Tuesday, February 1, 2011

The 2011 season is underway

Dear Haumea fans:

The first attempt to observe a mutual event this season is soon to be underway at Siding Spring!

The 2010 HST astrometry has been incorporated into the orbit fit by Darin and the "warning very preliminary" flag has been removed from the 2011 predictions.

Here's what I think I currently know about who is observing when:
(Michele=Bannister, ANU; Heather=Knutson, Berkeley; Mike=Brown, Caltech; Meg=Schwamb, Yale)

2/3    Michele/SSO 2.3m
3/12    Heather/Lick 3m        Mike/Palomar 5m        Meg/WIYN
5/6    Mike/Keck 10m        Meg/WIYN
6/11    Mike/WHT 4m
6/30    Meg/WIYN

If there are any corrections/additions please let me know.

I think this season will be excellent. We now know the rotation period of Hi'iaka accurately and I believe we will be able to phase it up to whenever we get accurate non-event photometry. We also have had a clear detection from HST, so we know that things are actually happening!

There are a couple of nicely placed events that we are missing entirely.

3/4 has an occultation egress visible from the western US
3/22 has an occultation beautifully placed for Hawaii
3/30 is nice from Hawaii and Australia
4/17 is nice from the Canaries
4/28 is nice from Western US/Hawaii
5/16 Hawaii/Australia
6/22 occultation egress Western US/Hawaii


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.