Akademik Veri Yönetim Sistemi
IV. Jornadas de Astrofisica Estelar, Tucumán, Arjantin, 22 - 24 Haziran 2022, ss.22-32
Abstract. We review the work of the three senior coauthors and their collaborators on the elemental abundances of mostly single normal and chemical peculiar B, A, and early F stars and field horizontal branch A stars especially in the optical region. We began in the era of taking and processing photographic spectra with powerful spectrographs such as those at the Dominion Astrophysical Observatory (DAO), David Dunlap Observatory (DDO), Mt. Wilson Observatory, and Kitt Peak National Observatory and then progressed to using electronic devices at the DAO including a Reticon and two charged coupled devices (CCDs) since when they became available as they were superior detectors. Initially we scanned the photographic plates using in house microdensitometers outputting the spectra on chart recorders and measuring them with planimeters and measuring engines. These analog approaches were replaced by computer controlled PDS microdensitometers producing digitized spectra displayed and analyzed on computer graphics displays. Model atmosphere techniques replaced methods involving the curve-of-growth. When Pintado and Yüce began working with the three senior coauthors we obtained some spectra from observatories in their home countries. Gulliver and Alan Irwin began the conversion to digitized spectra analysis using a PDS microdensitometer and PDP-8 minicomputer at DDO in the early 1970s producing a program called REDUCT that was capable of producing digitized rectified spectra from photographic plates. Gulliver transplanted that program to DAO in the mid-1970s and began a career long collaboration with Graham Hill that saw the development of multiple analysis programs including the next generation fundamental program REDUCE. To improve our analyses, we started a major upgrade to the programs we use to reduce and analyze our spectrograms, and then to derive elemental abundances. Further for the last decade we obtained spectra from the CHIRON echelle spectrograph at CTIO. Based on our prior experience we created our own pipeline programs to optimally coadd sufficient spectra to produce a final normalized coadded spectrum for each star covering lambda4100–6900 with S/N values of at least 500 with 2-dim polynomial wavelength solution and cosmic ray removal.