On the night of Aug 09/10, 2013, I observed UZ Boo and SN 2013ej in M74. The sky was covered with broken clouds, unfortunately, so I managed only a few measurements, and they aren't very good.
The main setup was:
Notes from the night
I took a long series of images of UZ Boo, but the poor conditions made it difficult to get good measurements from them. Look at the image-to-image zero-point offsets:
Moreover, UZ Boo was very faint tonight, as it had faded considerably since its initial outburst. Take a look at the picture below, which is a composite of 5 30-second images.
I measured both UZ Boo and the star labelled "A", UCAC4 561-055134, which has mag V = 11.094 according to the AAVSO chart 12447AMF. Remember that my images were taken without a filter. If we simply add the difference in instrumental mag to the V-band mag of star "A", we get
JD 2456514.572 V = 16.7 +/- 0.1
SN 2013ej is a Type II supernova in the relatively nearby galaxy M74. It was discovered by the KAIT group some time (a week?) before maximum light. Here's a chart showing the galaxy, the SN, and some reference stars:
The reference stars marked above have magnitudes in AAVSO chart 12459CA, as follows:
letter B sigB V sigV R sigR I sigI B 13.012 0.019 12.510 0.019 12.154 0.019 11.834 0.019 F 13.848 0.026 13.065 0.022 12.622 0.025 12.152 0.027 H 14.338 0.029 13.692 0.024 13.329 0.029 12.964 0.030 I 14.832 0.027 13.912 0.023 13.416 0.026 12.939 0.030 K 15.192 0.034 14.613 0.027 14.275 0.034 13.915 0.036
After discarding the bad images, I was left with 17, 4, 5 and 6 images in B, V, R, and I, repsectively.
Using aperture photometry with a radius of 4 pixels (radius of 7.4 arcsec), I measured the instrumental magnitudes of a number of reference stars and the target. 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. I used the AAVSO magnitudes, plus color terms to convert the ensemble instrumental magnitudes to the standard Johnson-Cousins BVRI scale.
Results from this morning are:
filter mag mag_uncert Julian Date B = 12.964 +/- 0.056 (ens 0.018 zp 0.053) 2456514.70262 V = 12.527 +/- 0.075 (ens 0.022 zp 0.072) 2456514.69471 R = 12.297 +/- 0.051 (ens 0.022 zp 0.046) 2456514.68018 I = 12.239 +/- 0.034 (ens 0.018 zp 0.029) 2456514.68665
The uncertainties here are dominated by transforming the instrumental magnitudes to the standard scale.
Grab the text file below for all the RIT measurements of SN 2013ej. All these values have been recomputed with the new color terms of UT 2013 Aug 05.
Last modified 08/12/2013 by MWR.