Paul Boley (P.I.) and the astronomy classes of Grosse Pointe North and South.
Purpose
The purpose of this year's Nova Search project was to analyze new and existing observational data for new novae, expand and reorganize our nova database to adjust for the newly available epochs
from past years, and to replot the light curves and the map. We created new procedures for determining magnitudes that could not be calculated by using the regular macros method in Scion Image,
and used new graphing and fitting routines. We reanalyzed our data to create a nova subclass "AB". Finally, we tested a new hypothesis, stated below.
Hypothesis
In addition to looking for new novae, we wanted to investigate the relationship between the maximum observed magnitude and the class of the nova.
Procedures
This year, there were seven new epochs of data available. The "epoch" column of our data table had to be altered to account for this, as several of the new epochs were in between two older ones. For example, novae which occurred during the 18th epoch of last year's data now occur in the 19th, with the inclusion of a new epoch 18. To make this process easier, we created a data table of all the epochs (Fig 1), showing the new and old numbering, the Julian date and time, the days elapsed from the first epoch, and notes about which epochs were new or renumbered.
Light curves of all the novae which occurred in three or more epochs were plotted using a program called gnuplot (http://www.gnuplot.info/). This program provided several advantages over the program used in previous years, including error bars for each data point and more flexibility in formatting the graphs. The curve fits were analyzed using a program called PSIPlot, which gave us correlation value for the fit.
There were several novae, from this year and past years, for which we initially could not get magnitudes because they were too close to the edge of the field. This year, we used two different methods for getting magnitudes: visual bracketing, and smaller photometry circles. For visual bracketing, the magnitudes of two other stars in the same field and epoch as the nova, one brighter, and one dimmer, were used to narrow down the magnitude of the star. The magnitudes of these stars were calculated using the magnitude macro.
On some novae, smaller aperture radii circles were used. This method was used primarily on novae whose outer edges were within 5-10 pixels of the edge of the field. Because the quality of these magnitude determinations is significantly lower, a "Comments" field has been added to the data table.
Data
A total of 24 new novae were discovered this year. Of those 24, only 3 occurred in previously unavailable epochs. The remaining 21 novae were found in epochs which were previously available. This is attributed to improved software routines and easier usability.
Analysis
After all the novae were graphed and fitted, they were classified as to type NA, NA and NAB. No type NC novae were found. We read about another category, NAB which was described as "nova that change by more than three magnitudes from their peak in more than 100 days but less than 150 days" (Jones, Kenneth Glynn, ed., Webb Society Deep-Sky Observer's Handbook Volume 8, Variable Stars, 1990). So we added this type to our list.
The novae that had light curves were plotted on an image of M31 to look for patterns in their distribution. None was found. Finally, the novae were sorted by groups and their maximum magnitudes were averaged.
There are 2 type NA, 5 type NAB and 13 type NB novae. The magnitude data for these types are as follows:
Type
Maximum Magnitude Recorded
Average Range of Maxima
NA
15.79
15.67-15.99
NAB
16.08
14.97-17.42
NB
16.49
15.50-17.45
Conclusions
There seems to be a relationship between the rate of decline of the nova and its absolute magnitude: the faster the decline, the intrinsically brighter the nova. There does not seem to be a pattern for where these types occur.