On the night of Aug 25/26, 2011, I observed the newly discovered supernova known as PTF 11kly = SN 2011fe in the galaxy M101. This object was discovered just two nights ago, and appears to be a young type Ia event. At a distance of only about 6 or 7 Mpc, this might become bright enough to see visually in small telescopes.
The setup was:
Notes from the night
This is a chart of the field, based on a stack of five R-band images. The field of view is about 10 by 8 arcminutes.
The marked objects appear in a list of comparison stars with magnitudes in BVRI, created by the AAVSO. You can find the original at the AAVSO web site; go to the Variable Star Plotter (VSP) area. I've made a simplified ASCII version of the catalog below, or you can look at the AAVSO's original version in a local copy.
#AUID RA. Dec. Label U B V Rc Ic J H K Comments # Label RA Ra(deg) Dec Dec(deg) ID U B V R I 000-BKD-527 14:03:49.86 [210.95775d] 54:09:05.8 [54.15161d] 117 x - 12.268 (0.057)29 11.735 (0.040)29 11.359 (0.048)29 11.006 (0.054)29 - - - 000-BKD-528 14:04:21.68 [211.09033d] 54:19:22.4 [54.32289d] 119 x - 12.572 (0.068)29 11.948 (0.047)29 11.528 (0.056)29 11.134 (0.063)29 - - - 000-BKD-529 14:02:00.79 [210.50330d] 54:23:15.8 [54.38772d] 128 x - 13.553 (0.062)29 12.751 (0.031)29 12.253 (0.045)29 11.788 (0.056)29 - - - 000-BKD-530 14:01:55.32 [210.48050d] 54:16:21 [54.27250d] 131 x - 13.540 (0.064)29 13.094 (0.044)29 12.716 (0.051)29 12.361 (0.056)29 - - - 000-BKD-531 14:02:02.00 [210.50833d] 54:20:43.9 [54.34553d] 133 x - 14.188 (0.094)29 13.291 (0.057)29 12.772 (0.074)29 12.287 (0.088)29 - - - 000-BKD-532 14:01:49.79 [210.45746d] 54:23:02.7 [54.38408d] 134 x - 14.187 (0.047)29 13.436 (0.033)29 12.970 (0.049)29 12.534 (0.061)29 - - - 000-BKD-533 14:03:13.67 [210.80696d] 54:15:43.4 [54.26205d] 138 A - 14.699 (0.091)29 13.801 (0.046)29 13.230 (0.062)29 12.698 (0.074)29 - - - 000-BKD-534 14:02:54.17 [210.72571d] 54:16:29.5 [54.27486d] 140 B - 14.557 (0.107)29 13.991 (0.074)29 13.581 (0.078)29 13.197 (0.083)29 - - - 000-BKD-535 14:02:29.54 [210.62308d] 54:16:55.2 [54.28200d] 141 C - 14.959 (0.102)29 14.100 (0.045)29 13.598 (0.063)29 13.130 (0.077)29 - - - 000-BKD-536 14:02:31.15 [210.62979d] 54:14:03.9 [54.23442d] 146 G - 15.158 (0.078)29 14.605 (0.029)29 14.204 (0.061)29 13.828 (0.082)29 - - - 000-BKD-540 14:01:50.86 [210.46191d] 54:16:08.1 [54.26892d] 149 x - 15.373 (0.010)29 14.925 (0.000)29 14.635 (0.006)29 14.361 (0.008)29 - - - 000-BKD-538 14:03:23.74 [210.84892d] 54:14:32.6 [54.24239d] 155 H - 16.015 (0.042)29 15.475 (0.000)29 15.133 (0.046)29 14.811 (0.065)29 - - - 000-BKD-539 14:03:05.64 [210.77350d] 54:17:26.2 [54.29061d] 162 x - 16.776 (0.091)29 16.177 (0.000)29 15.640 (0.079)29 15.140 (0.112)29 - - - #Report this sequence as: 5249bgj in the chart field of your observation report. This table is for a 0.25000° fov around PTF11KLY, RA: 14:03:05.81 (210.77421) & Decl.: 54:16:25.40 (54.27372).
I measured the instrumental magnitude of each star with aperture photometry, using a radius of 3 pixels = 4.2 arcseconds in VRI and a radius of 5 pixels = 7 arcsec in B, and sky defined by an annulus around each star. Following the procedures outlined by Kent Honeycutt's article on inhomogeneous ensemble photometry, I used all stars available in each image to define a reference frame, and measured each star against this frame.
Below is a graph of the scatter in differential magnitude versus magnitude in the ensemble solution for the R-band.
The floor of this diagram is about 0.020 mag, which indicates pretty poor data. The floors for each passband were
passband magsig floor -------------------------- B 0.04 V 0.03 R 0.02 I 0.02 --------------------------
I used the output of this ensemble photometry to estimate the uncertainty in the measurement of the SN's magnitude in each passband, using the scatter in measurements of stars at the same apparent brightness as the SN. This uncertainty was smaller than the uncertainty in the catalog magnitude for star "B", which I used to convert the ensemble magnitudes to the standard Johnson-Cousins scale (because star "B" was closest to the SN in color, though still quite a bit less blue). I added the catalog uncertainty for star B and the ensemble uncertainty for the SN in quadrature to estimate the overall uncertainty in the SN's final magnitude.
I did not include color terms in the final magnitudes, because I don't know them well enough. I'll plan to measure them the next clear night in at least a rough manner.
After doing all the work, I end up with these values for the magnitude of SN 2011fe.
Passband JD-2,455,000 Mag +/- -------------------------------------------------- B 799.596 14.05 0.12 V 799.560 13.75 0.08 R 799.554 13.66 0.08 I 799.580 13.63 0.11 --------------------------------------------------
I reported these measurements to the AAVSO via their WebObs tool this morning.
Last modified 8/26/2011 by MWR.