Wednesday, February 18, 2009

Final thought on 1/31 (for now, at least)

Based on all of the data sets and their now pretty good reductions, I have to conclude that we didn't definitively detect the 2009 1/31 event. I would put eyeball limits of ~1% on what would have been a believable detection.

Why no detection?
  • There could have been no event. Examination of the event movie now posted shows that if Namaka's track shifts just a little to the left no event occurs. Or if Haumea is just a bit smaller along on short axis. Either of these is well within the realm of possibilities.
  • The event was too small. Even the nominal prediction was for only a 0.5% event, which is much smaller than we originally thought. The smaller prediction is because of the mixup between inferior and superior events. Had Namaka gone into eclipse, it would have disappeared at the ~1.5% level. Instead, Namaka shadows Haumea, but it only shadows an already severely limb-darkened part of the disk, so only a 0.5% event.
  • The event occurred when no one was watching. I think this scenario is unlikely. With telescopes from New Mexico to Hawaii we did a very nice job of watching the full range of expected event times.

What's next?
  • The 2/18 event (today from Asia) and the 3/09 event (north and south America) are nearly identical to the 1/31 event, arguing that detections will again be hard. By 3/09, however, Haumea will be up for almost the entire night, allowing beautiful full comparison light curves, which might help detect marginal events.
  • The 3/19 eclipse graze is predicted to miss. I don't know of any plans to observe it.
  • The 3/27 transit (Hawaii) could still be shallow, but the full-night light curves will be beautiful for comparison.
  • 4/14 (Asia) starts the best events, as Namaka begins to transit more deeply across Haumea.
  • 4/25 (America) may or may not occur, but, since this is an eclipse, its depth will be significant if it does. And it will tell us much about the dimensions of the rotation axis.
  • 5/03 (America). Almost certainly a very nice event!
  • 5/13 (Eastern Asia). A deeper occultation; should be 1.5%
  • 5/21 (Eastern Asia). An extremely nice transit. Both Namaka and its shadow will almost certainly cross Haumea, leading to a ~3% event with interesting sub-structure.
  • 5/31 (Western Europe/Africa). A deep occultation, 1.5%, but Haumea is now up only part of the night.
  • 6/08; Starting around here the events are long enough and the nights are short enough that no observatory will be able to see the full event. But the events will be deep, so they will perhaps be better recognizable by then. Deep transit.
  • 6/19; deep occultation
  • 6/26; deep transit. hard to observe well.

My conclusion, from staring at all of these, is that April/May will be the best and that, after the fact, we might be able to go back to some of the earlier events and recognize what might have been real events. Stay tuned......

Tuesday, February 17, 2009

Mutual event movies

The main web page now contains links to synthetic movies and predicted light curves of each of the events. The uncertainties here are quite large in time, depth, and duration of event. One of the difficulties is that the transits/occultations are occurring close to the limb of Haumea, so small changes in impact parameter make huge differences. The nice thing about this sensitivity is that a few good detections should strongly constrain the geometry.

While one should not yet take these models too seriously, they are a good indicator of the type of modeling that will be needed to interpret these observations.

Wednesday, February 11, 2009

20090218 shadow transit preparations

I know of the following telescopes that are attempting to observe the Feb 18th (UT) transit of the shadow of Namaka (the satellite) across Haumea (the Kuiper belt object):

  • Terskol 2.0m, Ukraine Maksim Andreev, Olga Zakhozhay
  • Girawali Observatory 2.0m, India, A.N. Ramaprakash
  • Hanle Observatory 2.0m, India, R. Vasundhara, B.C. Bhatt, D.K. Sahu
  • 1.04m Sampurnan Telescope ar ARIES, India, Soumen Mondal
  • Byurakan Observatory, 2.6m, Armenia, Hayk Harutyunian, Tigran MOVSISSIAN, Elena NIKOGHOSSIAN

If anyone knows of other telescopes attempting observations or other people who are at the 5 telescopes above who should be on an email list please let me know!

Lessons learned from 1/31

At this point I've seen the data from all of the telescopes for the 1/31 event and I cannot say for certain whether we detected anything or not (which is unfortunate, because that means we can't reduce the timing error bars for future events yet).

The main difficulty is that most telescopes (in particular, the 3 largest telescopes) had only one night of observation covering about 6 hours at most, so there is not complete overlap of the 3.91 hour light curve. What overlap there is comes from high airmass or deep twilight observations.

The only solution to this problem is to observe for multiple nights, to get a fiducial lightcurve to which to compare. This was done at MRO and the Faukes North telescopes and results are still ambiguous at best.

Much better will be when Haumea is up for ~10 hours in a row in the next month and we can observe 2+ rotations to have a direct comparison. With luck this will make a big difference.

In the meantime, we are trying to construct multiple-rotation light curves by stringing together data from different observatories. This stringing only works if we all use the same filter. In the past I had no recommendation for filter, but after these events I think I will suggest R filters for everyone to all ease of comparison.

Over the next few months we will collect enough full light curves with and without events that I believe we will be able to go back and find the event in the 1/31 data. We might even be able to find it when people do more careful reductions.

In the meantime it is now time to start focusing on the 2/18 event. It will be visible over most of Asia and we know of several ~2m telescopes that are attempting observations.

Friday, February 6, 2009

Sign flip

While attempting to predict the actual events should look like (coming soon to the web page!) we came to an initially horrifying but ultimately only slightly amusing conclusion. First, the horrifying part: there was no eclipse of Namaka by Haumea on 1/31.

What???? We had a half a dozen telescopes on the scene watching nothing? Well, luckily, no.

We just had an error in our projection prediction. Namaka wasn't eclipses by Haumea, Haumea was shadowed by Namaka.


All of the times listed on the web site (and thus all of the times you would observe from a particular spot) were all correct, it's just that the event we were seeing was the opposite.

As of now they have all been fixed.

In the end, getting all of this right is critically important. The interpretation would be completely off if we had it backwards. But for now, I think, no harm has been done. And, I think, everythingis now right.

Wednesday, February 4, 2009

Analysis continues

By now I've seen at least preliminary data from most observing teams and I tentatively think that we detected Namaka going into eclipse. The difficulty is that the eclipse actually takes some time -- ~15 minutes -- during which Haumea is changing rapidly.

As an example of the sort of data to be analyzed, I show below the first reduction data from the Palomar 200-inch telescope (in blue) and the University of Hawaii 88-inch telescope (in black) scaled to match each other as best I could. Times are UT the night of Jan 31, and intensities are relative to field stars.

In this plot you see about 1 3/4 rotations of Haumea. Haumea is elliptical and rotating end over end with -- we think -- one of the faces slightly darker than the other, thus the slight differences between the peaks and troughs 2 hours apart.

The expected signal of the Namaka eclipse is a ~1% dimming of the signal for ~1 hour!

Nothing is obvious by eye, so the analysis requires careful examinations of the before and after light curves. With almost 2 complete rotations we can do that comparison here. Even better, though, at least 2 observatories did observations on separate nights to get good comparison data. These give the best shot of showing something.

I think I know where the event is in the light curve above, as I also compared everything to a well measured light curve from Lacerda (though it is clear that there have been changes from when he observed). But I am eager to hear from the multi-night observations for a better indication.