Supernova 2006aj Comparison Star Magnitudes
See GCN 4898
In order to calibrate our CFA FLWO 1.2m photometry for SN2006aj/GRB060218 we observed Landolt
standards over a range of airmasses, in UBVRri on the night of March 4, 2006 UT.
We present our V-band light curve in Modjaz, et. al. 2006 (ApJ, 645, 21; astro-ph/0603377).
Our UBVR photometric solution was based on the magnitudes
given in Landolt, 1992. For our SDSS filters we used the r'i' magnitudes given in Smith, 2002. We applied these photometric solutions to 9 comparison stars
in the field of SN2006aj (see below). Our magnitudes agree well with those found
at http://brucegary.net/GRB060218/x.htm
. It should be noted that our u'BVRr'i' magnitudes (u' is derived
from our UBVRr' values) are respectively 0.81, 0.40, 0.27, 0.20, 0.23 and
0.15 mag fainter than those derived from or presented in
GCN 4777 by Cool, et.
al. at
http://mizar.as.arizona.edu/~grb/public/GRB060218. From the
SDSS website, we used Rodgers et al. (2005) to calculate u' from our UBVRr' data.
We also used Lupton (2005) to calculate BVR mags from the SDSS values and
we used the
SDSS transformation to convert between ugriz and u'g'r'i'z'.
This has been brought to their attention and in investigating this
photometric offset, R. Cool has discovered calibration offsets between
the two SDSS photometric reductions of this field indicating possible
non-photometric conditions or other calibration problems in the SDSS
photometry. The problem is being investigated to ensure data with
suspicious photometric quality will be flagged as such in future SDSS GRB
releases.
All stars except for star 7 are also SDSS stars. We hope that these magnitudes are useful to the SN and GRB communities.
You are welcome to use these for your research. In any publications using
these magnitudes, please cite Hicken et al. 2006, (GCN 4898) and our paper by
Modjaz, et. al. 2006 (ApJ, 645, 21; astro-ph/0603377).
We also observed the field of SN2005am on this night and found our UBV
magnitudes of 11 comparison stars to agree well with those listed by Li et.
al. in
astro-ph/0505504, bolstering our
confidence in our calibration for SN2006aj.
SN2006aj/GRB060218 Comparison Stars
 |
| Star |
RA |
DEC |
U |
B |
V |
R |
r' |
i' |
| s1 |
03:21:42.767 |
+16:51:39.47 |
16.674 +/- 0.053 |
16.168 +/- 0.020 |
15.212 +/- 0.012 |
14.672 +/- 0.009 |
14.914 +/- 0.009 |
14.634 +/- 0.011 |
| s2 |
03:21:16.375 |
+16:54:08.99 |
15.982 +/- 0.042 |
15.685 +/- 0.017 |
14.936 +/- 0.009 |
14.508 +/- 0.008 |
14.726 +/- 0.008 |
14.540 +/- 0.010 |
| 3 |
03:21:39.748 |
+16:51:30.40 |
17.353 +/- 0.077 |
16.398 +/- 0.023 |
15.276 +/- 0.012 |
14.622 +/- 0.008 |
14.884 +/- 0.008 |
14.508 +/- 0.010 |
| 4 |
03:21:40.529 |
+16:53:09.89 |
17.787 +/- 0.095 |
17.075 +/- 0.039 |
16.002 +/- 0.019 |
15.381 +/- 0.013 |
15.643 +/- 0.013 |
15.288 +/- 0.014 |
| 7 |
03:21:22.533 |
+16:54:05.02 |
13.884 +/- 0.035 |
13.730 +/- 0.011 |
13.076 +/- 0.006 |
12.685 +/- 0.006 |
12.897 +/- 0.006 |
12.740 +/- 0.008 |
| 8 |
03:21:25.221 |
+16:51:12.44 |
16.579 +/- 0.050 |
16.432 +/- 0.022 |
15.692 +/- 0.014 |
15.258 +/- 0.012 |
15.497 +/- 0.012 |
15.277 +/- 0.013 |
| 10 |
03:21:45.861 |
+16:54:24.68 |
16.607 +/- 0.050 |
16.501 +/- 0.025 |
15.839 +/- 0.015 |
15.424 +/- 0.013 |
15.631 +/- 0.013 |
15.427 +/- 0.014 |
| 11 |
03:21:43.804 |
+16:54:43.47 |
17.043 +/- 0.059 |
16.924 +/- 0.033 |
16.257 +/- 0.024 |
15.887 +/- 0.019 |
16.113 +/- 0.020 |
15.900 +/- 0.022 |
| 12 |
03:21:47.881 |
+16:56:47.21 |
17.007 +/- 0.059 |
16.388 +/- 0.024 |
15.432 +/- 0.012 |
14.900 +/- 0.010 |
15.119 +/- 0.010 |
14.862 +/- 0.011 |
Contact Malcolm Hicken (mhicken @ cfa.harvard.edu)