Wednesday, August 5, 2009

Hi'iaka rotates!

For those of you who, like me, have been looking at data and scratching your head wondering why two rotations in a row of Haumea don't match even when there is no mutual event going on, I now strongly believe the answer is that Hi'iaka rotates with an approximately 10% light curve and an approximately 8 hour period. Hi'iaka is usually within the aperture for the photometry, so this gives an additional 1% light curve to Haumea at an 8 hour period. The effect looks frighteningly like a mutual event. If one knew the phase, period, and amplitude precisely one could subtract it out and still see mutual events, I think. But finding those paraemters requires more observations when there >aren't< mutual events, rather than when there are. We might have enough data from all of the observers to be able to piece something together though.

The moral is: this will take much more work than initially anticipated, but it is (perhaps) less bleak than it appeared when the data didn't make any sense.

Monday, May 4, 2009

2009 05 03 event

Almost all observers who attempted Haumea last Saturday had significant weather problems, from the southwestern US to Brazil. Hawaii was clear, and data were collected, but it was almost certainly after the event had already taken place. It appears we have no detection and no particularly useful upper limits.

We have had a pretty rough time of it lately, and, to date, we have no detections. I would have hoped with the northern spring weather coming around we would have a detection or two by now, but, no.

We only have a few good shots for the rest of the season:

  • 5/13: First good occultation, visible from eastern Asia and Indonesia and [barely] Australia. We know of attempts from the 1.8m Bohyun telescope in Korea, the 2.0m Girwali telescope in India, and the 2.3m ANU telescope in Australia.
  • 5/12: A very deep transit, visible from eastern Asia and Indonesia and [better this time] Australia. The 2.3m ANU and the 1.8m Bohyun telescope are observing.
  • 5/31: Haumea is now up for only a fraction of the night, making observations harder. This event is a ~5 hour long occultation. Observations are being attempted from the Nordic Optical Telescope (Canary Islands), the 1.8m Pico des Rios in Brazil, and the 6.5 m Magellan telescope in Chile.
After May the amount of time that Haumea is up for the night gets small so observations get quite difficult. There are another ~4 events that are worth attempting to observe, but if we don't get anything in May we are going to be in very bad shape!

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.

Friday, January 30, 2009

Good weather for tonight

All is set for our attempt tonight. Amazingly, it looks like the weather forecast is good for southern California (Palomar), southern Arizona (Vatican Observatory), southern New Mexico (Apache Point, Magdalena Ridge Observatory), and also Mauna Kea and Haleakala (UH 88inch and Faulkes 2m, respectively). I believe this to be some sort of record.

Bill Ryan at MRO got a nice comparison light curve from last night, which will be quite useful for definitely identifying tonight's event.

Between all of the observatories we will have two full rotations, so even thought it might be painful, I believe we will be able to stitch together a full dataset for comparison.

Wednesday, January 21, 2009

Jan 13th eclipse

no known attempts

Jan 5th transit shadow graze

no known attempts

Dec 26th eclipse

Attempts were made from Bulgaria and Armenia (on Christmas night!), but complete cloud cover prevented any telescopes from opening.

Dec 18th transit shadow graze

No known attempts

Dec 7, 2008

no known attempts

Tuesday, January 20, 2009

Observing strategy

The main goal for these observations is to obtain accurate relative photometry with sufficient cadence to resolve the events (ingress and egress each last ~15 minutes, but there might be interesting structure within) and sufficient accuracy to detect the event (Namaka's disappearance during an eclipse will make the overall brightness of Haumea decrease by only about 1.3%).

The optimal exposure time for your observations depends on your telescope and on your camera. The main things to worry about are:
-readout time for your camera
-time to saturation
-time until you are sky background limited

I would shoot for having exposure times be at least 2-3 times the readout time of your camera, as long as you are not coming close to saturating Haumea. Even with a very fast readout camera, exposure times under a minute or two are probably not worthwhile. The best cadence, if it fits your camera characteristics, is probably around 2 minutes per exposure. At Palomar, we will be doing 2 minute exposures with 45 second readouts in between.

Previously I said this:
In general, the optimal filter is the one that gives you the highest signal-to-noise. Haumea is almost precisely solar colored, so observing in something like a V filter is a good bet, though it is possible that you might want to go totally unfiltered (at Palomar we will be using a special filter that cuts out some of the worst of the sky lines from the bright Palomar sky).

However, after the 1/31 event I now believe that it is best if everyone observes in as common a filter as possible. Because some of the events will have heavy moonlight, R seems the best choice. At Palomar we used a slight variant of R that cuts out the strong sodium lines from San Diego, but as long as everyone is R-ish I think we will be able to compare all of the data well.

At some point in the night you will want to insert a single image in a different filter. This single image will be used to get the colors of all of the stars relative to Haumea. The relative photometry can then be done using only stars that are close to Haumea's solar color. This selection will be important given the very wide range of airmasses Haumea is likely to go through (at Palomar we will start at an airmass of 4!).

Before Haumea rises (or on an earlier night, at twilight, or with dome flats):
  • take images of the night sky/twilight sky or just dome flats
  • look for a particularly well behaved region on the chip where the flat field is as flat as possible, there are no bad pixels or columns, nothing funny is going on for a moderately good sized region.
  • Note that location for later; that is where you will put Haumea

The observing strategy is quite simple:
  • point to Haumea as early as your telescope possibly can.
  • place Haumea in the very nice region of the chip that you identified earlier.
  • track at Haumea's rate; do not dither! Dithering is great if you want to average out CCD variations over time, but we instead want to keep them constant with time.
  • observe all night until you can't anymore
  • pause for nothing.
  • if you fear focus changes, focus on an image-by-image basis rather than stopping to focus.
  • Be sure to insert one or two images in a second filter.
We believe that the best strategy will be to track on the rate of Haumea but perform no dithering of the telescope. If your telescope cannot track at a moving target rate, track siderally, but, again, perform no dithering.

If you believe your night to be photometric, good solar colored standard stars at the begining and end would be helpful, but not essential.

Jan 31: Our first good attempt

The first good attempt to observe a mutual event will come on Jan 31st UT (the night of Friday, Jan 30th), as Namaka goes into the shadow of Haumea. The ingress is predicted for 11:02 UT = 3:02 AM PST Thursday morning; the egress follows almost one hour later at 11:52 UT = 3:52 PM. The uncertainty in the timing, however, could be as much as 3 or 4 hours!

This event is particularly important, because if we can get just one good clear detection, we will greatly decrease the uncertainty in the times of all future events.

To my knowledge, the following telescopes/observers are attempting observations:

Palomar 5m (Caltech group)
Apache Point 3.5m (Nancy Chanover & Chas Miller)
Magdelena Ridge 2.4m (?)

University of Hawaii 2.2m (Emily Schaller)

We are in good shape to get somebody to see this event unless the entire western US is clouded out. Which can definitely happen this time of the year. We should have eyes on the event if it occurs anywhere from about 4 hours early until about 8 hours late.

Our difficulty for fast analysis of this event will be that no one will be able to observe more than about 5 hours. Haumea rotates every 4 hours. Ideally, one would observe for 8 hours and see Haumea with and without an event. With luck, though, we will be able to stitch together enough observations to get this figured out very quickly. We would like to know in time for the Next event, occuring on Feb 18th, over India and China.

Welcome to the Haumea Namaka mutual events page

I will continuously update this sight throughout the season to give as much up-to-the-minute information as possible on the mutual events. To learn more, please read the full mutual event page.