The period of R Scuti

R Scuti … has coordinates RA 18h 47m 28.95s, Dec -5° 42′ 18″.54 (2000) and is listed in Sky Catalogue 2000 as a variable of type RVa (an RV Tauri object of constant mean brightness) with a range of spectral class G0Iae-K0Ibpv, a V magnitude range 4.45-8.20 and a period of 140.05d. The letter ‘e’ in the G spectrum denotes emission lines; the letters ‘p’ and ‘v’ in the K spectrum denote respectively a peculiar and variable spectrum.
RV Tauri stars are radially pulsating supergiants with alternating deep and shallow minima. RV Tauri itself is generally accepted as being visually the brightest of these. The variability of R Scuti was first noticed in 1795 by E. Pigott, who reported a period of 62.75d in Philosophical Transactions of 1797. (An account of Pigott’s work by M. Hoskin can be found in the Journal for the History of Astronomy.) The change in colour over its variational cycle was first observed by T. E. Espin in 1890.
As might be imagined from its peculiar spectrum and complex lightcurve, R Scuti has attracted much interest and debate since its identification…. (continued…)

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