Utah Aurora - May 10/11 2024

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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Period-luminosity relations of sx phoenicis stars
We propose the following criteria to distinquish between fundamental (F) and first-overtone (H) pulsating SX Phoenicis variables: the (H) pulsators are SX Phe stars with nearly symmetrical light curves and light amplitudes (total range) less than or equal to 0.29 m in V; the (F) pulsating stars have light amplitudes greater than or equal 0.25 m in V and asymmetrical light curves. These criteria provide a separation of the stars into two groups that lead to two parallel P - L relations that are offset by 0.37m. This offset is in excellent agreement with the offset, 0.36m predicted from the double-mode pulsating variable SX Phe. The (H) pulsating variables have shorter periods on average than the (F) pulsators as predicted by P1/ P0 = Q1/ Q0 approximately equal 0.778. The mean periods of the SX Phe stars in globular clusters are shown to be correlated with the metallicity (Fe/H) in the sense that the shortest period variables are found in the most metal-poor clusters. The fundamental-mode SX Phe stars in the Carina dwarf galaxy give a distance modulus of 20.0 and (Fe/H) = -1.5.
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Long-Term Period Variations of the SX Phoenicis Star CY Aquarii
John M. Powell, Michael D. Joner, and D. H. McNamara

New photoelectric times of maximum light of the SX Phoenicis variable CY Aquarii are combined with times of maximum light extending over 64 years to determine the long-term period variations. The recent data do not show significant cycle-to-cycle variations as some have reported but the data do clearly show an abrupt period change in 1989 corresponding to a new period of 0.(d)061038612.

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A Photometric Study of XX Virginis and V716 Ophiuchi
D. H. McNamara and M. D. Pyne
We present Stromgren photometry of the two Population II variables XX Virginis and V716 Ophiuchi. An analysis of the photometry, yields the following physical parameters of the variables: for XX Vir [T(eff)] = 6410 K, [Fe/H] = -2.0, and [log g] = 1.95; for V716 Oph [T(eff)] = 6450 K, [Fe/H] = -2.1, and [log g] = 1.67. The [log g] values of these two metal-poor variables are considerably smaller than for the metal-strong variable BL Herculis ([log g] = 2.37). The big surprise in this investigation is that the surface gravity of V716 Oph (P = 1.12d), the shorter-period variable, is smaller than the surface gravity of XX Vir (P = 1.35d), the longer-period variable. With the aid of the P square-root rho = Q relation we derive a semitheoretical P-L relation for the Type II Cepheids of the form M(nu) = -1.88 log P + 0.13. This expression is in rough agreement (within the uncertainties of many quantities used in deriving the expression) with the observational data. The relatively gentle slope of the P-L relation (compared with the slope of the P-L relations of other pulsating stars) is probably a consequence of the fact that the masses of the Type II Cepheids are constant or nearly constant, independent of period, and a large variation of their M/R values with period.
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A photometric and spectrographic study of sx phoenicis
Simultaneous photometric (uvbybeta) and spectrographic observations of SX Phe are described. Analysis of the light and velocity frequency spectra are performed. It is shown that all frequencies detected are harmonics or combinations of the fundamental and first harmonic frequencies. Intrinsic (b-y) and c1 values used in conjunction with a model-atmosphere grid appropriate for a star with [M/H] = - 1.0 yields [T(eff)] = 7630 K and [log g] = 3.90. Standard evolutionary models indicate the mass is 1.13 M. and [M(v)] value is + 2.9. The radial-velocity data indicate a mean radial velocity of - 37 km/s and a total range of 38 km/s.
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A photometric and spectroscopic study of v567-ophiuchi

New uvbyß photometric observations of the dwarf Cepheid V567 Oph are reported. An improved period (0ḍ49523641 ± 0ḍ000000043) is found. Large errors in the calculated times of maximum light (O — C ≈7 minutes), variations in the light amplitude (δΔV≈0ṃ03), variations in the width of the light curve (δΔΦ≈ 0.1 cycle FWHM), and differences in the radial-velocity amplitude (2K = 35 ± 4, 26 ± 2, and 30 ± 7 km sec⁻¹ ) suggest the star has a secondary overtone mode of pulsation. An E(b -y) = 0ṃ285 ± 0ṃ004 indicates the star is heavily reddened. The most recent Kurucz model-atmosphere calibrations indicate ‹Teffŕ = 7430 ± 80 and ⟨log g⟩ = 3.74 ± 0.13. [Fe/H] = — 0.2 ± 0.2 implies V567 Oph has approximately solar metal abundance. Attempts to employ the surface brightness and Baade-Wesselink methods to determine the radius of the star give inconclusive results. A period, radius relation for dwarf Cepheids indicates a radius of 3.2 ± 0.2 R⊙ . The data indicate that the absolute magnitude is M v = + 1ṃ1 ± 0ṃ1, the distance is 620 ± 30 pc, and the mass is 1.85 ± 0.2𝕸⊙

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A photometric and spectrographic study of BP Pegasi

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.