Eta Carinae Objective Prism Plates

1
Spectra of Eta Carinae from Objective Prism
Photographic Plates
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.
J.D. Cline, T. H. Barker, M. W. Castelaz Pisgah
Astronomical Research Institute
Not-for-profit foundation
AAS 212th Meeting. Session 12.01. June 2008
www.pari.edu
Eta Carinae Objective Prism Plates Plates taken
with Michigan Curtis Schmidt 0.61/0.91-m 10O
prism. 13 Plates in the APDA Archive from 1968 to
1974
E
A
F
B
C
G
Red Spectrum
Scanned image of objective prism plate number
CTIO-10464
H
D
Example of a scanned spectrum of Eta Car. This
spectrum is from CTIO-10464

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.

• 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.

Velocities from measured P Cyg components

• 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)

-558 km/s
-371 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

-497 km/s
-433 km/s

• 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-cen
  ter Contact mcastelaz_at_pari.edu

-493 km/s
-414 km/s