Graduate Student Savanah Turner Publishes Study of over 300 L and T dwarfs

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 have compared the Hyades, Coma, and a set of field standard stars in the V and Stromgren-beta systems. If Stromgren data by Crawford and his collaborators are considered, all the data turn out to be on the same system; no corrections as large as several mmag are required to achieve this state. For beta, similar consistency between the Hyades and Coma is already known to exist. We find that for the standard stars, beta values from the literature are consistent with the Hyades-Coma system. For V, we adopt corrections derived previously by Joner and Taylor for published cluster photometry. Given these corrections, we find that within rather generous accidental-error limits, the V systems for the field stars and the clusters agree. With one puzzling exception (namely, b-y for the field stars and the Hyades), recent results published by Stetson agree with ours. Because our result is from direct comparison, we suggest that it should be preferred in this case. However, we also note the need for further comparison between our adopted standard stars and the Gronbech-Olsen stars which Stetson used.

From published FGK-star data, the solar value of (R-I)C is found to be 0.337+/-0.0024 mag. The equivalent value of (R-I)J is 0.343+/-0.0033 mag. The data base which yields these values includes integrated H-alpha and H-beta measurements and also temperatures derived from Balmer-line wings. These latter temperatures can be combined with the quoted value of (R-I)C and data from the infrared flux method to yield a temperature calibration. The result is theta=1.075 (R-I)C+0.510, and is valid for F III-V, G IV-V, and K V stars with 0.06 less-than-or-equal-to (R-I)C less-than-or-equal-to 0.50 mag.

Recently, Taylor has established an [Fe/H] zero point for K giants. Taylor's work permits a reassessment of the well-known mu Leo metallicity of Branch, Bonnell & Tomkin (BBT). Correction to the new zero point lowers the BBT result from +0.48 to +0.35 dex, with the correction being significant at about 97% confidence. It is also possible to set an upper limit on sigma-BBT, the standard deviation of the uncorrected BBT datum. This limit turns out to be 0.17 dex at 95% confidence. Given these results, the corrected datum yields a lower limit at 95% confidence which may be as small as [Fe/H] = 0.12 dex. The BBT result is therefore not decisive evidence for supermetallicity in K giants.

This paper presents "primary" [Fe/H] averages for 373 evolved K stars (see section 4). These stars are of luminosity classes II-IV, and their values of [Fe/H] lie between -0.9 and +0.21 dex. The contributing data are from 58 high-dispersion papers and three spectrum-synthesis papers. The data have been selected (and in many cases, corrected) to be as free as possible from systematic error. References are given with the averages to encourage users to cite original sources. For the stars considered, the data define a "consensus" zero point with a precision of +/- 0.018 dex. In addition, analysis yields rms errors per datum which are typically 0.08-0.16 dex. There is no dependable reduction in the sizes of these errors when sensitive detectors such as Reticons are used. The averaged values of [Fe/H] reflect the consensus zero point, and they are based on weights which follow from the rms errors. The primary data base makes recalibration possible for two large [Fe/H] catalogs. Temperature corrections are necessary for both catalogs, and, while the corrections are 0.12 dex or less for the data of Hansen & Kjaergaard, they are as large as 0.4 dex for a recent survey of Brown et al. The corrected data are included in a "secondary" data base for 669 stars without primary data. Smaller data sets from two additional papers are also included in this data base. Weighting for the secondary data is again based on rms errors. Also given in section 4 are a set of [Fe/H] standard stars and a new DDO calibration. The rms errors for the standard-star data are 0.07 dex or less. These data and the DDO calibration reflect the consensus zero point. For normal K giants, CN-based values of [Fe/H] turn out to be more precise than many high-dispersion results. Some zero-point errors in the latter are also found, and new examples of continuum-placement problems appear. It therefore appears that, at present, high-dispersion results are not invariably superior to photometric metallicities. In section 5 a review is given of high-dispersion and related work on supermetallicity in K III-IV stars. The super-metal-rich (SMR) status of one subgiant (31 Aql) is found to be well established. Despite some assertions in the literature, however, no decisive high-dispersion case can be made at present for the existence of SMR K giants. Such stars may exist, but deciding this question will require further work.
Cousins VRI photometry is presented for 26 stars with continuous scans by Gunn and Stryker. This photometry is combined with literature data and a few unpublished results to critique synthetic colors from the Gunn-Stryker scans. For V - R, it is found that all pertinent results are consistent at the several-mmag level. For R - I, however, systematic differences are found which are most simply interpreted as a declination effect in the Gunn-Stryker scans. In addition, it is found that the Gunn-Stryker synthetic colors are unexpectedly noisy, with sigma per datum of about 0.02 mag. It is suggested that future users of the Gunn-Stryker data keep both these effects in mind.

We present Cousins VRI data for 19 standard stars in the M 67 "dipper asterism". With one exception, the values of σ per mean for these data are less than 10 mmag. Because these stars are close together in the sky, they can be used with economy of effort in standardizing CCD images. For 23 M 67 stars, we report new Cousins VRI photometry. For 22 additional cluster stars, we report new V magnitudes. We find that some published V data for the Hyades and M 67 must be corrected by small amounts to recover the Landolt (1983) zero point. In addition, faint-star M 67 measurements by Eggen and Sandage (1964) display scatter which is not easily interpreted. The same is true for the (largely) bright-star M 67 data of Johnson and Sandage (1955). We also consider the photomultiplier colors of Janes and Smith (1984) and the CCD data of Schild (1983, 1985). For both of these data sets, we find some internal zero-point differences and also some zero-point differences between their data and ours. The Janes-Smith data for red stars have values of σ per table entry in the range 4-8 mmag. For the remaining data from these sources, σ per table entry is in the range 12-20 mmag.