August 28, 2014PTF Summer School Novae in Local Group Galaxies, but really just Andromeda A. W. Shafter San Diego State University Modified and delivered by Lars Bildsten Kavli Institute for Theoretical Physics

Anatomy of a Cataclysmic Variable Secondary star White dwarf Accretion disk Bright spot 

Basic Nova Properties WD cannot burn the material at the rate accreted, and so piles up to ignition, then starts to burn and runs away. Runaway expands the WD radius, either overflowing the Roche Lobe or driving a wind. Luminous! M V ~ -6 to -10 All novae are recurrent at intervals of ~ ~10 5 yr.

Hydrogen Burning is Usually Unstable Fujimoto ‘76; Nomoto et al ‘07; Townsley & Bildsten 2005 Supersoft Sources: Burn H Stably (van den Heuvel et al 1992), or weakly unstable Cataclysmic Variables (CVs): undergo unstable burning, leading to Classical Novae. Most accumulated mass appears to leave. Accumulated mass

Trajectory in HR Diagram

The Role of Extragalactic Nova Studies I. Equidistant sample of novae makes it possible to study relative nova luminosities and fade rates II. Stellar population of novae can be more easily studied Study TNRs in novae from different populations Estimate mean WD masses in novae from different populations III. Possibly useful as distance indicators M V ~  10 for brightest (fastest) novae MMRD relation (brighter novae generally fade faster) Telescope-time intensive

M31: Principal Historical Target Major Studies: Novae Hubble (1929) 85 Arp (1956) 30 Rosino (1964;1973) 142 Ciardullo et al. (1987) 40 Shafter & Irby (2001) 82 Darnley et al. (2006) 20 Others (inc. amateurs) >500 Total: ~1000 Principal Conclusions: Nova Rate ~ 65 +/- 15 yr -1 Appear consistent with a mainly bulge population!

964 Novae Discovered in M

Estimating the RNe population in M31 W. Pietsch et al. have compiled the positions of >900 M31 novae since From these there are a total of ~102 eruptions with reported separations < 5” from 45 potential RN systems. Of these 12 are almost certainly RNe, 4 are possible RNe, with the rest chance positional coincidences.

PTF/iPTF Monitoring of M31

PTF Results on Novae in M31 The MMRD relation was already in question.. Though justified ‘after the fact’, in my view there never was a solid argument for it. Cao et al. 2012

PTF found a novae with a recurrence time of 1 year, ten times more rapid than any in our galaxy. The short recurrence time and the rapid and hot supersoft phase imply a rapidly accreting M>1.3M  white dwarf, one of the most massive yet. It’s fate as accretion continues is unclear!

White Dwarf Masses in Open Clusters

WD Mass Distributions from SDSS Only 5 WD with M>1.3. Very rare, origin often speculated to be WD mergers

MESA is open source: anyone (over 800 users!) can download the source code, compile it, and run it for their own research or education purposes. Bill Paxton, Father of MESA

Second “Instrument Paper” Published in Fourth MESA Summer School at UCSB August 10-14, 2015

Classical Novae from Unstable Thermonuclear Burning of Accumulated Matter Accretion of H/He at low rates leads to a limit cycle of accumulation followed by thermonuclear instability Recurrence times depend on WD mass and accretion rate Stable burning can occur at high rates due to shell thickening Wolf et al. 2013

Accumulated Masses and Stable Burning Wolf et al Higher mass WDs have higher gravity and, hence, smaller accumulated masses. Always an amount of Hydrogen left to burn stably over a prolonged time Seen as a supersoft phase after the novae that is studied in M31 (Heinze et al.) in excellent agreement with theory.

Relation to other Classical Novae Tang et al. 2014

Implications from the Short Recurrence Time MESA Calculations (Wolf et al. ) showed that M>1.3M  and accretion rates of 1-3x10 -7 M  /yr The Super-Soft Phase should be short and hot. Triggered SWIFT follow-up with a rather high cadence...

SWIFT Observations Only 15 day duration. Spectra imply a temperature of nearly 0.1 keV Tang et al. 2014

Theory and Observations place WD mass in the range Tang et al. 2014

Conclusions Goes off again in Nov-Dec 2014 ! Excellent system for testing our theories of classical novae We don’t know whether the WD mass is increasing is decreasing, many would like to say that this is a Type Ia progenitor, but we honestly have no idea... IF it keeps most, then the core will either unstably ignite (if C/O) or undergo catastrophic electron captures (if O/Ne) in one million years.