The Tulip in the Swan

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

We analyze photometric observations of high-amplitude delta Scuti stars (HADS) in the globular cluster omega Cen and the Carina galaxy. The pulsation modes of the HADS are inferred primarily from their positions in V, log P diagrams. For omega Cen we identify nine fundamental pulsators (F), 22 first-overtone (1, O), one second-overtone (2, O), and probably two third-overtone (3, O) stars. The majority of the F pulsators have light amplitudes Delta V greater than or equal to 0.15 mag, but two have Delta V < 0.15 mag. Four of the 1, O pulsators have Delta V > 0.15 mag, but the majority have smaller amplitudes. We find that the F pulsators tend to have more asymmetric light curves. The Carina variables are all large-amplitude variables. Fourteen are F pulsators and six are 1, O pulsators. At least one and possibly two 1, O stars appear to have asymmetric light curves unlike those found in omega Cen. The data are very uncertain, so the asymmetry may be an artifact of observational uncertainty. The HADS data along with their P-L relation are utilized to find the distances to omega Cen and the Carina galaxy and absolute magnitudes of their horizontal branches (HB) or RR Lyrae stars. We find the distances to be d = 6370 pc to omega Cen and d = 124,000 pc to the Carina galaxy. The M-v(RR)-values for the omega Cen RR Lyrae stars are M-v(RR) = 0.14 (Oost II variables) and M-v(RR) = 0.28 (Oost I stars); M-v(HB) = 0.29 for the Carina galaxy.
D. H. McNamara, J. B. Madsen, J. Barnes, and B. F. Ericksen
The Optical Gravitational Lensing Experiment (OGLE) data on high-amplitude delta Scuti stars (HADS) and RR Lyrae stars have been analyzed to determine the distance to the Galactic bulge. Individual color excesses and V absorption for each individual variable star have been computed, which lead to accurate [V-0] magnitudes. The period-luminosity relation of the HADS is utilized to calculate distance moduli. We find that the metal-strong HADS are concentrated strongly to the bulge. The best distance modulus to the bulge from the HADS data is 14.49 +/- 0.06 mag. The dependence of M-v on period for the bulge RR Lyrae stars can be found from the reddening-free magnitude TV-I. The zero point of the M-v-log P relation is set with the horizontal branches of Oosterhoff type I globular clusters. M-v congruent to 0.44 mag (long-distance scale) in the log P interval -0.29 to -0.22 as inferred by main-sequence fitting of the clusters to local subdwarfs and utilizing short-period HADS in the clusters. The best distance modulus to the bulge from the RR Lyrae (ab) stars is 14.45 mag, which compares favorably with the distance modulus of 14.49 mag found from the MADS. We adopt the mean value 14.47 +/- 0.08 mag for the bulge distance modulus. A small additive correction leads to 7.9 +/- 0.3 kpc as the best distance to the Galactic center.
D. H. McNamara, J. B. Madsen, J. Barnes, and B. F. Erickson
We discuss the slope of the RR Lyrae variables M-v,[Fe/H] relation by two independent methods. We show that the slope is 0.32 if Baade-Wesselink M-v values are used only for stars with [Fe/H] > - 1.5. Because the metal abundances of the variables are constant or nearly so for a large range of periods (the Oosterhoff I variables with log P values in the range -0.29 to -0.215), a flat section in the M-v,[Fe/H] relation is produced that tends to reduce the slope if stars with log [Fe/H] < - 1.5 are included in the solution. An analysis of data on RR Lyrae stars in the Galactic bulge yields a slope of similar to 0.31.