V1405 Cas
V1405 Cas was a 5.4 mag transient source first identified in May 2021. Previously associated with the eclipsing white dwarf binary CzeV 3217 Cas (not a CV), this outburst is assumed to be a classical nova, and we thought it represented an interesting opportunity to both test the limits of our observation/analysis techniques and possibly learn something about the system. The period of this system was previously reported as .376938 d, likely the simple orbital period of the white dwarf. It was hoped that we could confirm this period, as well as determine if the magnetic state of the system had changed as a result of the outburst.
The Observations
In the summer of 2021, we used the iTelescope network of telescopes to observe V1405 Cas from two locations; Astrocamp (T18, a 12" Corrected Dall-Kirkham Astrograph) in Spain, and the Mendel Observatory at Merrimack College, which is an 18" Ritchey-Cretien.
We attempted to get as much contiguous observation time as we could over 6 weeks in May and June. An outline of our observations is given in the table below..
The image on the right signifies what a typical Photometry session would look like. The target star (V1405 Cas) is labeled "T1". The comparison stars labeled "C1" through "C6" show us nearby stars that we know a variety about as a way to confirm which star is truly the target star. The numbers that appear after the equals signs describe the magnitudes of each comparison star in the V filter. All Photometry sessions were done using AstroImageJ. Further data analysis was completed using Excel Spreadsheets or Google Sheets, and period analysis was done with VStar.
Light Curve and Period Analysis
The light curves below and in the slideshow do not show how the overall brightness of this source varied with time. This is expected since it was discovered as a new nova, but we actually found there was a second period of brightening in late June (see the figure on the left). As far as I know, we are the only group reporting this behavior - which may or may not be significant, since we are taking all of these images without a filter.
Summary
Identified as a nova without previously known CV-like activity (ATel 14641), we did not know what to expect from this source. As a possible eclipsing binary, observed magnetic activity could have been suppressed either by a low mass transfer rate or large separation. In our observations, although both our individual windows and the combined one show a variety of periods, ranging from 0.25 hr to 0.85 hr, none of them appear to be significant. We must conclude either that this source does not exhibit a clear orbital or spin period, or our observations were not sensitive enough to detect it.
In late June 2021, the period of this source was reassessed by another group using data from TESS. This observatory images the entire sky repeatedly looking for exoplanets, and can be used to determine the periods of these kinds of sources, both in and out of outburst. The result of this study was P=0.1883907 d (4.5 hr), and suggested that this source is a "normal CV" (Schaefer 2021) - but should probably be considered an initial result. Considering that the results above were focused on finding a shorter period, our analysis was re-run (this time with just the longest observation windows), and we find a similar period of 0.183 +/- 0.001 d. The period search (shown below) is not conclusive, but the peak is consistently around 0.18 d and does not strongly depend on the search parameters. The phase plot for this period does not, by eye, show strong evidence for this structure, so we regard our findings as still inconclusive.
