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Department Library

1996

John Morgan Powell (PhD Dissertation, August 1996, Advisor: Harold McNamara )

Abstract

New uvby-β-hk photometric observations of over 500 F- and G-type supergiant stars are reported. Special care to obtain accurate reductions of c1, the luminosity indicator for these stars, and m1, a metallicity indicator, are described. Whereas photometric reductions of ymag= Vmag, b-y, hk, and β for yellow supergiant’s can usually be merged with non-supergiant’s without significant error, m1 and especially c1 require special treatment. A new reddening calibration for yellow supergiants is reported using [m1] corrected for metallicity as the temperature indicator. Using b-y, c1, and hk, values for temperature, surface gravity, and metallicity have been estimated from the new Kurucz model atmospheres.The inferred temperatures appear to be reasonable but the surface gravitates needed to be corrected and the metallicities need further improvement. Since the Kurucz models predict values of log g which imply absolute magnitudes which are too faint in our galaxy as well as in the Large and Small Magellanic clouds, a correction in terms of log g has been applied to the derived values of MV. The metallicity values derived here imply a difference in [Fe/H] between the Small Magellanic Cloud and the Large Magellanic Cloud of about 0.3 dex, in rough agreement with spectroscopic studies. However, to our surprise the results do not indicate the expected difference in [Fe/H] between the Large Magellanic Cloud and the Milky Way Galaxy (found spectroscopically to be about 0.3 dex). This may be due to microturbulence differences between supergiant stars in our galaxy as compared to those in the Magellanic Clouds. Yellow supergiant stars in this study do not clearly delineate galactic spiral arm structure as one would expect. Errors in their distances are probably the dominant cause, but random motions will also cause them to leave their spiral arm birthplaces. An attempt to derive an improved galactic metallicity gradient for yellow supergiant stars was unsuccessful due in part to the wide variation in metallicity among the program stars.

1989

John Morgan Powell (Masters Thesis, December 1989, Advisor: Harold McNamara )

Abstract

New VRIC and uvby-beta photometric observations of the large amplitude DSCT variable V567 Ophiuchi are reported. An improved period (0d.149523650 +/- 0d.000000043) was found. Large errors (11 minutes) in the calculated ties of maximum light, O-C, and variations in the amplitude (0m.03) and width of the light curve suggest the star has a secondary overtone mode of pulsation. An E(b-y) = 0m.285 +/- 0m.004 was determined using the Crawford A and F star calibrations. The most recent Kurucz model atmosphere calibrations indicate (Teff) = 7430 +/- 80 K and (log g) = 3.74 +/- 0.13. Results of the m1 analysis yield [Fe/H] = -0.2 +/- 0.2 which implies V567 Ophiuchi has approximately solar metal abundance. A value for the radius 3.3 +/- 0.3 Rʘ was determined by the surface brightness method and checked by the Baade-Wesselink method. Values for the absolute magnitude MV = +1m.1 +/- 0m.2, distance 610 +/- 60 pc and mass 2.1 +/- 0.7 Mʘ were also derived. Varying values for the systematic velocity gamma (-48, -28, and -15 km/sec) and large timing errors, O-C, suggest the star may be a binary star system. Perhaps the star has both orbital motion and a secondary mode of oscillation.

1987

Aaron L Alexander (Masters Thesis, April 1987, Advisor: Harold McNamara )

Abstract

Photometric (uvbyβ) observations of the prototype variable BL Her are described. The photometry indicates the variable is reddened. We have adopted E (b-y) = 0.m055. Intrinsic (b-y) and c1 values are used to derive the mean temperature and surface gravity (Teff) = 6660° K, and (log g) = 2.46. The (m1)0 =0.198, indicating the variable is very metal strong. We infer that (Fe/H) = +0.26. An application of a modified Baade-Wesselink analysis to the photometric and radial-velocity data in the phase interval 0.45 ≤ ᴓ ≤ 0.775, when most of the light variation can be attributed to a change in radius, yields (R) =8.5Rʘ and (Mv) = -0.5. The radius and surface gravity indicate that the mass is M≈0.75Mʘ.

1984

Chulhee Kim (PhD Dissertation, August 1984, Advisor: Harold McNamara )

Abstract

"Color excesses of 446 classical cepheids have been taken from literature and transformed to a single homogenous system. On the basis of these color excess data, fundamental data for 401 classical cepheids have been compiled and a discussion of galactic structure based on their space n distribution of long-period cepheids on the projected Galactic plane and the position of these spiral features have been compared with those from other optical racers such as HII regions and OB star groups. The z-coordinate distribution of cepheids confirms the finding of Fernie (198b

1982

Clifton D Laney (PhD Dissertation, December 1982, Advisor: Harold McNamara )

Abstract

Accurate MK spectral types have been obtained for 58 Cepheids in the Galaxy and the Magellanic Clouds from 121 spectrograms. Simultaneous uvbyβ photometry has been obtained with many of the spectrograms. The spectra of galactic and LMC Cepheids are found to be very similar, and Cepheids in both systems appear to obey the same (B-V)o vs. spectral type relation. The low E (B-V) values of Feltz and McNamara (1980) and certain other recent authors are confirmed. The spectra of SMC Cepheids show slightly weaker metal lines, and SMC Cepheids average about 1.3 subclasses earlier in spectral type than LMC and galactic Cepheids at the same value of (B-V)o. Spectral types of LMC and SMC Cepheids at minimum light are found to be later than those reported by Feast (1974) when luminosity effects are allowed for. Curves of growth have been constructed for 7 SMC Cepheids, 5 LMC Cepheids, and 13 Milky Way Cepheids and spectral standards. Comparison indicates that (Fe/H)LMC = -0.06 ± 0.10 and (Fe/H)SMC = -0.50 ± 0.08.

1981

Michael DeLoss Joner (Masters Thesis, August 1981, Advisor: Harold McNamara )

Abstract

New BVR and uvby observations of XX Cygni are reported. An improved period (P=0.134865070) was found for XX Cygni. An E(b-y) = 0.058 magnitude was determined from the Crawford calibrations. Model atmosphere calibrations indicate <Teff > = 7530K and <lo g> = 3.66. a radius of 2.6 R has been determined for XX Cygni. The values M=1.1M and <Mbol> = +1.5 were also determined in his report. Radial velocity and proper motion values indicate XX Cygni is a high-velocity star. Finally, the results of the m1 analysis yield [Fe/H] = -0.49 which shows XX Cygni to be a metal-poor star

1977

Kent A Feltz (PhD Dissertation, January 1977, Advisor: Harold McNamara )

Abstract

The uvbyβ and khg photometric systems have been employed to acquire data on 162 field stars in the proximity of 18 bright cepheids. Color excesses of twelve of these cepheids have been obtained from the field star data. The reddening gradient at the position of δ Cep is found to be about 0ṃ05 per 100 parsecs in E(b-y); the gradient in the other fields is apparently less than 0ṃ005 per 100 parsecs. A comparison of the color excesses with previously published results is given. Four cepheids: Rt Aur, ET Cyg, ζ Gem, and T Vul have relatively small and well-established reddening values; these values are systematically smaller tha those obtained by others. These four stars, together with α UMi, can serve as standards to calibrate reddening-free indices with intrinsic color indices such as (b-y)o or (B-V)o.

1976

Karen A Halberg Young (Masters Thesis, April 1976, Advisor: Harold McNamara )

Abstract

New uvbybeta photometry of DY Pegasi is reported as well as calcium K-line measurments for DY Peg, DY Her, Eh Lib, and YZ Boo. An improved period has been found for DY Peg. An average surface temperature of 7800K, and log g value of 4.0 have also been derived. Radial velocity measurements of DY Peg give a variation in Vr of -37 to +2 km/sec, with a mean value of -18 km/sec. A phase lag between the radial velocity and the light curve of 0.05 +/- 0.02 was found. Wesselink’s method yields a radius of 1.3 R® which suggests a low mass of 0.6 M®, and an Mbol = ®2.9. A K-index was formed from CaK line measurements and calibrated to Henry’s K-index. A beta-index was formed from the Hbeta line and was used to remove the temperature dependence from the K-index. Dy Peg and YZ Boo were found to be metal poor; EH Lib slightly metal poor; and DY Her was found to be metal strong.

1975

Wilbur Reed Langford (PhD Dissertation, December 1975, Advisor: Harold McNamara )

Abstract

Intermediate-band photometric observations of nine dwarf cepheids and two RR Lyrae stars have been obtained in the uvby photometric system. Intrinsic color indices, temperatures, gravities, absolute magnitudes, masses, and a chemical composition indicator are derived from the photometry with the aid of the c1, b – y, and m1 indices. The results of the investigation indicate (1) the dwarf cepheids exhibit a large range in metal abundance, (2) the metal-poor stars are high-velocity objects exhibiting the shortest periods of pulsation, (3) the variables fall in the instability strip in the H-R diagram and exhibit a period-temperature relation, (4) the dwarf cepheids obey a period-luminosity relation (Mv ~3.5 to Mv ~0.8) with the stars of longest period being the most luminous, (5) the metal-strong variables have masses of ~2 Mʘ which the metal-poor variables appear to have masses less than one solar mass, (6) the variables are found in both stellar populations and appear to be in a post-main-sequence stage of evolution.

1973

Roger D. Tippets (Masters Thesis, August 1973, Advisor: Harold McNamara )

Abstract

Forty-eight visual binaries with secondaries of spectral types AO-GO have been observed in the uvbyβ photometric system. Absolute magnitudes of the stars Mv to Δc1. Evolutionary theory predicts all secondaries observed in this sample should like ≤0ṃ5 above the ZAMS. Our results show that 35% of the secondaries have evolved more than 0ṃ6 above the ZAMS contrary to expectation. The assumption that all secondary components of visual binaries with large separations in apparent magnitudes are ZAMS stars in shown to be invalid. The time scales of evolutionary theory may be in error but it is possible this discrepancy may be due to the existence of a zero-age band instead of a line.

1968

John Smith Beardall (Masters Thesis, January 1968, Advisor: Harold McNamara )

Abstract

The KHG photometric index is defined. Measurements were made using the KHG index for 230 stars in the Hyades cluster, the Coma Berenices cluster, and the stellar field for which B-V and b-y color indices are known. The KHG index was shown to be independent of atmospheric extinction. It was also found to have higher resolution than B-V or b-y. The index was used to predict metal abundance with higher precision than the m1 index confirming that the stars in the Coma Berenices cluster are metal deficient relative to the Hyades stars. The presence of a stronger K line emission feature in the Hyades stars was confirmed.

Stephen Llew Jr Johnson (Masters Thesis, May 1968, Advisor: Harold McNamara )

Abstract

Photoelectric measurements of fifteen globular star clusters have been secured in the c1, b-y, m1, and β photometric systems and in narrow-band photometric systems that measure the strength of the G band, Hγ line, and the (Mg) b lines. The photoelectric observations have been utilized to classify the clusters, and obtain reddening and metal abundance data. With some exceptions the b-y values are found to be approximately the same for all the clusters. The m1 and c1 indices are found to correlate very well with the number of blue and red horizontal branch stars in each cluster. The metal abundances derived from the cluster m1 values and the Hyades m1 values indicate a range of the logarithm of the ratio of iron to hydrogen relative to the sun from -2.15 for extremely metal poor clusters to -0.05 for clusters with near to normal metal content. The metal abundances derived from the (Mb) b line strength indicate a range of the logarithm of the number of Mg atoms relative to normal field stars from -0.88 for extremely metal poor clusters to -0.38 for clusters with near to normal metal content.

Helen Claire Sievers (Masters Thesis, May 1968, Advisor: Harold McNamara )

Abstract

An abundance analysis was made of the B3 V star HD 37058 using Wrubel’s curve of growth. The two striking results of the study are that titanium is overabundant by a factor of about 220 and strontium by 17000. These anomalies together with the presence of a strong magnetic field suggest that the star is a B type counterpart of the peculiar A stars.

1966

James H. Karle (Masters Thesis, January 1966, Advisor: Harold McNamara )

Abstract

Photometric measurements employing narrow-band interference filters have been made for 13 visual binaries and for a number of stars in the galactic cluster Messier 39. c and l indices are determined with the probable error for a single observation of ±0ṃ01 in the c parameter and ±0ṃ006 in the 1 parameter. There is good agreement in the (B-V) color indices and absolute magnitudes determined from the c and l indices with those given by Johnson (1953). An analysis of the absolute magnitudes derived from these indices show that a number of the binary components are brighter than main sequence stars of the same spectral class. The same differences that exist between the absolute magnitudes and color indices determined from the c-l photometry and those of Johnson are systematic and a discussion is made of the errors. Absolute magnitudes of the visual binaries are also determined from the c1 index. These magnitudes indicate that the ∆MV/∆c1 factor used to determine the absolute magnitude of a star in terms of Stromgren’s relation between (B-V) color index and MV of a star on the “zero-age main sequence” is probably too small. Absolute magnitudes of stars in the cluster Messier 39 have also been attained from c-l photometry and the c1- (B-V) indices. The absolute magnitudes from the c1- (B-V) values appear to be superior to those given by the c-l indices. A distance modulus of the cluster of 7ṃ3 corresponding to a distance of 288 parsecs is found from the absolute magnitudes derived from the c1- (B-V) indices of the 14 cluster stars.

1965

Ellis D., Jr. Miner (PhD Dissertation, January 1965, Advisor: Harold McNamara )

Abstract

Photometric measurements utilizing narrow-band interference filters have been made for 105 F5-K5 stars brighter than apparent magnitude 7ṃ0. The spectral features measured were the G-band, the CN-band at 4200 A, and a metallic abundance index, m’. The resulting spectral indices were calibrated against the B-V colors and visual absolute magnitudes using stars with well-determined colors and accurate trigonometric or cluster parallaxes. B-V colors and absolute magnitudes are predicted with probable errors of ±0ṃ4, respectively. The results have been applied to the measurement of 25 members of eclipsing binary systems, 17 of which are fainter components of their respective systems. 16 of the 17 fainter components were found to exhibit moderate to extreme deficiencies in their metal-to-hydrogen ratios relative to solar abundances. For the Hyades and Praesepe giants the G-band is found to be somewhat weak relative to field stars of the same color and magnitude. CN anomalies not reflected by corresponding anomalies in the G-band give rise to errors in the predicted MV values, but for most stars, this effect is considered small. Further complications in MV predictions arise for stars with high rotational velocities.

1962

George E Matthews (Masters Thesis, May 1962, Advisor: Harold McNamara )

Abstract

(U-B)0 colors and beta values for thirteen Beta Canis Majoris stars observable from the Northern Hemisphere were obtained with the aid of photoelectric photometry using narrow band interference filters. The results derived in this paper were compared with results obtained by other observers and a definitive set of colors and beta values were established within the limits of the data. The beta quantity was correlated with absolute magnitude using the three galactic clusters M36, NGC 2362 and h and x Persei. The stars in h and x Persei were found to be much lower in luminosity for a given spectral type than was previously thought. Absolute magnitudes were derived for the Beta Canis Majoris stars using the above correlation. These magnitudes proved no more accurate than magnitudes found previously. Therefore, mean magnitudes were calculated and an estimated range was set on these mean magnitudes. The existence of a period-luminosity relationship for the Beta Canis Majoris stars was reaffirmed but the exact form was found to be still in doubt. The pulsation constant, Q, was calculated for this group of stars and the result was .016. Finally, the Beta Canis Majoris stars were plotted in an H-R diagram. They were found to be one magnitude above the “zero age” main sequence as defined by Johnson.

1961

Gordon C Augason (Masters Thesis, August 1961, Advisor: Harold McNamara )

Abstract

Wilford Bruce Hilton (Masters Thesis, June 1961, Advisor: Harold McNamara )

Abstract

Observations consisting of 39 spectrograms obtained with the 100-inch telescope at the Mount Wilson Observatory were analyzed for radial velocities. Analysis of line-profile changes in the Ca K line indicate that some absorption takes place in a gaseous ring associated with the primary star. Hα emission is detected throughout the cycle, and measurement of the Doppler shift of the emission gives a velocity of about 208 km/sec for the emitting ring around the primary star. A consistent velocity-curve was obtained for the secondary star, and this curve together with a free-hand velocity-curve drawn for the primary star gives the orbital elements: K2 = 111.0 km/sec, K1 ≅ 17.5 km/sec, γ = -11.0 km/sec, a2 sin i = 1.6 x 107 km, a1 = sin I ≅ 2.6 x 106 km, m1/m2 ≅ 6.3, m2 sin3i = 0.32⨀, and m1 sin3i ≅ 2.0⨀. The range, 2K, of 220 km/sec of the observed velocity-curve of the secondary star is more than twice that determined in previous radial velocity investigations. Measurements were made with a photoelectric photometer attached to the 24-inch reflecting telescope of Brigham Young University in both broad-band and narrow-band three-color photometry. Line strength measurements were also made using interference filters. That the primary eclipse was found to be partial is in striking contrast with the results previously determined by photographic and spectrographic methods. The period was corrected slightly to 10.622543 days. The narrow-band photometry results indicate that the secondary component is an F5 IV subgiant with an absolute magnitude Mv = +2.6, and an abnormally weak Ca K line. The anomaly of this line is also evident in the spectrograms. The A star narrow-band measurements are more uncertain but indicate that the spectral type of the primary star is probably between A3-A5 with an absolute magnitude Mv ≅ +1.5.

1960

Loren R Anderson (Masters Thesis, June 1960, Advisor: Harold McNamara )

Abstract

A photometer was designed and built to be attached at the Cassegrain focus of the 24-inch telescope at Brigham Young University. The optical train consists of a flip-flop mirror which diverts the beam of a finding eyepiece, a diaphragm slide, a flip-flop mirror for the setting eyepiece, a shutter, a filter slide with provision for seven filters, a Fabry lens and photocell. The dynode voltage for the 1P21 photomultiplier tube is supplied by a battery source. The signal from the photomultiplier tube is sent to a d-c amplifier and the results are displayed on a Brown Strip Chart Recorder. Photometric test observations were made to determine atmosphere extinction, and a linear relation was obtained which gave an extinction coefficient of -0ṃ25, which is in agreement with other observers for stars of similar spectral type. The short-period variable star AD CMi was observed on three nights. The variation through the blue and yellow filters, and the other variation (B-V), were in agreement with previous observations made on this star except for a slight period correction. With the correction, the Heliocentric maximum occurs at JD 2436 601.8228 + 0ḍ122974E. Color observations were also obtained on 20 stars. The colors were plotted with corresponding B-V values obtained by H.L. Johnson. A liner relation was obtained with a slope of 1.51, indicating that the wavelength separation of the blue and yellow filters used for the observations did not correspond to the B, V system used by Johnson. The average deviation of the observation from a straight line was 0.023 magnitudes. From the observations, the response of the photometer appears to be linear. From the deflection of the faintest star measured (about 10th magnitude), the limiting magnitude appears to be about 12.5. The photometer is capable of determining magnitudes and performing color photometry with a mean error of ± 0.02 magnitudes.

1959

H Kimball Hansen (Masters Thesis, January 1959, Advisor: Harold McNamara )

Abstract

Observations consisting of 72 spectrograms obtained with the 100-inch telescope at Mt. Wilson Observatory were analyzed for radial velocities, equivalent widths, and line-profiles. Analysis of line-profile changes in the He lines and measurements of changes in the central intensities of the H lines reveal that considerable absorption takes place in gas streams which surround the system. Measurements of the amount that the cores of the He lines are shifted make possible a corrected velocity-curve, and this corrected curve gives the orbital elements K = 36.5 km/sec, γ = -14.5 km/sec, a sine I = 7,620,000 km, and f(m) = 0.0766⨀. The range of the observed velocity-curve is less for the H∝ line than for the average of the H lines or for the He lines. Doubling of the H lines is observed during eclipse. The range of the rotational disturbance is 325 km/sec. Rotational velocity measurements made from the profiles of four different He lines indicate that there is differential rotation in the atmosphere of the B2 star, with the smaller rotational velocities being observed at higher levels. The maximum rotational velocity (V sine i) measured by this method is 250 km/sec. The intensities of the Hγ and Hδ lines correspond to a bolometric magnitude of -5.0. Computing the masses by assuming the primary star to be on the main sequence results in dimensions for the secondary star that put it beyond its Roche limit. Similar computations from the assumption that the secondary star just fills this limit result in a very small mass for the primary star. Comparison of the contradictions involved in the two results gives some insight into the probable masses of the components of the system. Rotational break-up considerations indicate that the mass of the primary star is probably greater than 2.0⨀. A schematic model of the gas streams which surround the system is developed from the observations. The spectrum of the secondary star was not detected.

1958

Kay Baker (Masters Thesis, June 1958, Advisor: Harold McNamara )

Abstract

"The total absorptions of the Hδ and Hγ lines were measured in the spectra of 33 stars of the star clusters NGC 2362 and M 36 ranging in spectral type from B1 to B9. These stars were used as standards of absolute magnitudes to establish relations between the intensities of the Hδ and Hγ absorption lines and the absolute magnitudes of the B-type stars. The relations were found to be

1957

Duane R. Aston (Masters Thesis, January 1957, Advisor: Harold McNamara )

Abstract

A study of U Cephei has been made from 106 spectrograms taken at Mt. Wilson Observatory. Of these, 46 spectrograms have been taken in the red region of the spectrum. An attempt has been made to find asymmetries in the various component lines of the star. No observable asymmetries have been found. The only noticeable peculiarities observed were those found in the H∝ lines. Differences in central intensity were found for phases of 0.2 and 0.7 days. Those at 0.2 days were of greater intensity than those at 0.7 days. The H∝ line may be the key to the peculiar behavior of U Cephei. Peculiar behavior of all star lines was noted around phase 0.7 days. A study of the various component velocities show that each of the star lines lead to somewhat different velocity curves. For this reason, c cos w is not zero by the spectrographic methods.