5 (+1.5, -2.3). An interpretation of the overall spectrum from radio through X-rays in terms of a synchrotron self-Compton model gives a good description of the data if allowance is made for relativistic beaming. Thus, from a consideration of the spectrum, combined with an estimate of the size of the source, the presence of jets is inferred without their observation.

Urry, C. M.↗
NASA NTRS1981

Boron and beryllium in Gamma Geminorum

Observations have been made of the B II resonance line at 1362 A in the A0 IV star Gamma Gem with the Princeton spectrometer on the Copernicus satellite at a spectral resolution of 0.05 A. Complementary ground-based observations of the Be II resonance lines at 3130 and 3131 A have been made at Mauna Kea Observatory with a comparable resolution. A model-atmosphere abundance analysis has been done which includes the effects of the lines that blend with the B II and Be II lines. Previous data on Alpha Lyr and Alpha CMa for B II (which blends with a V III feature) have been reanalyzed with the help of new photographic and Reticon data from Mauna Kea which enable the determination of the V abundance. The results show that Gamma Gem is depleted in B by a factor of 5-10 relative to Alpha Lyr and other normal B stars and depleted in Be by at least a factor of four. By comparison, the hot Am star Alpha CMa is B-deficient by about three orders of magnitude and Be-deficient by at least fifteen times. It is suggested that the abundance deficiencies are due to diffusion, and that Alpha CMa is intrinsically a slow rotator, and Gamma Gem is a slightly evolved slow rotator where some, but not all, of the B and Be has resurfaced.

Boesgaard, A. M.↗
NASA NTRS1981

Model for the circumstellar gas around alpha Orionis

Models are presented to explain the physical conditions in the circumstellar envelope surrounding the red supergiant Alpha Orionis. The models of the CO density and neutral atomic potassium density are calculated for the outer shell to reproduce simultaneously both the radio detection of CO and optical measurements of the amount of scattering by neutral potassium around Alpha Ori. CO and potassium loss rates of 7 x 10 to the 39th/sec and 8 x 10 to the 37th/sec are obtained, which imply a potassium to carbon ratio greater than that of the sun by about a factor of 25. The low carbon abundance may be attributed to extensive CNO processing, and, together with the potassium abundance, indicates a total mass loss rate of 0.000015 solar masses/year. The mass loss, mass and abundance properties of Alpha Ori suggest it to be the progenitor of a Type II supernova such as Cas A.

Jura, M.↗
NASA NTRS1995

The variability of the double-peaked Balmer lines in the active nucleus of NGC 1097

We present spectroscopic observations of the nucleus of the Seyfert/low-ionization nuclear emission-line region galaxy NGC 1097 spanning the period 1991-1994. The goal was to monitor anticipated variations of the broad, double-peaked Balmer lines which appeared abruptly in 1991. We find that the broad Balmer lines have varied significantly over the monitoring period, both in their integrated fluxes and in their profile shapes. The integrated H-alpha flux has decreased by a factor of 2, the (H-alpha)/(H-beta) ratio has increased, and the originally asymmetric H-alpha profile has become symmetric. The decline of the H-alpha flux and the change in the (H-alpha)/(H-beta) ratio can be interpreted as consequences of either increased obscuration along the line of sight, or a decline in the ionizing continuum, but neither of these scenarios can account for the change in profile shapes. A model attributing the line emission to a precessing elliptical ring around a 10(exp 6) solar mass nuclear black hole can reproduce the observed profile variations. In this scenario, the line-emitting ring is the result of the tidal disruption of a star by the black hole. Alternative scenarios associating the broad-line emission with a collimated bipolar outflow also remain viable, but binary black holes and inhomogeneous accretion disks are disfavored by the observed pattern of variability.

Storchi-Bergmann, Thaisa↗
NASA NTRS1983

H I Lyman-alpha in the sun - The effects of partial redistribution in the line wings

A form for the Lyman-alpha redistribution function that is modified to include the effects of collisional coupling between different energy states is presented. It is noted that this extends the work of Yelnik et al. (1981) and Roussel-Dupre(1982). By separating the source function into its primary components at all heights, the formation of Lyman-alpha radiation is investigated in detail. Frequencies in the line wing can be mapped back in such a way that the heights of formation for a change in lambda of plus or minus 0.5-6 A span the entire solar chromosphere. The usefulness of the Lyman-alpha wing as an atmospheric probe, however, is limited by long thermalization lengths, which result from almost coherent scattering outside of the Doppler core. When the line profiles calculated from the chromospheric models of Vernazza et al. (1981) are compared with the quiet-sun observations of Roussel-Dupre, agreement is found in integrated core intensities and in the line wing shape and normalized center-to-limb behavior. The calculated wing intensities, however, are a factor of four too small.

Roussel-Dupre, D.↗
NASA NTRS1994

Lick optical spectra of quasar HS 1946+7658 at 10 kilometers per second resolution Lyman-alpha forest and metal absorption systems

We present optical spectra of the most luminous known quasi stellar object (QSO) HS 1946+7658 (z(sub em) = 3.051). Our spectra have both full wavelength coverage, 3240-10570 A, and in selected regions, either high signal-to-noise ratio, SNR approximately equals 40-100, or unusually high approximately 10 km/sec resolution, and in parts of the Ly alpha forest and to the red of Ly alpha emission they are among the best published. We find 113 Ly alpha systems and six metal-line systems, three of which are new. The metal systems at z(sub abs) = 2.844 and 3.050 have complex velocity structure with four and three prominent components, respectively. We find that the system at z(sub abs) = 2.844 is a damped Ly alpha absorption (DLA) system, with a neutral hydrogen column density of log N(H I) = 20.2 +/- 0.4, and it is the cause of the Lyman limit break at lambda approximately equals 3520 A. We believe that most of the H I column density in this system is in z(sub abs) = 2.8443 component which shows the strongest low-ionization absorption lines. The metal abundance in the gas phase of the system is (M/H) approximately equals -2.6 +/- 0.3, with a best estimate of (M/H) = -2.8, with ionizaion parameter log gamma = -2.75, from a photoionization model. The ratios of the logarithmic abundances of C, O, Al, and Si are all within a factor of 2 of solar, which is important for two reasons. First, we believe that the gas abundances which we measure are close to the total abundances, because the ratio of aluminum to other elements is near cosmic, and Al is a refractory element which depletes very readily like chromium, in the interstellar medium. Second, we do not see the enhancement of O with respect to C of (O/C) approximately equals 0.5-0.9 reported in three partial Lyman limit systems by Reimers et al. (1992) and Vogel & Reimers (1993); we measure (O/C) = -0.06 for observed ions and (O/C) approximately equals 0.2 after ionization corrections, which is consistent with solar abundances. We see C II*(lambda 1335) offset by 15 km/sec with respect to C II(lambda 1334), presumably because the gas density varies from 2 to 8 cm(exp -3) with changing velocity in the DLA system. These densities imply that the damped component is 6-25 pc thick, which is reasonable for a single cloud in a cold spiral disk. They also imply that the cloud is relatively highly ionized with more C III than C II, more O III than O I, and log N(H I) = 20.72, which is 3 times the H I column. The system at z(abs) = 1.7382 is also believed to be damped with N(H I) approximately equals 10(exp 21) cm(exp -2), because we see Cr II, but its Ly alpha line will never be seen because it is below the Lyman limit of the other DLA system. We see a 2.6 sigma lack of Ly alpha forest lines well away from the QSO redshift, which may be a chance fluctuation. We also see a correlation between column density N(H I) and Doppler parameter b for 96 unsaturated Ly Alpha forest absorption lines, and although this correlation persists in the 36 Ly alpha lines which lie in regions where the SNR approximately equals 8-16, we agree with Rauch et al. (1993) that it is probably a bogus effect of low supernova remnant (SNR). The same applies to lines with very low b values: in regions where SNR less than or equal to 8 we see many Ly alpha lines which appear to have 10 less than or equal to b less than or equal to 20, but when 8 less than or equal to SNR less than or equal to 16 we see only one line with b less than or equal to 15 km/sec, and two others which we believe have b less than or equal to 20, with values of 20 and 16 km/sec. Traditional Ly alpha line samples which include all lines which have W/sigma(W) greater than or equal to 4 are not adequate to explore the distribution of the properties of individual clouds, because we need much higher (W/sigma(W)) and SNR to avoid the strong biases.

Fan, Xiao-Ming↗
NASA NTRS1994

The X-ray spectrum of the highly polarized quasar PKS 1502+106

We report the detection and spectrum of the distant (z = 1.839), highly polarized quasar PKS 1502+106 in the X-ray band based on data collected over the period 1990-1994 using ROSAT and ASCA. We find the source to exhibit intensity variations of a factor approximately greater than 2 at 1 keV on timescales of years, small compared to the variability observed historically in the radio, millimeter, and optical bands. The (energy) spectral index is found in the range 0.4 approximately less than alpha(sub x) approximately less than 0.8 (at 90% confidence). Its multiwaveband spectral index is broadly consistent with other highly polarized quasars (HPQs). From the application of an inhomogeneous synchrotron self-Compton (SSC) jet we find that a model similar to that proposed for 3C 279 is consistent with the multiwaveband spectrum. We suggest that a change in the energy injection and/or transport mechanisms within such a jet could easily result in PKS 1502+106 being detectable at gamma-ray energies.

George, I. M.↗
NASA NTRSDate not supplied

Phosphate (U-Th)/He Thermochronology of Apollo 14 Melt Breccia 14311

Our ability to confidently characterize the impact history of the inner solar system is limited by discrepancies in radiometric dates and age interpretations for lunar rocks, impact melts, and recovered meteorites. It is therefore important to explore different thermally sensitive radiometric systems to unravel the timing and extent of the long term impact flux. Low-temperature thermochronology of lunar samples has the potential to provide more complementary geochronological datasets and further test dynamical models related to the evolution of the inner solar system (e.g., [1]). (U-Th)/He dating is based on the production of 4He atoms by radioactive alpha decay of U and Th (and to a lesser extent, Sm) in a crystal and the thermally activated volumetric diffusion of those 4He nuclides. At high temperatures, the crystal is an open system from which 4He can escape; at lower temperatures, 4He may be retained. This retention temperature depends on factors such as crystal structure and volume fraction of radiation damage in the crystal (e.g., [2, 3]), but is significantly lower for phosphate minerals compared to the diffusion of the radiogenic daughter products in other widely used chronometric systems (e.g., ~75°C in terrestrial apatite (U-Th)/He vs. ~500°C in apatite U-Th-Pb vs. ~900°C in zircon U-Th-Pb chronometry). Phosphate (U-Th)/He dating has been used to decipher peak temperatures and cooling rates related to terrestrial impact events (e.g., [4]). Pairing a low-temperature thermochronometer with higher-temperature approaches (i.e., a combined 207Pb-206Pb and (U-Th)/He approach), can therefore resolve multiple impact ages within a given sample or even grain. However, despite its potential, phosphate (U-Th)/He dating has not been reported on any lunar samples. Here we present the first lunar phosphate (U-Th)/He thermochronology on an Apollo 14 impact melt-breccia.

C A Diaz↗
NASA NTRS1994

On the decay of outbursts in dwarf novae nad X-ray novae

We perform computations using a time-dependent model for the accretion disk limit-cycle mechanism to examine the decay of the optical light following the peak of a dwarf nova outburst. We present the results of a parameter study of the physical input variables which affect the decay rate. In the model, the decay is brought about by a cooling transition front which begins at large radii in the disk and moves inward. The nature of the decay is strongly influenced by the radial dependence of the accretion disk viscosity parameter alpha. To obtain exponential decays for typical dwarf nova parameters, we require alpha proportional to r(exp epsilon(sub 0)), where epsilon(sub 0) approximately = 0.3-0.4. The exact value of epsilon(sub 0) which produces exponential decays depends on factors such as the mass of the accreting star and the inner radius of the accretion disk. Therefore, the observed ubiquity of exponential decays in two different types of systems (dwarf novae and X-ray novae) leads us to believe that alpha is an unnatural scaling for the viscosity. The physics of the cooling transition front must be self-regulating in that the timescale (-parital derivative of lnSigma(r)/partial derivative +)(exp -1) (where Sigma is the surface density) for mass extraction across the front remains constant. This may be consistent with a scaling alpha proportional to (h/r)(exp n), where h is the local disk semi-thickness and n approximately 1-2. As regards the speed of the cooling front, we find v(sub F)(r) proportional to r(exp p), where p approximately 3 at large radii, with an abrupt transition to p approximately 0 at some smaller radius. The r(exp 3) dependence is much steeper than has been found by previous workers and appears to result from the strong variation of specific heat within the cooling front when the front resides at a large radius in the disk. The outflow of disk material across the cooling front causes a significant departure of dln T(sub dff0/dln r from the standard value of -0.75 (expected from steady state accretion) within about 0.2 dex in radius of the break associated with the cooling front -- T(sub eff) aproximately 10(exp 3.9) K (r/10(exp 10 cm)) (exp -0.1). These effects should be observable with eclipse mapping. Finally, it appears that the relatively slow decay rate for the optical flux in the 1975 outburst of A0620-00 can be accounted for if the primary is a approximately 10 Solar mass black hole.

Cannizzo, John K.↗
NASA NTRS2012

Concentration Effects and Ion Properties Controlling the Fractionation of Halides during Aerosol Formation

During the aerosolization process at the sea surface, halides are incorporated into aerosol droplets, where they may play an important role in tropospheric ozone chemistry. Although this process may significantly contribute to the formation of reactive gas phase molecular halogens, little is known about the environmental factors that control how halides selectively accumulate at the air−water interface. In this study, the production of sea spray aerosol is simulated using electrospray ionization (ESI) of 100 nM equimolar solutions of NaCl, NaBr, NaI, NaNO2, NaNO3, NaClO4, and NaIO4. The microdroplets generated are analyzed by mass spectrometry to study the comparative enrichment of anions (f (Isub x-)) and their correlation with ion properties. Although no correlation exists between f (sub x-) and the limiting equivalent ionic conductivity, the correlation coefficient of the linear fit with the size of the anions R(sub x-), dehydration free-energy ΔGdehyd, and polarizability alpha, follows the order: (R(sub x-)(exp −2)) > (R(sub x-)(exp −1)) >(R(sub x-) > delta G(sub dehyd) > alpha. The same pure physical process is observed in H2O and D2O. The factor f (sub x-) does not change with pH (6.8−8.6), counterion (Li+, Na+, K+, and Cs+) substitution effects, or solvent polarity changes in methanol − and ethanol−water mixtures (0 <= xH2O <= 1). Sodium polysorbate 20 surfactant is used to modify the structure of the interface. Despite the observed enrichment of I− on the air−water interface of equimolar solutions, our results of seawater mimic samples agree with a model in which the interfacial composition is increasingly enriched in I− < Br− < Cl− over the oceanic boundary layer due to concentration effects in sea spray aerosol formation.

iodine↗
NASA NTRS1992

Mass loss in main-sequence A-type stars?

We present new observations of the H-alpha line profile for five main-sequence A-type stars, where very high SNRs were achieved. A search for weak asymmetries was carried out to detect a stellar wind, but the many telluric absorption lines in this range prevent us from taking the full benefit of the high SNRs. This situation was improved by modeling the telluric absorptions to remove them from the observed spectra, but the H-alpha profiles were nevertheless found to be quite symmetric. We calculated the profile of the H-alpha line for a grid of model atmospheres of an A-type star including a weak wind, in order to assess an upper limit on the mass loss rate. The asymmetry is found to be sensitive to the velocity law and to the turbulent velocity of the wind, but its first moment depends much less on them. The upper limits deduced on the mass loss rate are between 1 and 2 x 10 exp -10 solar mass/yr. An improvement up to a factor 10 could be anticipated if new observations could be secured from a much drier location, achieving similar SNRs.

Lanz, T.↗
NASA NTRS1993

The boron abundance of Procyon

The B I 2496.8 A resonance line and HST/GHRS echelle spectra are used with model atmospheres and synthetic spectra to derive the B abundance of the F dwarfs Procyon (Alpha Canis Minoris), Theta Ursae Majoris, and Iota Pegasi. The B abundance of Theta UMa and Iota Peg is similar to that derived by Boesgaard and Heacox (1978) from the B II resonance line in spectra of A- and B-type stars. These two dwarfs show normal abundances of Li, Be, and B. Procyon, which is highly depleted in Li and Be, is depleted in B by a factor of at least 3. Comparison of the spectra of Procyon and the halo dwarf HD 140283 shows that the B abundance assigned by Duncan et al. (1992) to three halo dwarfs is not greatly overestimated as a result of contamination of the B I line by an unidentified line.

Lemke, Michael↗