Basic Parameters & Information

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The following notes can be useful for both observers and theorists, and some of these data are not easily available elsewhere. Everyone is welcome to use them, but of course you should acknowledge this site and references mentioned here.

Pronunciation

aay'-tah _ kah-rye'-nee, Approximately rhymes with "ate a high knee".

(In lieu of a classical proper name like Sirius or Vega, some of us have fallen into the habit of saying just "Eta," even if the IAU complains. We wouldn't exercise such familiarity with, say, Eta Aquilae or Eta CMa, but this case is honestly special. Surely this Mad Emperor of the Visible Stars deserves a short familiar name!)

Other names of Eta Carinae

Summary of Basic Parameters

Parameter	Accepted Value	Reference
Distance	2.2 to 2.3 Kpc	Allen & Hillier 1993, Davidson & Humphreys 1997, Meaburn 1999, Davidson et al 2001
Total Luminosity (measured from thermal infrared)	~ 5x106 Lsun MBol~ -12mag ~ 1049 ergs	Westphal and Neugebauer 1969, Cox et al 1995
Zero Age Main Sequence Mass from IR Luminosity	>150 Msun
Current Mass	~120 Msun
Expected Main Sequence Lifetime	~ 3 million years
Current Mass Loss Rate	10^-3 Msun/year	Cox et al 1995, Davidson et al 1995, Hillier et al 2001
Surface Temperature	15000 to 30000 K	Hillier et al 2001
Radius	0.4 to 0.9 AU
Dynamical Timescale	~2 weeks
Thermal Timescale	5 to 500 years dependant on mass fraction considered
Ejected Composition	He & N rich	Davidson et al 1982, 1986, Dufour 1989, Dufour et al 1999
Evolutionary State	near or past end of core H burning
The Great Eruption
Sustained Luminosity	MBol~ -13 Sustained for several years	see History
Peak Luminosity	MBol~ -14
Total Mass Ejected	3 to 15 Msun
Average Mass Loss Rate	0.1 to 0.5 Msun/year

General References

Caution: The subject has more than its share of misunderstandings, and a lot of misleading or incorrect information has been published or appears on the internet. Even such a fundamental quantity as luminosity is a subtle and tricky problem. Aside from recent papers on specific sub-topics noted elsewhere in this site, for background information we currently recommend four general sources, and especially the many papers cited therein:

• A very brief review which takes only a few minutes to read: K. Davidson, in Cosmic Explosions, AIP Conf. Proc. 522 (ed. S.S. Holt & W.W. Zhang, 2000), p. 421.
• Essential pre-1997 references are noted in K. Davidson & R.M. Humphreys, Ann. Revs. Astron. Astrophys. 35, 1 (1997). Also contains explanations, comments, and a list of major unsolved problems.
• Many novel developments appeared at a small but important meeting held after the 1997-98 spectroscopic event. The proceedings volume is Eta Carinae at the Millennium, ASP Conf. Ser. 179, ed. by J.A. Morse, R.M. Humphreys, & A. Damineli (1999).
• The similar book from a later meeting, concentrating on spectroscopic studies, is Eta Carinae and Other Mysterious Stars: Hidden Opportunities of Emission-line Spectroscopy, ASP Conf. Ser. 242, ed. by T.R. Gull, S. Johansson, & K. Davidson (2001).

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