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
New photometric (uvby β) and spectrographic observations of the dwarf Cepheid BP Peg are described. A reddening value, E(b — y) = 0ṃ067, is derived from the photometry. Intrinsic (b — y), m₁ and c₁ values used in conjunction with a model-atmosphere grid yield a mean effective temperature, = 7470 K, a mean surface gravity, = 3.85, and [Fe/H] = -0.08. The pulsation theory and stellar model sequences yield Mbol = 1ṃ4, a mass = 1.85 𝕸⊙, and age of 1.3 × 10⁹ yrs. The radial-velocity data indicate a mean radial velocity of -30 km s⁻¹ and a total velocity range of 36 km s⁻¹.
Photometric (uvby β) observations ofthe prototype variable BL Her are described. The photometry indicates the variable is reddened. We have adopted E(b — y) = 0ṃ055. Intrinsic (b—y) and c₁ values are used to derive the mean temperature and surface gravity ‹T eff› = 6660 K, and ‹log g› = 2.46. The (m₁ =0.198 indicating the variable is very metal strong. We infer that [Fe/H] = + 0.20. An application of a modified Baade-Wesselink analysis to the photometric and radial-velocity data in the phase interval 0.45 ≤ φ ≤ 0.775, when most ofthe light variation can be attributed to a change in radius, yields (R) = 8.5 R⊙ and ‹Mv› = -0.5. The radius and surface gravity indicate that the mass is 𝕸 ≃ 0.75 𝕸⊙
We have used the new catalog of [Fe/H] determinations of Cayrel de Strobel et ai. (1985) to calibrate [Fe/H] in terms of δm₁. Three relations were found corresponding to F1-F5 stars, F5-F8 stars, and F8-G2 stars. Quadratic equations were found necessary to represent the data of the two early groups. Serious errors in [Fe/H] determinations of early metal-poor F stars can result if the previous linear calibrations are used.
The projected apparent rotational velocities of the dwarf Cepheids are v sin i ≤ 20 km s-1 for the variables for which spectrograms have been secured at dispersions ≤20 Å mm-1. The rotational velocities are very small compared with the typical rotational velocity of δ Scuti variables. The dwarf Cepheids are also restricted to a much more confined region in the H-R diagram than the δ Scuti variables. Unlike many typical δ Scuti variables, no dwarf Cepheids are found near the ZAMS.
New photometric (uvbyβ) and spectrographic observations of the dwarf Cepheid HD 94033 are described. The light amplitude, 0ṃ80 in V, and radial-velocity amplitude, 2K = 52 km s⁻¹, are unusually large. The mean effective temperature and surface gravity are ⟨Teff⟩ = 7650 K and (log g) = 4.14. The mean radial velocity, + 268 km s⁻¹, and low-metal abundance, [Fe/H] ~ -2.4, indicate that the star is a very extreme Population II star. Standard evolutionary theory indicates the mass is 0.9M ⊙ and the age is 6.5 × 1O₉ years. In many respects the star is similar to GD 428.
