1. Eta Carinae Objective Prism Plates Plates taken with Michigan Curtis Schmidt 0.61/0.91-m + 10 O prism. 13 Plates in the APDA Archive from 1968 to 1974 J.D. Cline, T. H. Barker, M. W. Castelaz Pisgah Astronomical Research Institute Spectra of Eta Carinae from Objective Prism Photographic Plates Not-for-profit foundation AAS 212 th Meeting. Session 12.01. June 2008 www.pari.edu The Astronomical Photographic Data Archive North American astronomical photographic data collections stored at PARI Rescue, archive, index, make astronomical photographic data avaliable http://www.pari.edu/library/astronomical-plate-center; Contact: mcastelaz@pari.edu Scanned image of objective prism plate number CTIO-10464 Scanning and Spectrum Extraction Each spectrum of Eta Car was scanned at 4800 ppi with a commercial scanner (MicroTek i800) scanner resolution is 0.6 Å/pixel, and prism spectral resolution is 2Å Scanned images wavelength calibrated based on hydrogen and helium lines. Accuracy of wavelength calibration checked with Harvard Plate X17482 from Humphreys et al (2008) and the comparison is shown in Figure H. Example of a scanned spectrum of Eta Car. This spectrum is from CTIO-10464 FigurePlate/ Emulsion Exposure (minutes) Observation Date (UT) Phase A1760/IIaO6027 Feb 19680.61 B2101/IIaO315 May 19680.65 C3620/IIaO2022 Jan 19690.78 D10464/IIaO2011 Mar 19720.34 E10612/IIaO2017 Mar 19720.34 F15893/IIaO2026 Feb 19740.70 G2538/1N+RG1303 July 19680.68 H (red) H (blue) Harvard X17482 CTIO 10612 45 20 26 May 1941 17Mar 1972 0.79 0.34 Objective prism photographic plates of Eta Carinae (e.g. Humphreys et al 2008, AJ, 135, 1249) were found in the Astronomical Photographic Data Archive (APDA) * located at Pisgah Astronomical Research Institute (PARI). The plates belong to the University of Michigan survey (Houk 1978). These plates were taken from 1968 to 1974 between the 5.54 year cyclic events and therefore represent the usual emission line spectra. The spectrum of Eta Car was extracted from each of the objective prism plates. Discussion Results * Absorption components attributed to P Cyg profile (Thackeray 1953) are measured. Average velocity (shown below) for CTIO plate 10464 = -461 km/sec. Velocities for each profile are designated below lines. -558 km/s -371 km/s -497 km/s -433 km/s -493 km/s -414 km/s Helium line at 4471 Å The helium emission line at 4471 Å marked by arrows in spectrum plots in Figures A-H. Not prominent in the spectra Consistent with results from Humphreys et al (2008) who measured spectra from plates taken between 1892 and 1941 B C D F E PlatePhaseAverage Velocity of P Cyg Component (km/s) 104640.34-461 21010.65-580 158930.70-569 36200.78-475 Average velocity is -521 km/s +/- 60 km/s Expansion since the Great Eruption (160 years ago; Thackery 1953) based on -521 km/s is 7 x 10 16 km or about 8 arcseconds for a distance of 2.3 kpc (Humphreys et al 2008) 8 arcseconds is consistent with the angular size of the Homunculus Nebula (I I shibashi et al. 2003, AJ, 125, 3222) Velocities from measured P Cyg components A G Red Spectrum H