A Spectroscopic and Photometric Survey of Classical Novae in M31 Conor Ransome (Astrophysics Research Insitute, LJMU) Co-authors: Matt Darnley, Phil James, Stacey Habergham-Mawson and Mike Healy Email: C.Ransome@2018.ljmu.ac.uk Classical novae (CNe) are a subclass of cataclysmic variable comprised of a white dwarf (WD) and a late-type (main sequence to giant, Bode & Evans, 2008) donor which results in a non- terminal explosion once the enough matter has accreted onto the WD such that the pressure at the surface of the WD is adequate to initiate a thermonuclear runaway reaction. Recurrent novae (RNe) are CNe systems where multiple eruptions have been observed, these are systems with a higher mass WD approaching the Chandrasekhar mass and require less accreted mass in order to trigger a TNR due to the higher surface gravity of the WD. RNe are a potential single-degenerate channel to Type Ia supernovae. CNe can be split into two spectral classes, Fe II and He/N based on the strength of emission lines (Williams, 1992) and also the ejecta velocities estimated by the width of the H-alpha profiles with Fe II novae having slower ejecta (up to 2500km/s) than He/N novae (up to 10,000km/s). There are two main hybrid spectral classes: ●Fe IIb exhibit the characterisitic Fe II class lines but the width of the H-alpha profile exceeds that of regular Fe II class novae and more similar to the ejecta velocities of the He/N class. ●He/Nn exhibit the characteristic He/N class lines but with ejecta velocities more similar to the Fe II class. 1. Classical Novae 2. Motivation Previous studies of CNe in M31 have had small samples; for example: 85 – Hubble (1929); 44 Shafter et al. (2011). We have a sample of 180. The environments in which CNe occur can tell us about the stellar populations the systems belong to. In this case we look at UV emission: ●High UV emission points to hot, young O/B stars which reside in young populations with active star formation. Younger populations in the disc are thought to have higher mean WD masses than the bulge which may indicate more He/N novae (Shafter 2013). Galaxies with a central bulge (e.g. M31) have around 80% FeII novae whilst bulgeless galaxies (e.g. LMC) have an equal split of FeII to He/N. Previous work found no difference in the radial distribution of novae of the two spectral classes (Shafter et al. 2011). 3. Methods The sample (compiled using Pietsch et al., 2007) are split into spectral classes and analysed in terms of their spatial distribution and association with UV emission regions. Archival Liverpool Telescope data will be analsyed to make spectral classifications of our CNe. We employ a pixel statistics technique, normalised cumulative rank (NCR) which is usually used in the study of supernova environments (see James & Anderson, 2006) to calculate the relative UV flux of the pixels that a nova falls on in images from the GALEX space telescope. We then use Anderson-Darling (AD) tests to determine if there is a significant difference between the two distributions. We compare the NCR data of the spectral types against each other. Three approaches to looking at the radial distribution of the novae from the centre of M31: ●The offset as seen on the sky. ●The deprojected offsets. ●The isophotal radius. 4. Results The LT had 76 spectra in the archive, 60 were usable to make classifications, we find 48 Fe II novae, 6 He/N novae, 5 Fe IIb hybrids and a single He/Nn hybrid. Despite our much larger sample none of the results of our AD tests were statistically significant. Therefore there is no evidence to suggest there is a difference in either the environments as seen in the NCR analysis or the radial distribution of He/N or Fe II novae in M31. We will produce light-curves to include speed classes (as described by Payne-Gaposchkin, 1964) into our analysis. This investigation will be extended to M33 and the LMC. Above: Novae split into all classes plotted over a Palomar 48-inch Schmidt telescope image of M