Forums / The Science / Spectroscopy / The eclipse has ground to a halt spectroscopically !
The eclipse has ground to a halt spectroscopically !
I was able to make good use of a short half hour gap in the clouds last night to take another spectrum of the KI 7699 line. The result is remarkable. It confirms a suspicion I have had for a week or two now that the development in the KI 7699 line has effectively come to a halt, with no significant change since 11th October.
This is third pause I have seen in the KI line development this eclipse, but the first since 16th August when the last one ended and the visual magnitude started to drop. This latest pause coincides with a change in slope in Ic measurements made by Richard Miles (and possibly also in V reported by Des Loughney and other observers)
See this post for more information on my KI line observations
http://www.citizensky.org/forum/poster-paper-pre-eclipse-spectroscopy
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Sorry for the attention grabbing tabloid headline, but I was surprised to see such a significant change in behaviour at this point. Hopefully the acompanying text made the situation clearer. It looks like either the curve that the excess KI absorption is following now is different from that seen by Lambert and Sawyer last eclipse (attached) or the rate of change will have to recover again soon and steepen to get back on track with their data last eclipse.Robin
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Another spectrum from last night (an accumulation of several 5 min gaps in the clouds) shows the KI line Equivalent Width unchanged from 5 nights ago. It is looking like the new slope is very flat, possibly zero. Attached is a comparison with Lambert and Sawyer's data from the last eclipse. I have lined up the dates based on first contact and subtracted a constant 130 mA for the out of eclipse component from the L&S total EW values.Although their data points are sparse, we have clearly departed from the curve seen last eclipse. Where is it going next? Is it just another short plateau from a gap in the disc or will it drop into the mid eclipse "hole" earlier than last time?Exciting times!Robinwww.threehillsobservatory.co.uk
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Still no resumption in KI absorption line development as of 8th November. (updated graph attached) The intensity of the absorption line has now remained unchanged for over 3 week .Robin
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HiAnything new on the spectroscopic front? The photometry data seems to be pointing to a further darkening now after there had been some stagnation for some time (variations of the F-supergiant, maybe..)CSHeinz
Funny you should ask :-) I have just put an update on my website. http://www.threehillsobservatory.co.uk/astro/spectra_40.htm After stagnating for over 5 weeks, the KI 7699 absorption line is on the increase again.The pausedid seem to tally with a temporary slowing of the brightness drop seen by some observers. Unlike the brightness though, the KI line is thought to be unaffected by F star variability so the pause (both in the KI line and in the brightness) is quite likely to be an eclipse effect and not F star variability. This is potentially exciting as it may support the Ferluga multiple ring model. http://adsabs.harvard.edu/abs/1990A%26A...238..270F Robin
Robin and other dear readers: This comment is an attempt to add clarity and to praise Robin's heroic efforts. The choice of words might be clearer when saying "eclipse has ground to a halt". Perhaps you mean to say "the eclipse rate of change in the strength of K I has flattened". Clearly, the semi-opaque body is still present in the line of sight to the F star, because the extra absorption is still very much present. Recall again Steno Ferluga's paper about the disk being composed of rings - based on inflections in the light curve: http://adsabs.harvard.edu/abs/1990A%26A...238..270F . It is noteworthy that your equivalent width versus time study does parallel an apparent change of slope in the V band light curve with an inflection in early October 2009, circa JD 2,455,110 +/- 5 days. If totality is still ~45 days away, more changes in the K I equivalent width might be anticipated. Here's to enough clear weather to find out!