Introduction
description
Transcript of Introduction
Eta Carinae
Zulema Abraham IAG/USP
Introduction
Star itself
Ejecta, Great Eruption in 1840 formed the Homunculus
The 5.52 yr periodicity
Binary vs shell
Homúnculo
Carinae
Homúnculo
Carinae
D = 2.3 kpc
The Star
Frew, JAD 10, 6 (2004)Great Eruption
(1837)
Lesser Eruption(1887-1895)
Homunculus ?
Frew, JAD 10, 6 (2004)Great Eruption
(1837)
Lesser Eruption(1887-1895)
Frew, JAD 10, 6 (2004)Great Eruption
(1837)
Lesser Eruption(1887-1895)
Homunculus ?
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-Davidsonlimit
(Humphreys & Davidson 1994, PASP 106, 1025)
The ejecta
Ejecta: Homunculus in Expansion
Morse et al. 2001, ApJ, 548, L207
1890
1846
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 4.8-24.5 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] 16435 line obtained with the Gemini South telescope
[FeII] 16435
Smith 2005, MNRAS, 357,1330
Ishibashi et al. 2003, AJ, 125, 3222
Homunculus in X-rays
Weis et al. 2004, A&A, 415, 595
0.6-1.2 keV
1.2 -11 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 10830 line intensity
It is anticorrelated with the H-band infrared emission.
Damineli 1996, ApJ, 460, L49Whitelock 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 G287.57-0.59
Car Car
Cox et al. 2005, A&A, 297,168
Retalack, 1983 (1415 MHz)
Car Car
Cox et al. 2005, A&A, 297,168
Retalack, 1983 (1415 MHz)
0
5
10
15
20
25
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45
1990 1992 1994 1996 1998 2000 2002 2004
Epoch (years)
Flux
Den
sity
(jy)
0
200
400
600
800
1000
1200
1 mm
HeI
0
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1990 1992 1994 1996 1998 2000 2002 2004
Epoch (years)
Flux
Den
sity
(jy)
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600
800
1000
1200
1 mm
2 mm
HeI
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1990 1992 1994 1996 1998 2000 2002 2004
Epoch (years)
Flux
Den
sity
(jy)
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200
400
600
800
1000
12001 mm
2 mm
3 mm
HeI
0
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45
1990 1992 1994 1996 1998 2000 2002 2004
Epoch (years)
Flux
Den
sity
(jy)
0
200
400
600
800
1000
12001 mm
2 mm
3 mm
7 mm
HeI
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45
1990 1992 1994 1996 1998 2000 2002 2004
Epoch (years)
Flux
Den
sity
(jy)
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200
400
600
800
1000
12001 mm2 mm3 mm7 mm3.5 cmHeI
Periodicity at mm wavelengths
Last Event (2003.5)
Abraham et al. 2005, A&A, 437, 997
SEST
Itapetinga
SEST
Itapetinga
Last minimum: 7 mm and X-rays
Radio vs X-rays
-505
10152025303540455055
2003.0 2003.5 2004.0 2004.5 2005.0
date (years)
X-ra
ys fl
ux ..
.
0
1
2
3
4
5
6
7
8
7 m
m fl
ux d
ensi
ty (
Jy) .
......
x-raysradio
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
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.,
Davidson (1997)
Data and orbit f romDamineli et al. (1997)e = 0.63
Data f romDamineli et al. (1997), diff erentepoch for periastronand e = 0.67
Data f romDamineli et al. (1997), diff erentepoch for periastronand e = 0.80
Davidson (1997)
Data and orbit f romDamineli et al. (1997)e = 0.63
Data f romDamineli et al. (1997), diff erentepoch for periastronand e = 0.67
Data f romDamineli et al. (1997), diff erentepoch for periastronand e = 0.80
X-rays: wind-wind collisions
Pittard 2003, A&G, 44, 17
Numerical simulations
Pittard & Corcoran 2002, A&A, 383, 636
T 108 K
Density profile (g cm-3)
1.0pp
ss
MM
4103 pM510sM
M /yr 500p
1500skm/sDensity profile
(g cm-3)1.0
pp
ss
MM
4103 pM510sM
M /yr4103 pM
510sMM /yr 500p
1500skm/s
500p
1500skm/s
Position of periastron (near opposition)
Position of periastron (near opposition)
Mass in the line of sight necessary toproduce 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)
125
410 pM M /ano
125
410 pM M /ano
e = 0.9
e = 0.95
e = 0.9
e = 0.95
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 (T107 K, ne1011 cm-3)
Peak at 1.3 mm is not seen because of lack of resolution.
Abraham et al. 2005, A&A, 437, 997
SEST
Itapetinga
SEST
Itapetinga
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
SEST
Itapetinga
SEST
Itapetinga
Fitting the 7 mm light curve
Abraham et al. 2005, MNRAS….
Orbital Parameters
-10
0
10
20
-20 0 20 40 60
time (days)
1.3
mm
flux
den
sity
(Jy)
------
)
0
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2
3
4
7 m
m fl
ux d
ensi
ty (J
y)---
----
7 mm
1.3 mm
0
5
10
15
20
-20 0 20 40 60
time (days)
1.3
mm
flux
den
sity
(Jy)
-----
-
0
5
10
15
20
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.