At the Edge of NGC 891

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.

Benjamin J. Taylor, Michael D. Joner, and Scott B. Johnson
Cousins (1980) data for 54 of the standard stars of Neckel and Chini (1980) and published measurements are used to investigate the properties of the Neckel-Chini VRI system. For red stars, this system diverges from the Johnson (1962) system, despite frequent claims of identity between the two. The Neckel-Chini and Cousins systems, however, are closely comparable. Both of these conclusions were previously reached in a paper by Bessell (1983); fair to good quantitative agreement with his results are obtained. Reddening ratios, the scatter in the Neckel-Chini standard-star data, and the effect of this scatter on published measurements for program stars, are discussed. Transformations from the Neckel-Chini system to the Cousins system are given.
M. R. Perez and Michael D. Joner (et al.)

We have secured uvby β photometric data for 34 stars with previously determined spectral types in the fields of the young galactic clusters NGC 2244 and NGC 2264. Nearly a third of the sample stars are found to be nonmembers of the clusters based on photometric and astrometric indicators. Cluster color excesses, E(b-y), were found to be 0ṃ329±0.030 for NGC 2244 and 0ṃ031 ± 0.009 for NGC 2264. Indications of shell activity are detected for about 30% of the stars through β and c₁ index anomalies. Using the new theoretical calibration of uvby β indices by Lester, Gray, and Kurucz (1986), we estimated log g and Teff for the program stars. In addition, non-LTE models for Mihalas (1972) for early type stars and a calibration of Teff for stars (Philip and Newell 1975) were employed to improve the accuracies of the derived temperatures and gravities. Subsequent stellar radii, masses, and positions in the H-R diagram were calculated. Although most of the sample stars are on the main sequence, some show evidence of excess emission typical of pre-main-sequence objects such as Herbig Ae/Be stars and T Tauri stars. The cluster ages and the main-sequence lifetime for massive stars indicate that star formation in this region has not been restricted to a single epoch.

The authors compare their cluster (R-I) data (see the preceding paper) to measurements from other sources. For the Hyades, they find no case in which other data definitely agree with their own in both scale and zero point. For M67, affairs are better, and the authors can compile a merged (R-I) and (V-R) catalog for the evolved stars. These analyses yield one instance of disagreement between sets of Eggen R-I data, and two more in which such data disagree with measurements by others. A fourth example of this kind exists for the Hyades, and a fifth example exists for field stars. The combined evidence suggests that there have been recurring systematics in Eggen's (R-I) measurements.
The authors report new V magnitudes and/or (VRI)C colors for 17 Hyads and 11 bright M67 stars. They find that a source of variation in the Hyads (probably chromospheric variation) can change R-I while leaving V-R unaffected. The V magnitude can also vary, but is uncorrelated with R-I. The timescale for color variation is roughly a week; V magnitudes can vary on timescales from weeks to years.
Scott B. Johnson and Michael D. Joner
Observations of 314 stars with the uvbyß photometric system are used to establish the reddening in the direction of the nearby Triangulum galaxy M33. Color excesses are obtained for 151 A and F type stars in a 1° radius centered around the galaxy. A color excess of E(b-y) = 0.057 mag (E(B-V) = 0.077 mag) is obtained for a distance modulus m-M = 10. A secondary result of this investigation is the discovery of six suspected variable stars, as well as ten observations of V Triangulum, a β Lyrae eclipsing variable.