Note: the humble note-taker missed the previous week's meeting thanks to an all-day computer security seminar.
Saul just spoke to Nick Sunstzeff, the chair of the CTIO TAC, and he said that he didn't think people liked to read more than a page. Saul mentioned that we have four or five different uses of the data, to which Nick said that they could be listed on the second page. Saul is most worried about justifying the search for halo white dwarves, as he thinks that is the one which would be hardest to justify in 1/4 of a page (which is all that would be allocated to it).
This led into a discussion of Greg's assertion that recent papers suggest different white dwarf cooling rates. Don pointed out that if you have an area and a temperature, you've got your cooling rate. You would have to change the stored energy so that the E/E-dot would be different. The question is then that according to these models, are white dwarves something different than degenerate Fermi gasses? Greg did not know; he doesn't know enough about the details of the model, only their predictions with respect to detection issues.
Saul yanks things back saying that all we have to do is show that we can go something like a half-magnitude or a magnitude deeper to try to find these things relatie to what we've done before. Saul says his interest is finding the age of the white dwarves; find the oldest one. Right now the oldest is the faintest, with a limit of around 11 Gyr (depending on whose cooling curve you believe), so we find a fainter one, we've probably found an older one. Finding the halo white dwarves is complicated by the fact that the halo is only 1% of the disk hereabouts, so it's hard to find halo white dwarves.
Greg and Saul together started drawing luminosity functions for white dwarves they remembered seeing. Greg showed the measured disk w.d. luminosity function rolling off at something like 10^-4 solar luminosities (a little dimmer than that is 11Gyr). To Saul's challenge, Greg asserts that the rolloff is not an observational selection effect. The models Greg mentioned have the halo white dwarves picking up out there and peaking at 10^-5 solar luminiosities.
Greg wants to look for these halo w.d.'s. We would have to work to find them; a gigantic population of them (as MACHOs) has already been ruled out, although that would have been very easy for us to find. Greg needs to redo the numbers to figure out if 10 square degrees of sky gets us 1 wd or 10 wd's.
At I-band these things will have magnitudes at about 18. Our I-band 3-sigma limit will be somewhere close to 24th magnitude, according to our back-of-the-cerebrum calculations we just bandied about.
The conclusion seems to be that we need to talk to the CTIO people more to find out exactly what we should do, but that we should still keep the description of even this short.
In general, for the proposal, some of the short descriptions will be references to other proposals which will share our data, some we will get sentences from the various people who will be spearheading the different projects.
The paper CONTINUES to iterate. (This is the paper that was just about to be submitted back in April, 1997.) The latest news of it is yet another current version of the spectrum. The data changed as Greg did a more careful job of removing atmospheric absorption features... which changed the date that Peter estimated for the SN. The spectrum was now closer to maximum than we thought it was before. Looking at it, he sais that it's between max and 4 days before max. (Previously peter had assigned -4+-2 days, now he assigns -2+-2 days.)
Don, questioning why this paper is still here when we've been about to submit it for a very, very long time, Saul says that every time we are about to submit the paper, we find something new wrong with it. An HST error bar had a problem... then the spectrum....
One of the latest bits now is that there is a nearby (~1") dim blob that Greg found on the HST image, which (after a calculation error was fixed) turns out to be only some 8kpc away from the SN, if the putative "host" is at the same distance. Greg thinks that maybe it looks like a edge-on spiral, which the SN would be up in the halo (out of the disk) of. From this, you may well just decide not to correct for extinction... the colors are consistent to the 1-sigma level with no extinction.
So... soon the paper is about to go out to all of the group in the various countries, with the idea of the paper be imminently submitted. We shall see.
Around October 23rd... not fully shceduled yet. Alex will be back around for a short while near then, perhaps the week before. Ariel will be around the week before, but not for the meeting itself.
Proposal strategy. Say we are primairly going for 0.9, for the sake of HST. At the same time, we should also find many more than we can follow, so we're hoping on taking ones far from the core. The reason for the 0.9 now is because of the crunch on NICMOS.
Mess because our reference runs are looing at the last quarter half-moon which would be right in front of all of any field we would want to look at. We are trying to get the reference runs moved to a bit later right now. Maybe by next week we will know if this can move.
Scheduling is a problem, because the search run will be immediately after Christmas.
Search runs: Dec 27, 28, with CTIO followup at Jan 4, Jan 5. Then there's a single night at January 25; with luck, Chris Lidman would be able to handle that.
Saul will be gone Thursday the 25th through more or less October 6.