Chris Duffy
Gather.town id
TA05
Poster Title
New Evidence of the Diversity In Outbursting AM CVn Systems
Institution
Armagh Observatory and Planetarium
Abstract (short summary)
Cataclysmic Variables (CVs) are excellent sources to study accretion physics. Many CVs exhibit outbursts as a result of disc instabilities. CVs are binary systems with periods ranging from ~0.5 days to a few minutes. At the extreme short end of this period distribution are the hydrogen deficient AM CVn systems. We present results of our analysis of 15 years of photometric data of 8 AM CVn systems with periods between 22.8 and 26.8 minutes found in the period instability region. Our data is drawn from GOTO, ZTF, Pan-STARRS, ASAS-SN and Catalina all-sky surveys, as well as amateur observations collated by the AAVSO. This long term data has given us the opportunity to characterise the full range of behaviour in these systems and demonstrates that they show the same diversity as the hydrogen accreting CVs. Our results show that AM CVn systems in the period instability region are not a homogeneous group and implies the nature of the mass donating star is a key factor in their outburst properties. We find systems showing long super outbursts and standstills, others showing shorter more regular super outbursts and others only in a high state — something unpredicted by the existing theory. We also used TESS full frame images of KL Dra, from this we detected normal outbursts appearing as an immediate precursor to it super outbursts, a feature which has never been observed before in AM CVn systems. Our results highlight the breadth of the behaviour seen in hydrogen deficient systems and will inform the theoretical modelling of them.
Plain text (extended) Summary
We present results of out analysis of up to 15 years of photometric data from eight AM CVn systems with periods in the disc instability region. We find that systems in the previously identified disk instability region are not a homogenous group. Various members of the analysed sample show long super outbursts and standstills, others show shorter regular super outbursts, and a final group only appears in a high state with no apparent instability. Using TESS full frame images we find the first evidence of normal outbursts appearing as a precursor event to a super outburst in an AM CVn system.
These findings demonstrate that the behaviour of outbursting AM CVn systems is more subtle and complex than previously believed with more than just orbital period acting to govern the behaviour seen. These results will inform future modelling work in regards to outbursting AM CVns.
Figure 1 shows an artists impression of an AM CVn system showing an accretion stream
Figure 2 show the prototype of GOTO with the dome open around sunset
Figure 3 shows samples for the lightcurves of each of the sources considered with times selected to best highlight the different behaviours. Data points are coloured differently to acknowledge the different data sources.
Figure 4 shows the lightcurves of 5 super outbursts in KL Dra detected by Tess. Each shows an initial rise in brightness followed by a dip approximately 1 day after onset followed by another rise soon after to maximal brightness.
These findings demonstrate that the behaviour of outbursting AM CVn systems is more subtle and complex than previously believed with more than just orbital period acting to govern the behaviour seen. These results will inform future modelling work in regards to outbursting AM CVns.
Figure 1 shows an artists impression of an AM CVn system showing an accretion stream
Figure 2 show the prototype of GOTO with the dome open around sunset
Figure 3 shows samples for the lightcurves of each of the sources considered with times selected to best highlight the different behaviours. Data points are coloured differently to acknowledge the different data sources.
Figure 4 shows the lightcurves of 5 super outbursts in KL Dra detected by Tess. Each shows an initial rise in brightness followed by a dip approximately 1 day after onset followed by another rise soon after to maximal brightness.
URL
christopher.duffy@armagh.ac.uk
Poster file