Eta Carinae Objective Prism PlatesPlates taken with Michigan Curtis Schmidt 0.61/0.91-m + 10O 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 212th Meeting. Session 12.01. June 2008www.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

Figure Plate/ Emulsion

Exposure (minutes)

Observation Date (UT)

Phase

A 1760/IIaO 60 27 Feb 1968 0.61

B 2101/IIaO 3 15 May 1968 0.65

C 3620/IIaO 20 22 Jan 1969 0.78

D 10464/IIaO 20 11 Mar 1972 0.34

E 10612/IIaO 20 17 Mar 1972 0.34

F 15893/IIaO 20 26 Feb 1974 0.70

G 2538/1N+RG1 30 3 July 1968 0.68

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

Plate Phase Average Velocity of P Cyg Component (km/s)

10464 0.34 -461

2101 0.65 -580

15893 0.70 -569

3620 0.78 -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 1016 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 (IIshibashi et al. 2003, AJ, 125, 3222)

Velocities from measured P Cyg

components

A

G

Red Spectrum

H