Douglas K. Duncan

Douglas K. Duncan
University of Colorado Boulder | CUB · Department of Astrophysical and Planetary Sciences

About

93
Publications
16,421
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
6,261
Citations

Publications

Publications (93)
Article
There is considerable pressure on faculty members to use technology in teaching. Students also bring technology into class in the form of laptop computers, smart phones, and iPads. Does this technology increase or decrease learning? We report two years of data studying 14 different classes with a total of approximately 1200 students. We find that,...
Article
Full-text available
The recent increase in the use of digital devices such as laptop computers, iPads and web-enabled cell phones has generated concern about how technologies affect student performance. Combining observation, survey, and interview data, this research assesses the effects of technology use for student attitudes and learning. Data were gathered in eight...
Article
Full-text available
Student attitudes about learning science and student ideas about the nature of science were compared at the end of two astronomy courses taught in Fall 2007, a course with a traditional astronomy curriculum and a transformed course, whose traditional astronomy curriculum was supplemented by an embedded curriculum that explicitly addressed the natur...
Article
Full-text available
This is our fourth paper in our five paper series describing our national study of general education astronomy students' conceptual and reasoning difficulties with cosmology. While previous papers in this series focused on the processes by which we collected and quantitatively analyzed our data, this paper presents the most common pre-instruction c...
Article
This is the final paper in a five-paper series describing our national study of the teaching and learning of cosmology in general education astronomy college-level courses. A significant portion of this work was dedicated to the development of five new Lecture-Tutorials that focus on addressing the conceptual and reasoning difficulties that our res...
Article
Full-text available
This is the first in a series of five articles describing a national study of general education astronomy students' conceptual and reasoning difficulties with cosmology. In this paper, we describe the process by which we designed four new surveys to assess general education astronomy students' conceptual cosmology knowledge. These surveys focused o...
Article
Full-text available
This is the third of five papers detailing our national study of general education astronomy students' conceptual and reasoning difficulties with cosmology. In this paper, we use item response theory to analyze students' responses to three out of the four conceptual cosmology surveys we developed. The specific item response theory model we use is k...
Article
For the past two years, we have conducted fundamental research into Astro 101 students' conceptual and reasoning difficulties in cosmology. To date, we have analyzed the responses of over 2000 students from institutions across the United States to questions on the Big Bang, the expansion and evolution of the universe, and the evidence for dark matt...
Article
The Department of Astrophysical and Planetary sciences at the University of Colorado has increasingly been incorporating research-based science education practices. The Colorado physics education research (PER) group is now one of the largest and most productive in the nation. It includes the work of Nobel laureate Carl Wieman's Science Education I...
Article
Full-text available
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to obtain spectra of the 2500 Å region in eight stars with metallicities ranging from [Fe/H] = -0.4 to -3.0, including the most metal-poor star ever observed for boron. Spectrum synthesis utilizing latest Kurucz model atmospheres has been used to deter...
Article
Full-text available
High signal-to-noise ratio Hubble Space Telescope Goddard High-Resolution Spectrograph spectra of α Centauri A (spectral type G2 V) and α Centauri B (spectral type K1 V) have been analyzed in the Be II λ3130 spectral region. Both stars offer an excellent opportunity for testing predictions of ⁹Be destruction since they are nearby, have a well-deter...
Article
Full-text available
The boron abundances of two giants and one turnoff star in the Hyades, and the field K0 III giant β Gem, have been measured from spectra obtained with the Hubble Space Telescope in the vicinity of the B I lines near 2500 Å. This provides a test of the dilution of giant envelopes predicted by standard stellar evolutionary models: since B is destroye...
Article
Full-text available
Data in the λ2090 B region of HD 76932 have been obtained at a high signal-to-noise ratio using the Hubble Space Telescope Goddard High-Resolution Spectrograph echelle at a resolution of 90,000. This wavelength region has been previously identified as a likely candidate for observing the 11B/10B isotopic splitting. The observations do not match a c...
Article
Full-text available
We present results of an analysis of the boron spectral region (2500 Å) in the metal-poor star HD 160617, observed with the Goddard High Resolution Spectrograph of the Hubble Space Telescope. HD 160617 has a metallicity of [Fe/H] ≈ -1.8, a Teff ≈ 5900 K, and a log g ≈ 3.5. Its Li abundance is the normal, primordial "Spite plateau" value log (Li) ≈...
Article
Surveys of those who teach Astro 101 say that increasing students' understanding of the nature and process of science is an important goal. It is also one of the justifications for the "breadth requirement'' that supports most of the Astro 101 enterprise in the US. However, little work has been done to measure if this goal is achieved. We interview...
Article
We present an optical study of four 45' × 45' fields centered ~05 east, west, north, and south of the Orion Nebula Cluster center. We have measured V and IC photometry for ~5000 stars, and U photometry for ~1600 of these. We have obtained spectral classifications for ~300 of the stars with UVIC photometry plus an additional ~200 stars located outsi...
Article
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during the years 1966-1983. These results are derived from 65,263 individual observations of 1296 stars. For each star, for each observing season, the maximum, minimum, mean, and variation of the instrumental H and K ind...
Article
Full-text available
The Space Telescope Imaging Spectrograph (STIS) obtained high resolution echelle spectra of the nearby G2 V star Alpha Centauri A covering the entire 1133-3150 Angstrom region with very high signal/noise. This data set provides what is likely the best approximation to the spectrum of the Sun viewed as a star because it is a full disk spectrum with...
Article
This table is part of a paper is which a study of the alpha Cen A spectrum recorded with the E140 grating by HST/STIS between 1140 and 1670{AA} is presented. In this spectrum the authors have identified a total of 662 emission features of which 77 are due to blends of two or more lines, 71 are due to unidentified transitions, and 514 are identified...
Article
Full-text available
We describe and analyze HST/STIS observations of the G2 V star alpha Centauri A (alpha Cen A, HD 128620), a star similar to the Sun. The high resolution echelle spectra obtained with the E140H and E230H gratings cover the complete spectral range 1133-3150 Angstrom with a resolution of 2.6 km/s, an absolute flux calibration accurate to +/-5%, and an...
Article
Despite being the most abundant element in the Galaxy and the fact that the first determinations of its abundance in large samples of stars date back to the 60s, the evolution of oxygen along the Galactic history is still quite puzzling. In short, the results obtained by analyzing different oxygen abundance indicators (the OI triplet, the forbidden...
Article
HST observations have led to new theories of how cosmic rays (CRs) rich in CNO in regions of massive star formation may contribute to the formation of the light elements Li, Be, and B. The neutrino process in SN, which has never been experimentally verified, should also produce boron, but only 11B, yielding a very different isotopic ratio than CR s...
Article
Type II supernovae (SNII) are expected to be the site of nucleosynthesis at very low [Fe/H]; one fairly robust prediction of SNII models is that 11B is produced from 12C via neutrino spallation. We can test these models by observing 11B/10B in low-metallicity stars.
Article
Full-text available
A sample of 7 new stars ranging in metallicity from [Fe/H]=-2.0 to [Fe/H]=-0.75 has been analyzed in the boron spectral region. The spectra were observed with the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST). The targets were selected on the basis of their lithium and beryllium abundances in order to investigate i...
Article
Many astronomers now have some involvement in K-12 education, either through their children, through large projects with an education or outreach office, or through an educational component to their own grants. Some may need to incorporate education components into future proposals. For those new to education, it can be difficult to decide how best...
Article
This workshop is designed to assist middle and high school teachers and astronomers who work with them or who teach introductory college courses in doing hands-on activities on astronomical topics. We will show the pioneering video, "A Private Universe ," on how students learn (and don't learn) science, and then discuss ways of aligning work in the...
Article
Full-text available
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to observe the boron 2500 A region of BD-13 3442. At a metallicity of [Fe/H]=-3.00, this is the most metal-poor star ever observed for B. Nearly 26 hours of exposure time resulted in a detection. Spectrum synthesis using the latest Kurucz model atmosp...
Article
An overview of the discussions of the working group on Low-Z stars is presented. Key questions addressed include how the abundances of lithium observed in these stars should be compared to that produced in the Big Bang. Evidence for and against a small star-to-star variation in Li abundances is reviewed, and whether such a variation, if real, neces...
Article
Full-text available
Data in the lambda2090 B region of HD 76932 were obtained using the HST GHRS echelle at a resolution of 90,000. This wavelength region has been previously identified as a likely candidate for observing the 11B/10B isotopic splitting (Johansson et al. 1993). However, data presented here reveal that the B line in question is blended with unknown stel...
Article
Full-text available
Data in the lambda 2090 B region of HD 76932 were obtained using the HST GHRS echelle at a resolution of 90,000. This wavelength region has been previously identified as a likely candidate for observing the (11) B/(10) B isotopic splitting (Johansson et al. 1993). Data presented here provides some constraints on the isotopic ratio, but it is not ce...
Article
High signal-to-noise (200 to 1) Hubble Space Telescope GHRS spectra of α Cen A (spectral type G2 V) and α Cen B (spectral type K1 V) i the Be II λ3130 region have been analyzed, for the purpose of making a precise determination of light element destruction in stars of approximately the same mass of the Sun's. Light element abundances in this stella...
Article
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to obtain spectra of the boron 2500 Å region in a total of 11 stars ranging from to −2.96, including the most metal-poor star ever observed for B. Spectrum synthesis was used to determine the boron abundance for each star, with particular attention pai...
Article
Stars of a wide range of metallicity have been observed and analyzed in the spectral region of the BeII resonant doublet (~3130 Angstroms), with the aim of understanding the primary mechanism(s) of Be production during the galactic history and of investigating the structure of the outermost atmospheric layers in order to constrain which mixing and...
Article
Lithium abundances have been determined for 27 stars in the Orion Nebula region with V=12-14, and (B-V)=0.5-1.2. All of the stars are within 20 arc minutes of the Trapezium; they range from approximately 1.0 to 1.6 M_&sun; and from 10(6) to 10(7) years old. Approximate chronological ordering of the stars is possible from their location in the HR di...
Article
Since the 1970s it has been believed that the light elements Li, Be, and B are made by the spallation of cosmic rays (CRs; primarily energetic protons and alpha particles) on nuclei of C, N, and O in the interstellar medium. Abundances of the light elements have in fact been used to infer the existence of a large flux of low energy CRs which are ke...
Article
Observations of the BI 2500 Angstroms line have been obtained with the Goddard High Resolution Spectrograph of the Hubble Space Telescope in 6 intermediate metal poor stars. Metallicities of the stars range from [Fe/H] = -0.35 to -2.5. The latest Kurucz model atmospheres and a single optimized line list are used to produce synthetic spectra and det...
Article
Full-text available
The fluxes in passbands 0.1 nm wide and centered on the Ca II H and K emission cores have been monitored in 111 stars of spectral type F2-M2 on or near the main sequence in a continuation of an observing program started by O. C. Wilson. Most of the measurements began in 1966, with observations scheduled monthly until 1980, when observations were sc...
Article
Spectra of two of the Hyades giants ϵ Tau (HD 28305) and δ 1 Tau (HD 27697), the reference K0II giant β Gem (HD 62509), and the Hyades main-sequence F star 45 Tau (vB 14) have been obtained with the Hubble Space Telescope. Boron abundances were determined from spectrum synthesis of the region near 2500Å. Since B is destroyed by (p,α) reactions at a...
Article
Full-text available
Spectra of two of the Hyades giants epsilon Tau (HD 28305) and delta (1) Tau (HD 27697) and the K0II giant beta Gem (HD 62509) have been obtained with the G270M grating of the GHRS spectrograph of the Hubble Space Telescope. A Hyades main sequence F star near the turnoff was also observed. Boron abundances were determined from spectrum synthesis of...
Article
Full-text available
New low noise, HST High Resolution Spectrometer boron B I lambda2496 observations are presented of the F6 subgiant 110 Her and the Hyades F2 dwarf 45 Tau (vB 14). 45 Tau has previously been shown to have normal lithium and beryllium abundances for a Hyades F2 star. In contrast, 110 Her is deficient in lithium by more than two orders of magnitude an...
Article
Full-text available
Evidence is presented to the effect that there exists a small dispersion in the lithium abundances of extreme halo dwarfs. This dispersion cannot be accounted for by standard stellar models alone, particularly toward the turnoff, and would thus require early differential Galactic Li enrichment, perhaps independent of metallicity. The magnitude of t...
Article
Full-text available
New measurements of lithium in more than 100 Pleiades F, G, and K dwarfs are reported. Abundances are determined from spectrum synthesis fits to the data as well as from use of new covers of growth from the Li 6708-A feature. It is argued that most Late-F and early-G dwarfs in the Pleiades are consistent with the tight N(Li) vs mass relation seen i...
Article
B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy co...
Article
An attempt is made to formulate the relationship between age and chromospheric emission (CE) in late-type dwarf stars. Evidence is reviewed that a deterministic relationship of this type actually exists, and that for stars of known age, either a power-law relation or a curve corresponding to a constant star formation rate fits equally well. Further...
Article
Summaries are presented of the photoelectric measurements of stellar Ca II H and K line intensity made at Mount Wilson Observatory during the years 1966-1983. These results are derived from 65,263 individual observations of 1296 stars. For each star, for each observing season, the maximum, minimum, mean, and variation of the instrumental H and K in...
Article
The Li abundance of the T Tauri star BP Tau is determined from both the Li I 6707 and 6103 features, using high-accuracy observations and recent model atmospheres. Other work, based solely on analysis of the lambda-6707 line, has found very high Li abundances in T Tauri stars. We find a significant difference between the abundances derived from the...
Article
The evolution of rotation on approach to the main sequence (MS) is studied in about 50 stars in the Orion Nebula region with V = 12-14, B-V = 0.6-1.2. The observed distribution of v sin i shows a range from less than 15 km/s to about 50 km/s. A wide range of v sin i is present at all evolutionary phases, and this apparently can be traced back to th...
Article
Full-text available
Stars in the central region of the old open cluster M67 were monitored for stability using CCD, time-resolved photometry. Five sites with 1 m class telescopes participated in an intensive monitoring effort, yielding contiguous 14 night coverage with 1 min temporal resolution. Noise levels to 0.0008 mag variation relative to an ensemble mean were at...
Article
Curves of growth are presented for both the Li-I 6707 and 6103 features in T-Tauri stars. In such strong Li-lined stars, the subordinate 6103 A feature should be visible, and it is seen in high-accuracy observations of the star BP Tau. This weaker line should be less susceptible to systematic errors in abundance determinations. A significant differ...
Article
Full-text available
High-precision differential b, y photometric observations of 24 Hyades stars, spectral types F4 V to K8 V, were made at Lowell Observatory during late 1983 and early 1984. It was found that all 18 stars of spectral type F8 V or later in this sample were variable, confirming that low-level photometric variability is a ubiquitous and persistent chara...
Article
Four rapidly rotating early-K dwarfs in the Pleiades are shown to contain an order of magnitude more Li than four slow rotators of the same spectral type, as would be expected if they were systematically younger. This supports the idea that late-type stars first arrive on the main sequence with Vrot ⪆ 100 km s-1, that they spin down to Vrot ⪉ 10 km...
Article
Full-text available
Spectroscopic observations are reported for 23 population II subdwarfs (selected for age homogeneity) and 31 other stars (mainly population I F and G dwarfs). The spectra were obtained in the 670.7-nm line of Li I using coude spectrographs on the 2.7-m reflector at McDonald Observatory, the 3.0-m reflector at Lick Observatory, and the 4-m Mayall re...
Article
Full-text available
Li abundance is determined for 23 halo subdwarfs. About half of the stars show [Fe/H] V > 160 km s−1 Li appears to be present in all our halo stars, with an abundance within about ± 0.2 dex of the value logn (Li) = 2.0 found by Spite & Spite (1982). Thus our results provide confirmation of the main conclusion of Spite & Spite.
Article
We have observed 23 halo stars with space velocities\( \left| {\begin{array}{*{20}{c}} \to \\ {{v_{LSR}}} \end{array}} \right| \geqslant 100\,km\,{s^{ - 1}} \) and metallicities [Fe/H] ≤ -0.6, Twelve of these 23 show the more extreme properties \( \left| {\begin{array}{*{20}{c}} \to \\ {{v_{LSR}}} \end{array}} \right| \geqslant 160\,km\,{s^{ - 1}}...
Article
We have observed 23 halo stars with space velocities and metallicities [Fe/H] ≤ −0.6. Twelve of these 23 show the more extreme properties and [Fe/H] ≤ −1.4 and should therefore constitute an especially old, homogeneous subgroup. The principal results for these 12 extreme halo stars and 5 similar stars observed in previous studies are that (1) a sin...
Article
The relative strength of the chromospheric Ca II H and K emission cores has been monitored on a near- nightly basis during several seasons in a variety of cool stars, predominantly those lower-main-sequence stars observed by Wilson for long-term chromospheric activity fluctuations. From initial data obtained in 1980, rotation rates had been inferre...
Article
H-alpha emission having a full width at its base of 700 km/s is observed in the main-sequence K star, H II 1883, confirming the report by Stauffer et al. (1984). Both the centroid and the width of the H-alpha emission vary synchronously with the 0.24 day rotation period of this Pleiades star. Based on the ratio H-alpha/H-beta, the absence of forbid...
Article
The H alpha emission with full width at its base of 700 km/sec was observed in the young main sequence K star, HII 1833 of similar mass to the Sun. The centroid and the width of the emission vary synchronously with the 0.24-day rotation period or this Pleiades star. Based on the ratio H alpha/H beta, the absence of forbidden lines, and the inferred...
Article
Evidence of global p-mode oscillations in the K2 V star Epsilon Eridani, based on observed time variations in the Ca II H and K emission lines, is presented. Power spectra of time series of Ca II intensity measures reveal a number of peaks spaced at about 86 and 172 micro-Hz. The 172 micro-Hz spacing is significantly larger than the corresponding s...
Article
The identity of chromospheric Ca II H- and K-line emission has been monitored for two seasons in a large sample of Hyades F and G dwarfs. Mean emission levels vary smoothly with spectral type, suggesting that the rotation rate at a given spectral type varies relatively little, and that the rotation rate decreases smoothly as a function of mass. In...
Article
High-precision differential photometric observations of 32 Hyades stars, spectral type F4 V to K1 V, were obtained at Lowell Observatory over a five-month season during late 1982 and early 1983. Contemporaneous Ca II H+K emission flux measurements for 30 of these stars were made at Mount Wilson Observatory. Fifteen (possibly 18) of these stars, all...
Article
International Ultraviolet Explorer satellite measurements of the Mg II chromospheric emission from a sample of late-type dwarfs with known rotational periods are presented. The ratio of chromospheric to photospheric luminosity for the late-G and K type stars in this sample can be fitted within the probable errors by a single function of rotational...
Article
A sample of field F and G dwarfs of known ages is presented. All the dwarfs are secondaries of visual binaries in which the temperature and gravity of the hotter primary has been estimated from Stromgren photometry, and its age derived from reference to isochrones. This age is taken to apply to the secondary. Even in the case of F-type secondaries,...
Article
Rotation periods are reported for 14 main-sequence stars, bringing the total number of such stars with well determined rotation periods to 41. It is found that the mean level of their Ca II H and K emission (averaged over 15 years) is correlated with rotation period, as expected. However, there is a further dependence of the emission on spectral ty...
Article
Some results of monitoring the long-term chromospheric Ca II H and K emission variations in nearly 100 lower main-sequence stars at the Mt. Wilson 60arcsec telescope are summarized.
Article
Surface lithium abundance, a parameter which usually decreases with age in late-type stars, has been determined for Pleiades stars as cool as T(e) approximately 4700 K and Hyades stars as cool as T(e) approximately 5000 K. A large abundance spread is seen among the coolest Pleiades stars, consistent with their having been formed over an interval as...