Eta Car MONITORING CAMPAIGN
Link to Mike Corcoran's page: X-ray light curve
June/2004 - Steiner andDamineli, when analizing the spectra collected during the 2003.5 spectroscopic event, made a surprising discovery: the HeII 4686 A shows upd strongly exactely when all other emission lines were fading! This is the first direct evidence for the wind of the invisible companion star. Click on the links to download the PDF file of the paper just submitted to ApJ Letters (etacar_heII.ps.zip: 80 Kb, etacar_heII.pdf: 80 Kb ).
12-14/December/2003 - Observation conducted at Pico dos Dias Observatory (LNA/Brazópolis) by José Henrique Groh and Augusto Damineli have shown that the spectroscopic event is ending. All spectral lines that faded on June/2003 are back, except for [Ne III] 3868 A, the one that needs the highest energy to be excited. We believe that this line will reappear along the next weeks. It is interesting to note that this line is absent from the spectrum for 22 weeks, twice the time the duration of the minimum in X-rays.
We have noticed also (as a matter of fact since 1996) that the line intensities are decreasing from cycle to cycle. In the plot below, we display the He I 6678 A line in the same phase of the 2025 days cycle (~phase 0.08). We call cycle 11 the one that started on June 29, cycle 10 in December 1997 and cycle 9 in June 1992. This indicates that some component of the system is evolving secularly, altough it is not clear if such a component is the wind of the primary star or the circumstellar material. The fact that the P Cygni absorption component of He I (plus H I and Si II) is becoming deeper with time, is an indication that the wind of the primary star is becoming optically ticker.
Click on the link to download a repport we just submitted to IBVS ( PDF format 90 Kb)
June 12th to July 1st - The first spectral line to disappear completely was [NeIII] 3868 A, that has the highest excitation potential in the optical spectrum of eta Carinae (fist panel below). The observation was made on day 22.9 (Greenwich time), but the plot indicates that the real minimum started on 22.5. My method to derive the period lenght of the 5.5 year cycle is based on the disappearance of the narrow component of HeI 6678 (second panel). In the ongoing event, such a spectral component was recorded as zero on July 1st. However, since July 26th that feature was very faint, only measurabel in spectra of very high S/N ratio. In spectra with the same S/N ratio of the 1997.9 event such a feature would not be measurable and would be assumed to be zero. In tjis way, if we degrade the present spectra to the same S/N as in the previous event, it would be stated to be zeroed on July 26th, implying that the priod is 2026+-1day. In fact, such a period lenght brings a good agreement between the two events (1997.9 AND 2003.5) through all the descending phase.
May 29 and June 12th- Filled blue circles are measurements of the narrow component of HeI 6678 A line made on May 29th and June 12th. Red squares are measurements made in the last event (November and December 1997). The red solid line is a linear fit through those data (red squares). By shifting the previous event by 2020 days, the predicted disapearance of the narrow component in the HeI 6678 A line should occour on June 25th (around 17 hs UT.- but dont take the hours and even the day too seriously...). The present cycle seems to be following well the predictions. At least more smoothly than in X-rays. If Mike Corcoran's blood pressure follows his X-ray light curve, he needs to see his doctor immediatly!
13 and 26MAY/2003 -
R/V peak intensity ratio - The "Red" peak continued to decrease, but the "Violet" peak remained almost unchanged. The "Violet" peak is expected to crash along the next month.The left panel shows the line profile in units of radial velocity. The panel at right shows the peak intensity ratio as a function of phase. Notice that these spectra were taken with a thinned CCD, plenty of fringes as usual. After removing the fringes the spectrum is very nice, with S/N~100 in the continuum with an expsoure time of 10 minutes in a 1.6-m telescope.
Radial Velocity of the HeI 6678 A line- The broad component of this HeI line returned to the same value it had a month ago. This looks surprising, short-term variations also occurred in the previous cycle.
13 and 14/APRIL/2003. (Measurements made at Pico dos Dias Observatory: LNA/Brazil) The spectral line HeI 10830 A continued to faint. The V/R ratio (ratio of intensities between the "Violet" and the "Red"" peaks) continued to increase (blue line), follwoing the same pattern as in the previous cycles (cycle 09 and cycle 10). The absolute values of the peak ratio intensity is decreasing because the stellar continuum is secularly increasing.
The radial velocity of the broad component of HeI 6678 continued to decrease. The last two measurements indicate a sudden decrease, that might be real or an observational error in the previous point (March/2003). The general behavior of the RV curve is following nicely the previous cycles, indicating that the new "event" is approaching.
The spectroscopic event predicted to occur in 2003 is already on the way. Spectra collected at Pico dos Dias Observatory (LNA/Brazil) show that the intensity of line HeI 10830 reached a peak in 2002. After that, started decreasing as in the past events. The last point in the plot below (red x) was measured on March 15th, 2003. The rate of decreasing in the equivalent width was ~3 A/month along 2002 and changed to ~11 A/month in the begining of 2003. If the period P=2020 days is real, the next phase of minimum will start on June 28th, 2003.
The plot below display the HeI 10830 A line profile. The spectrum in red color (spectral resolution V=15 km/s) was collected in December 20th, 2002 and the blue one in March 15th, 2003. The V peak remained fainter than the R peak along the last 5 years. The inversion of the peak ratio (now V>R) is a trigger for the event. This spectrum, compared with we got in March 20th, 1992 gives a lower limit of 2005 days for the period, what is compatible with the 2020 days claimed by Damineli et al 2000.
The plot below display the progress of the 2003.5 event as seen in the radial velocity of HeI 6678 broad line component. The last point was measured on March 15th, 2003 at Pico dos Dias Observatory (LNA/Brasil). Although the nature of the velocity shifts in this spectral feature is not clear, it is crucial to check the stability of the period. In the case the phase of minimum excitation starts inbetween June 18th and July 8th, 2003, the periodicity is real, what gives a strong support for the binary model proposed by Damineli, Conti and Lopes (1997).
OBSERVATIONS SCHEDULED to the PICO DOS DIAS OBSERVATORY (LNA/BRAZIL)
Telescope: 1.6-m Coudé Focus (gratings A=600g/mm and B=1800g/mm) and Cassegrain IFU
A- Resolution=12000 at 6000 A (R=20000 at 10800A) spectral coverage = 1100A
B- Resolution=36000 at 6000 A, spectral coverage~360A
C- Resolution=10000 at 6000 A, Integral Field Unity; field coverage=30x15"
X- Not measured
Authors: Coudé -Augusto Damineli, Nelson V. Leister, Ronaldo S. Levenhagen; IFU - Jacques Lèpine
We thank to LNA TAC for the generous time allocation for this monitoring program
|date||setup/centr. Wav. (A)||status|
|15||A/6750A, 10600A||OK - IAUC8100,|
|12||A/3500-11000A||.OK A/10400, A/6750|