Bruce L. Gary, Hereford, AZ
Supernova SN2003Z was discovered by "BAO" on the date 2003.01.29.7. It is located in the constellation Ursa Major near the galaxy NGC 2742 which is at coordinates 9:07:32, +60° 29' 17".
Here's a picture from combining exposures taken 2003.01.31.2 and 2003.02.02.22 using red and green filters.
Figure 1. The SN is north (up) of the galaxy nucleus on an outer spiral arm. It averages magnitude 16.7 in this mostly R-filter image. Image field of view is 6.6 'arc EW (northeast is upper-left). [10-inch Meade LX200, f/6.3; SBIG ST-8XE CCD; True Tech Color Filter Wheel; JMI Smart Focuser; combination of ~130 exposures, total exposure 43 minutes for red, 21 minutes for green; Hereford, AZ residence, 4600 feet altitude]
Figure 2. Color picture from RGB images and an unfiltered image taken Feb 7, 2003. Field of view is 9.1 x 6.9 'arc, northeast is at upper-left. Notice that the SN appears slightly blue (consistent with it being brighter in blue than green or red). [Total exposure times are 17 minutes for red, 22 minutes for visible (green), 36 minutes for blue and 8 minutes for unfiltered, all individual exposures were 30-seconds; Meade 10-inch SCT f/6.3, SBIG ST-8XE, Schuler photometry filters in True Tech color filter wheel, JMI Smart Focus; site 4650 feet altitude, Hereford, AZ, USA]
Figure 3. 20030210.25 UT, unfiltered. Faintest stars are mag 18.5. [Focal reducer, yielding f/2.26, no filter wheel, 12x30 sec, image size doubled twice, unsharp mask twice.]
Here are magnitude estimates using photometric V and Rs (Schuler) filters:
Date (UT) R-mag V-mag B-mag
Jan 31.2 16.8 +/- 0.1
17.0 +/- 0.1
Feb 2.2 16.6 +/- 0.1
Feb 3.2 16.5 +/- 0.1
Feb 7.2 17.1 +/- 0.1 17.0 +/- 0.1 16.7 +/- 0.1
From the red magnitudes it appears that a maximum brightness has been reached (at least in red), and the supernovae is now in the decay phase.
The R- and B-magnitudes, Mr and Mb, are calibrated using the USNO-A2.0 star list made from digital scans of the Palomar Observatory Sky Survey (POSS I) E plates. Three nearby stars were used as reference stars. The V-magnitude, Mv, is calibrated using 2 satrs from the GSC (Guide Star Catalog). The USNO-A2.0 or GSC catalogs are not meant for accurate photometry calibration, but they are acceptable for producing approximately correct magnitudes, and are just as valid as well-calibrated reference stars for determining light curve shapes.
Mr and Mv are not corrected for small departures of my system's spectral response from the standard spectral response. The performance of these corrections, using CCD Transformation Equations, is justified when magnitude measurements have sufficient precision to warrant it (about 0.1 mag), when accurate calibration stars are used, and when accuracy is important. In this case, accuracy is less important than the "shape" of the light curve. The shape of this light curve shows that the SN is increasing in brightness still!
This site opened: February 3, 2003. Last Update: February 9, 2003