Graduate Student Savanah Turner Publishes Study of over 300 L and T dwarfs

BYU Astronomy Research Group Joins the Astrophysical Research Consortium (ARC)

As of January 2021 BYU will be a member of the ARC Consortium (Link to Consortium) with access to the ARC 3.5-m telescope and the 0.5-m ARCSAT telescope.  The primary use of the ARC 3.5-m telescope time is for graduate student projects.  This provides a wide array of instrumentation that is currently being used to study objects in the solar system all the way to studies of the large scale structure of the Universe.

Other BYU Astronomy Facilities

In addition to our telescope time from the ARC consortium, we operate a number of our own astronomical facilities

West Mountain Observatory (West Mountain)

This is our mountain observatory at about 6600 ft above sea level.  This consists of three telescopes: 0.9-m, 0.5-m, and a 0.32-m. It is a 40 minute drive that ends in a 5 miles drive up a dirt road. The mountain itself can be seen from campus. We don't provide any tours of this facility.

Orson Pratt Observatory

The Orson Pratt Observatory is named for an early apostle of the Church of Jesus Christ of Latter-Day Saints.  It is our campus telescope facility and contains a wide variety of telescopes for student research and public outreach. We operate a 24" PlaneWave telescope in the main campus dome, plus a 16", two 12", one 8", and a 6" telescope on our observation deck.  The telescopes are all fully robotic. Beyond this we have a large sections of telescopes used on public nights.

Royden G. Derrick Planetarium (Planetarium)

This is a 119 seat, 39" dome planetarium with acoustically treated walls to allow it's use as a lecture room. Recently we upgraded to an E&S Digistar7 operating system with 4K projectors.  The planetarium is used for teaching classes, public outreach, and astronomy education research projects.





Selected Publications

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Cousins vri photometry of the hyades, coma, and m67
For little-evolved stars in the Hyades, Coma, and M67, Cousins VRI photometry which includes and expands on results published in other systems by Taylor is presented. Observing and reduction procedures and error analysis are discussed in some detail, and evidence is presented that the transformations to the Cousins system are satisfactory and the results are internally consistent. Comparisons with data published by Mendoza yield agreement in R-I and V-R for the Hyades and V-R for M67. Disagreement is found, however, in both color indices for Coma and in R-I for M67, and reasons are suggested for favoring the obtained results in these cases. By comparing Mendoza's M67 K-giant data with those of other observers, it is found that any problem with Mendoza's M67 results is apparently limited to the faintest stars he observed. A suggestion by Schild and Weeks that Mendoza's M67 R magnitudes are about 0.1 mag in error is also tested, and it is found that available evidence does not support this suggestion.
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Photometric properties of HD 200925
Michael D. Joner and Scott B. Johnson

Photometry of HD 200925 in the uvby and β systems has been secured and analyzed. The data strongly indicate that the variable is multiperiodic. A reddening value, E(b—y) = 0ṃ040, has been derived from the variable-and comparisonstar observations. Analysis of the intrinsic (b—y) and c x values for one primary pulsation cycle are used to determine a mean effective temperature (Teff) = 7470 K, and a mean surface gravity (log g) = 3.87. HD 200925 is found to have a somewhat higher abundance, [Fe/H] = +0.33, than stars in the Hyades. These values do not conform to the presently accepted properties for dwarf Cepheid variables.

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Modernizing an Older Telescope
Michael D. Joner and David P. Phillips
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A photometric and spectrographic study of YZ Bootis

Photometric observations of YZ Boo in the uvby beta system obtained in summer, 1982, with the two-channel sky-compensating photometer on the 61-cm reflecting telescope at West Mountain Observatory are reported. The period is calculated from both the present and published light maxima as 0.104091593 days. The phase variation of the different photometric parameters is given in tables and graphs. A reddening value E(b-y) = 0.018 m is found, and further parameters are estimated, using the model atmospheric grid of Breger (1977) in some cases: T(eff) = 7590 K, log g = 3.95, Fe/H = -0.025, M(bol) = 1.7, mean radial velocity = -20 km/sec, and total velocity range = 35 km/sec. An attempted Wesselink radius calculation was unsuccessful. YZ Boo is classified as a normal dwarf cepheid of Population I.

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The Nature of the Dwarf Cepheid XX Cygni

Photometry of XX Cyg in the uvby and β systems has been secured and analyzed. A reddening value, E(b—y) = + 0ṃ057, is derived from the photometry. Intrinsic (b —y) and c₁ values are used to determine a mean effective temperature, ⟨Teff⟩ = 7530 K, and a mean surface gravity, ⟨log g⟩ = 3.66. XX Cyg is found to be a metal-poor dwarf cepheid with [Fe/H] = -0.49. A radius of 2.4 R⊙ has been found from the Wesselink method. The radius and effective temperature indicate that ⟨Mbol⟩ = + 1.7. A mass of 1.0𝕸⊙ is found from the radius and effective gravity. The radial-velocity data yield a mean radial velocity of -108 km s⁻¹ and a total velocity range of 37 km s⁻¹.

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Measurement of solar wind electron density and temperature in the shocked region of Venus and the density and temperature of photoelectrons within the ionosphere of Venus
Presented herein are measurements of the solar wind electron number density and temperature near and within the bow shock of Venus. The measurements were made by the Pioneer Venus mission Orbiter Retarding Potential Analyzer operating in its suprathermal electron mode. The measurements are essentially point measurements. The spacecraft travels approximately 0.8 km during the 0.1 s time interval required to record a single I-V curve. The dual measurement of a density and temperature is obtained from one sweep by least squares fitting a mathematical Maxwellian expression to the I-V curve. The distance between successive measurements is approximately 100 km. In many orbits, when the spacecraft is crossing or traveling within the bow shock, the derived densities and temperatures (high density, high temperature (HDHT)) are large, densities of the order of 100 cm−3 and temperatures of the order of several hundred eV. We interpret these HDHT measurements as measurements in regions where the large, directed kinetic energy of the solar wind ions is being degraded into randomized, more thermal-like energy distributions of the electrons and ions through wave-particle interactions. The HDHT values define the electron energy distribution in the limited energy interval 0 to 50 eV. We assume that the underlying electron flux distributions are flat topped like those measured in the Earth's bow shock. We also report densities and temperatures of EUV produced photoelectron energy distributions measured within the ionosphere.