SUPERNOVA SN2002ap

On January 29.4, 2002, a supernova was discovered on the "outskirts" of the nearby galaxy M74.  At that time it had a "visual magnitude" of 14.5, and was still on the "brightening" phase.  I began observations of it February 2.2.  Here's an image I took of it on that date.

Figure 1.  Color image, constructed from blue, visible (green), red and "clear" filters, on the evening of 2002.02.01.  The supernova, circled, has a visible magnitude of 12.77. The stars that appear as circles are saturated in this 8-bit image, whereas in the original 16-bit images the stars are unsaturated with Gaussian diameters of about 5 "arc. (Color balance is subjective, and is undoubtedly biased in favor of some colors.) [Meade LX-200, 10-inch, f/6.3 Schmidt-Cassegrain telescope, Meade 416XTE CCD with filter wheel; 3-minute exposures for each color; Santa Barbara residence; 2002.02.01/02]

Just to prove that the circled star is "new" here's a picture I took last November (2001.11.27):

Figure 2.  The region where the supernova appeared (2 months later) has an upper limit for any pre-event star of magnitude 18.5.

And another image taken 11 months after the supernova appeared:

Figure 3.  11 months after the supernova outburst it is almost invisible, being only 1/630 as bright as it was near maximum brightness.  In the original, full-resolution image it appears as a 19.3 magnitude star (S/N = 8.8). [Sum of images from 2002.12.20, 2002.12.31 and 2003.01.01; total exposure of 46 minutes; processed with "digital developement" algorithm; Meade LX200 10-inch SCT, SBIG ST-8XE, True Tech CFW, JMI focuser; Sierra Vista, AZ] 

Figure 4.  This is a plot of the supernova's magnitude versus time using red, visible (green) and blue filters.  These data have been corrected for my system's specific filter and CCD spectral response function, using "CCD Transofrmation Equations."  (My system's CTE parameters are:  Tv = -0.015 +/- 0.032, Tvr = 0.987 +/- 0.037, Tbv = 1.89 +/- 0.13).

The supernova was discovered at a Julian Date of 2303.9 (or 2.1 days before the graoh begins).  Note that the supernova is always brighter with the red filter, and that the red excess increases with time.  Peak brightness occurs first with blue, then green, then red, with the red peak occurring 2 days after the blue peak.  The decay phase is smooth, with a slowing of the decay rate (positive inflection of the curves) seen first in blue, then green and finally red. (I had to plot negative magnitudes in order for brightness to increase upward, due to a limitation of my spreadhseet).

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This site opened:  March 13, 2002 Last Update:  January 1, 2003