From: Alex Conley (aconley@panisse.lbl.gov)
Date: Wed May 08 2002 - 22:41:48 PDT
We managed to find a number of reasonably promising candidates in the
SDFw data today. As usual, check sntrak and the finding chart
page ( panisse.lbl.gov/followup/charts/spring_2002 ) for a bit
more information and to look at the tiles. Better magnitudes
are at the end of this email.
One caveat, and it's a big one, is that the magnitudes are royally
f___ed up. The problem seems to be poor APM (USNO, really) matching
leading to nonsensical zeropoint values. I thought that we had this
beat because there were some standard star observations obtained a month
ago that I believed I had managed to kludge in, but apparently I was
mistaken. Hopefully we can improve on this situation tomorrow, but
for the moment I have attempted to make some rough corrections to
the magnitudes. I've done this by comparing the reference zeropoint
that the subtraction software used to what I think it should be based
on the zeropoints from a month ago and the exposure time.
Here is a correction table (this takes magnitudes in the subtraction
to i'(AB) magnitudes, which is what Subaru/SCP chose to calibrate in.
You probably want to subtract abou 0.5 mag to get to Johnson-Cousins I).
This should ONLY be applied to the SDFw subtractions already completed.
chip name chip num delta_mag (add)
scama 6 6.985
scamb 7 2.358
scamc 2 8.195
scamd 3 3.913
scame 8 2.207
scamf 0 1.931
scamg 1 6.318
scamh 5 37.85
scami 4 37.81
scamj 9 6.694
Here the chip num is the DET-ID tag in the header, and we've assigned
the letters out of order to give the chips a vaguely logical arrangement
on the sky (the DET-IDs are arranged in historical installation order,
which turns out to be almost random).
Now -- what does this mean for the candidates that we saved?
For those too lazy to do the math themselves, here's another handy
table:
Name(s) i'(AB)
S02-056 26.33
S02-057 / Balrog 24.96
S02-058 / Bard 23.34
S02-059 / Bombur 26.44
S02-060 / Lotho 25.79
S02-061 / Tom_Bombadil 26.03
Remember you need to subtract ~0.5 to approximate normal I band.
Okay, that was a long email. One last thing
Old Tom Bombadil is a merry fellow,
Bright blue his jacket is, and his boots are yellow.
None has ever caught him yet, for Tom, he is the master:
His songs are stronger songs, and his feet are faster.
Alex
This archive was generated by hypermail 2.1.4 : Wed May 08 2002 - 22:42:08 PDT