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
Michael D. Joner, Benjamin J. Taylor, and C. David Laney (et al.)
New BV (RI)(C) measurements of Praesepe made at the South African Astronomical Observatory (SAAO) are presented. When those measurements are combined with those reported in previous papers in this series, it is found that they support previously determined V zero points for Praesepe, M67, and the Hyades. Support is also found for joint (V - R)(C) and (R - I)(C) zero points established previously for Praesepe and NGC 752. For the SAAO system of standard stars, a B - V correction to the Johnson system of about -9 mmag appears to be reasonably well established. The preferred (though not definitive) V correction is about +7 mmag. For the Landolt V system, zero-point identity with the Johnson system at a 2 sigma level of 4.8 mmag is found, and no color term as large as 4 mmag (mag)(-1) is detected. Updated CDS data files for Praesepe are briefly described.
New semicontinuous scans (with nearly contiguous passbands) are presented for alpha CMi and for 24 G and K giants. In addition, 12 such scans published in 1984 are reduced to an up-to-date standard-star system and adopted. The collected scans range from 3288 angstrom to at least 6940 angstrom, and they have been standardized to a system defined by alpha Lyr. They are supplemented by measurements of 23 of the program giants using six near-infrared passbands. Tests of the consistency and accuracy of the data yield encouraging results. The scans are used to test B and V response curves published by Bessell, and it is found that if those curves are weighted by wavelength (as Bessell proposes), they yield an acceptable wavelength baseline for B - V. The scans are also compared to a solar irradiance curve published by Lockwood et al. and standardized by measuring a Lyr. At wavelengths greater than 5248 angstrom, the Lockwood et al. curve appears to be "too blue," and a correction equation is proposed. However, that curve yields a satisfactory synthetic value of B - V and good agreement with a comparable stellar scan at wavelengths ranging from 4100 angstrom to 5207 angstrom.
New flux data are presented for nine nonvariable stars and 14 evolved variable stars with spectral types M and C. The data are from measurements of 21 passbands in the wavelength range from 7440 angstrom to 10834 angstrom, and they are comparable to measurements made by Wing some 40 years ago. Because the extinction algorithm applied to the new data is based partly on up-to-date calculations of telluric water-vapor effects, those calculations are tested for accuracy. In addition, methods used to calibrate standard stars both outside and inside the Paschen confluence are explained. After reddening corrections are applied to the flux data for the variable stars, those data are used to calculate color temperatures. In turn, those temperatures are used to derive blanketing corrections to color temperatures measured in the Wing filter system. Indices of absorption strength are calculated by comparing the flux data to blackbody colors derived from the color temperatures. It is found that the standard errors of those temperatures range from 3% to less than 1%. For the variable stars, the standard errors for the flux data range from 6.8 mmag to 11.6 mmag. For the nonvariable stars, the corresponding standard error is about 6.0 mmag.
Michael D. Joner, Benjamin J. Taylor, and C. David Laney (et al.)
New South African Astronomical Observatory (SAAO) BV(RI)(C) measurements of 19 Hyades stars and 11 M67 stars are reported. The zero points of the new color indices conform closely to those of SAAO data reported in a previous paper. In addition, the new M67 measurements of (V - R)(C) and (R - I)(C) are compared to data published previously by Taylor, Joner, and Jeffery. The results support conclusions drawn by those authors that the scale factors of their data are correct and that a scale factor problem exists in measurements published by Montgomery, Marshall, and Janes. The new values of B - V are used with Tycho data in tests of extant Hyades and M67 measurements and of the accuracy of the SAAO B - V system. A problem encountered previously with the Hyades B - V zero point is resolved, and an extant Hyades relation between B - V and (R - I)(C) is re-zeroed. A satisfactory zero point is also obtained for M67, and published photomultiplier values of B - V are reduced to that zero point, averaged, and tabulated. It is found that the zero point of B - V data published by Sandquist is satisfactory. However, tests of B - V measurements made by Montgomery et al. suggest that those data are not on a single zero point. Finally, the scale factor of the E region B - V system is found to be satisfactory, but a well-supported interim conclusion is drawn that E region values of B - V should be corrected by about - 9 mmag. It is suggested that this conclusion be tested by using instrumental systems that have not yet contributed to the testing process.
Using a protocol developed in previous papers in this series, the character of the Pleiades reddening is investigated. The protocol includes (1) analyses that yield results at the few-millimag level of precision and accuracy, (2) derivation of rigorous foundations for reddening values, (3) use of reddening techniques with limited metallicity sensitivity, (4) explicit zero-point control of input data, and (5) use of statistical analysis. It is found that in the eastern part of the Pleiades (as defined in a paper by Breger), E(B-V) = 34 +/- 11 mmag, with the quoted standard error depicting the amount of nonuniform reddening. In the western part of the Pleiades outside the "Southwest Nebula" (where E(B-V) > 0.2 mag), the mean value of E(B-V) = 57 +/- 5.8 mmag, and the intrinsic rms scatter in E(B-V) is 32 mmag. These results show that a widely adopted model in which E(B-V) = 0.04 mag everywhere in the Pleiades outside the Southwest Nebula is not correct for any extended region in the Pleiades. They also show that the photometric properties of brown dwarfs in the western part of the Pleiades are not yet well established. In a collateral analysis, published high-dispersion values of [Fe/H] are used to derive mean metallicities for the Pleiades and Praesepe. The resulting values of [Fe/H] are -0.039 +/- 0.014 dex and +0.057 +/- 0.022 dex, respectively. When these results are combined with a mean high-dispersion metallicity for the Hyades, it is found that they are strongly inconsistent with a published explanation for the Pleiades distance modulus problem that is based specifically on photometric metallicities.
New flux data are presented for 60 FGK stars on and near the main sequence. All the measurements are made at wavelengths suitable for temperature determinations. Measurements of all but seven program stars include four passbands in the Brackett continuum as well as 12 passbands in the Paschen continuum. After the accuracy of the new data is shown to be satisfactory, measurements of three "solar proxies" are compared to theoretical flux data from a solar model atmosphere calculated by Kurucz. In this case, agreement with rms scatter at the 5-7 mmag level is obtained. In addition, a possible zero-point problem with synthetic photometry of two Kurucz solar atmospheres is detected. Using measurements for 48 of the program stars and the Kurucz model grid, two sets of temperature data are then derived. The first set is based solely on data for the Paschen continuum, and the second set is derived from data for both the Paschen and Brackett continua. When the resulting temperatures are compared to temperature data on an angular-diameter scale, some data in the first data set yield offsets of about 40 K. However, no such offsets are found for the second data set. It is concluded that the Kurucz models yield correct continua between 6056 and 10404 angstrom for the program stars. In contrast, it appears that some of those models do not quite reproduce the line blocking in that wavelength range. The latter deduction is supported by analyzing flux data for a star (61 Cyg A) with relatively large amounts of line blocking. It is recommended that the measurements reported here be used again when further tests of theoretical flux curves for FGK stars are performed.