A STUDY OF THE SECULAR VARIATION OF THE HIGH-AMPLITUDE DELTA SCUTI STAR AD CMI

We determine the nature of the Delta Scuti star AD CMi and its physical parameters from newly determined times of maximum light and other times from the literature, as well as from uvby −β photoelectric photometry.

A STUDY OF THE SX PHE STAR BL CAM

We determined the physical parameters of the SX Phe star BL Cam from newly available times of maximum light and other times from the literature, as well as from uvby − β photoelectric photometry. From our analysis we found that this star is a binary system. The mass of the companion star was calculated in term of the mass of the primary star and the orbital angle. For this star we determined a metallicity [Fe/H] of −1.2 ± 0.3.

Constructing the Electric Eye: Situating the Smithsonian National Air and Space Museum’s Wisconsin Collection of Photoelectric Detectors in Historical Context

Between 2017 and 2019, the Smithsonian National Air and Space Museum acquired a collection of photoelectric tubes used in the earliest program of astronomical photoelectric photometry at the University of Wisconsin. The Wisconsin Collection of Photoelectric Detectors represents a unique look inside the development of a pioneering research project and a fledgling technology. The process by which techniques and technologies related to photoelectric photometry developed in the early twentieth century involved a variety of academic disciplines and commercial actors, and this process is reflected in the variety and specific features of the tubes in the collection. This paper attempts to situate the Wisconsin Collection within the wider development of photoelectric tubes as a technology, the development of observation techniques at Wisconsin, and their contributions to astronomical knowledge.

PHOTOMETRIC STUDY OF THREE SHORT PERIOD VARIABLE STARS

We have obtained uvby − β photoelectric photometry with the 0.84 m telescope at the San Pedro Mártir Observatory, México, for the stars HD 115520, HD 220735 and HD 26738. The first two had been previously determined to be variables whereas the last one is being reported here as a new variable. With an extended time basis for the first two, we have determined their period of pulsation, which is found to be stable. Physical parameters are presented for the three stars.

ON THE NATURE OF THE HADS STAR V2455 CYG

Using uvby − β photoelectric photometry obtained with the 0.84 m telescope of the Observatorio Astrónomico Nacional de San Pedro Mártir, México, we determined some of the physical characteristics, such as effective temperature and surface gravity of the high amplitude Delta Scuti star V2455 Cyg (=HD 204615). Newly determined times of maximum light gathered at the Observatorio Astrónomico Nacional de Tonantzintla, México with small 10 inch telescopes equipped with CCD cameras were combined with times of maxima in the literature, and used to study the secular variation of the pulsational period of the star.

STUDY OF THE OPEN CLUSTER NGC 1528 THROUGH uvby − β PHOTOELECTRIC PHOTOMETRY

uvby − β photoelectric photometry of sixty-five stars in the direction of the open cluster NGC 1528 is presented. From the uvby − β photometry of the cluster we classified the spectral types of the stars which allowed us to determine the reddening (E(b-y) of 0.196 ± 0.054) and hence, their distance, in parsecs, of (954 ± 154). We determined membership of the stars to the cluster and the age (Log age equal 8.04) of the cluster. A metallicity [Fe/H] of −0.31 ± 0.08 was calculated.

SOME REMARKS ON THE OPEN CLUSTER UPGREN 1 USING uvby − β PHOTOELECTRIC PHOTOMETRY

The open cluster Upgren 1 presents peculiar features that in the past led to divergent opinions about its existence. In previous studies of other clusters, uvby − β photoelectric photometry has shown results in agreement with other techniques; therefore, the photometry obtained in the present work has been combined with data from previous studies to examine the brightest stars in the direction of the cluster. Analyzing the unreddened indexes, we found that all the stars are of late spectral types. Applying the empirical relations of Nissen (1987) to determine the reddening and, consequently, the unreddened indexes, we found that all but three are located at a distance of 123 ± 17 pc. The assigned membership in this study is in concordance with that of Upgren, Philip and Beaver (1982) obtained through radial velocities.