the most luminous star (known)

The most luminous star

(known)Augusto Damineli

IAG-USP

Carinae survived a giant outburst ~10 49.5 ergs => unknown physical mechanism!

•Was seen at naked eye in daylight (~Sirius)

•Well documented history along 150 years

•The light of distants galaxies (=young) is dominated by massive stars.

•Massive stars are very rare in the local Universe and unresolved in distant galaxies.

•Eta Car is close (2.3 kpc) and easy to observe by any technique

•Interacting galaxies also form lots of massive stars (blue)

•Massive stars are important sources of N, He and other heavy elements

•Star models (evolutionary tracks) in the upper HR diagram are poorly known

Why is Carinae important?

O

typ

e st

ars

Humphreys-Davidson limit

S Doradus Oscillation

LBV

Nitrogen >> Solar

Oxigen << Solar

90% of star mass is lost in the LBV phase

mV

0

2

4

6

8

Mbol=-12.3

1843.2

The 1843 giant eruption•tidal interaction in a binary system (Innes 1903)

•slow supernova (Thackeray 1956, Zwicky 1965, Rodgers & Searle 1967)

•pulsar embedded in a supernova remnant (Ostriker & Gunn 1971, Borgwald & Friendlander 1993)

•compact object accreting mass from a companion (Bath 1979, Warren-Smith et al. 1979, Tutukov & Yungel'son 1980; Viotti et al. 1989, Gallagher 1989, van Genderen, de Groot & The’

•pre-main sequence star (Gratton 1963)

•massive main sequence star (Burbidge 1962, Tamman & Sandage 1968, Burbidge & Stein 1970, Talbot 1971, Davidson 1971, Hoyle, Solomon & Wolf 1973, Humphreys & Davidson 1979, Davidson, Walborn & Gull 1982, Doom, De Greve & Loore 1986)

•atmospheric instability in massive post-main sequence star (Andriesse, Packet & de Loore 1981)

•dynamical instability in a extended atmosphere (Stothers & Chin 1983, Maeder 1983)

•long period CWB (Damineli, Conti & Lopes 1997

equatorial disc 110 years

500 x Solar sy

stem diam

eter

bipolar fl

ow 150 years 600 km/s

previous ejections ~1000 years

scale

Features

1”

central object unresolved

5x106 L

The 5.53 year cycle

Damineli 1996

Conflict with the Conflict with the dominant idea: dominant idea: S Doradus cycles S Doradus cycles

should be should be unpredictable!unpredictable!

This was a This was a predictionprediction

The binary modelThe binary model

69M (secondary)

<=113 M

<=89 M

67 M (primary)

600 km/s 1400 km/s

X-rays ~80 million K

600 km/s 1400 km/s

6 million K83 million K

Homunculus 6 million K

Central source 83 million K

Prediction: variable hard X-raysPrediction: variable hard X-rays

1992.5

1994.7

1998.0

X-rays ROSATX-rays ROSAT

1992.5

1994.6

1998.0

The predicted event for 1997/8 came on schedule!

The periodicity is true P=5.530.01 years

Shell ejectionShell ejection

XX

Binary modelBinary model

•Same speed and mass

•Same energy cycle after cycle

Colliding wind binary model reproduce

observed X-ray flux, temperature, NH

3 milhões K

60 milhões K

raios-X óptico

rádioinfravermelho

Is binarity related to the 1843

giant eruption?

•Visible/NIR: LNA, ESO, CASLEO, South Africa, Australia

•Radio: Itapetinga, Australia, SEST(ESO)

•X-rays: RXTE, Chandra, XMM

•UV: Hubble