Introduction Star itself Ejecta, Great Eruption in 1840 formed the Homunculus The 5.52 yr periodicity Binary vs shell D = 2.3 kpc

The Star

 Carinae: The Star Luminous Blue Variable If single M > 120 M Mass loss rate: – M /yr Spectrum: broad and narrow permitted and forbidden emission lines. No photospheric lines are visible Some lines present P Cygni profiles Humphreys-Davidson limit (Humphreys & Davidson 1994, PASP 106, 1025)

The ejecta

Ejecta: Homunculus in Expansion Morse et al. 2001, ApJ, 548, L Hubble like expansion law, Curie et al. 1996, AJ, 112, 1115

The Homunculus at the IR Ejected mass was calculated from the visual extinction and line emission as 2.5 M (Davidson & Humphreys 1997) Mid to far-IR ISO observations showed a spectrum compatible with three T dust emission from 15 M (Morris et al. 1999). Smith et al. (2003) came to the same conclusion from  m images obtained with the 6.5 m telescope from the Magellan observatory

LBV or supernova? Morris et al. 1999, Nature, 402, 502 (dust torus in the equator) Smith et al. 2003, AJ, 125, 1458 (dust at the poles)

The Little Homunculus Ishibasbhi et al. (2003) dicovered the LH using the long-slit Space Telescope Imaging Spectrograph Smith (2005) presented Doppler tomography of the [Fe II] line obtained with the Gemini South telescope [FeII] Smith 2005, MNRAS, 357,1330 Ishibashi et al. 2003, AJ, 125, 3222

Homunculus in X-rays Weis et al. 2004, A&A, 415, keV keV 0.2 – 11 keV

The 5.52 yr periodicity

Periodicity in the high-excitation lines Damineli (1996) found a 5.52 years periodicity in the He I line intensity It is anticorrelated with the H-band infrared emission. Damineli 1996, ApJ, 460, L49 Whitelock et al. 1994, MNRAS, 270,364

Periodicity in the IR

Periodicity at optical wavelengths Fernandez Lajus et al. 2003, IBVS, 5477

Periodicity at X-rays (RXTE) Corcoran 2005,AJ, 129, 2018 Dec 1997 Jun 2003

Radio Images with ATCA Observed at 3 and 6 cm with ATCA since 1992 (Duncan et al. 1995,1996) Different structures show different velocities Slow velocity region has an edge-on disk-like structure

edge on disk (Duncan & White 2003)

Radio Observations at SEST and Itapetinga Observed with SEST at 1.3, 2 and 3 mm Flux density increases with frequency Variable light curve, in phase with optical emission At Itapetinga, scans across the source, calibrated with G Cox et al. 2005, A&A, 297,168 Retalack, 1983 (1415 MHz)

Cox et al. 2005, A&A, 297,168 Retalack, 1983 (1415 MHz)

Periodicity at mm wavelengths

Last Event (2003.5) Abraham et al. 2005, A&A, 437, 997

Last minimum: 7 mm and X-rays

What do the coincidence tell us? 7 mm flux density is due to the free-free emission from an optically thick disk (density about 10 7 cm -3 ) Sharp minimum is produced by a decrease in the number of available ionizing photons (recombination time of the order of hours) Decrease in the number of photons is due to absorption of UV radiation by dust The same material that absorbs the UV absorbs X-rays

Binary vs shell

Shell events Zanella, Wolf & Stahl 1984, A&A, 137, 79

A binary system? The 5.52 yr periodicity was also found in the radial velocity of the broad component of the Pa lines. It was compatible with a binary system with eccentricity e = 0.6 Minimum in the He I line curve occurs at periastron passage Predicted strong wind-wind interactions Damineli et al. 1997, New Astr., 2, 107

Orbital Parameters: eccentricity The orbital parameters were not very well determined Davidson (1997) use the same data and gave different parameters, specially higher eccentricity Davidson 1997, New Astron.,

X-rays: wind-wind collisions Pittard 2003, A&G, 44, 17

Numerical simulations Pittard & Corcoran 2002, A&A, 383, 636 T  10 8 K

Position of periastron (near opposition)

Mass in the line of sight necessary to produce the observed absorption

Dust formation near periastron Two shocks form at both sides of the conical contact surface Near periastron the density of the shocks is very high and the region cools radiatively After the secondary star moves in the orbit, a cold region can be formed between the two shocks and dust can grow. The accumulated dust absorbs X-rays and optical emission Falceta-Gonçalves, Jatenco-Pereira & Abraham 2005, MNRAS, 357,895

Position of periastron (near conjunction)

Determination of the orbital parameters from the event Decrease in the radio flux is due to the decrease in the number of ionizing photons Peak seen at 7 mm was due to free-free emission from the shock (T  10 7 K, n e  cm -3 ) Peak at 1.3 mm is not seen because of lack of resolution. Abraham et al. 2005, A&A, 437, 997

Determination of the orbital parameters from the event Shock material is optically thick at 7 mm and optically thin at 1.3 mm The material of the secondary shock produces most of the flux density The observed light curve at 7 mm is explained by geometrical factors. Abraham et al. 2005, A&A, 437, 997

Fitting the 7 mm light curve Abraham et al. 2005, MNRAS….

Orbital Parameters

Conclusions (personal) Star: LBV or supernova? Still unknown Binary system or shell event: both Orbital parameters: only determined from radio at periastron passage: they imply that periastron is close to conjunction.