Introduction

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

3. The Star

5. Humphreys-Davidson limit  Carinae: The Star • Luminous Blue Variable • If single M > 120 M • Mass loss rate: 10-4 – 10-5 M /yr • Spectrum: broad and narrow permitted and forbidden emission lines. • No photospheric lines are visible • Some lines present P Cygni profiles (Humphreys & Davidson 1994, PASP 106, 1025)

6. The ejecta

7. 1890 1846 Hubble like expansion law, Curie et al. 1996, AJ, 112, 1115 Morse et al. 2001, ApJ, 548, L207 Ejecta: Homunculus in Expansion

8. 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 4.8-24.5 m images obtained with the 6.5 m telescope from the Magellan observatory

9. 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)

10. Ishibashi et al. 2003, AJ, 125, 3222 Smith 2005, MNRAS, 357,1330 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]  16435 line obtained with the Gemini South telescope [FeII] 16435

11. 0.6-1.2 keV 1.2 -11 keV 0.2 – 11 keV Homunculus in X-rays Weis et al. 2004, A&A, 415, 595

12. The 5.52 yr periodicity

13. Periodicity in the high-excitation lines • Damineli (1996) found a 5.52 years periodicity in the He I 10830 line intensity • It is anticorrelated with the H-band infrared emission. Damineli 1996, ApJ, 460, L49 Whitelock et al. 1994, MNRAS, 270,364

14. Periodicity in the IR

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

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

17. 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

18. edge on disk (Duncan & White 2003)

19. 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 G287.57-0.59 Cox et al. 2005, A&A, 297,168 Retalack, 1983 (1415 MHz)

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

21. Periodicity at mm wavelengths

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

23. Last minimum: 7 mm and X-rays

24. What do the coincidence tell us? • 7 mm flux density is due to the free-free emission from an optically thick disk (density about 107 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

25. Binary vs shell

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

27. 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

28. 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.,

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

31. Numerical simulations T  108 K Pittard & Corcoran 2002, A&A, 383, 636

32. Position of periastron (near opposition)

34. Position of periastron (near opposition)

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

36. 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

37. Position of periastron (near conjunction)

39. Determination of the orbital parameters from the 2003.5 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107 K, ne1011 cm-3) • Peak at 1.3 mm is not seen because of lack of resolution. Abraham et al. 2005, A&A, 437, 997

40. Determination of the orbital parameters from the 2003.5 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

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

43. Orbital Parameters

45. 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.