http://arxiv.org/abs/1401.2426
The iPTF detection of the most recent outburst of the recurrent nova system RX J0045.4+4154 in the Andromeda Galaxy has enabled the unprecedented study of a massive (M>1.3 $M_\odot$) accreting white dwarf (WD). We detected this nova as part of the near daily iPTF monitoring of M31 to a depth of R$\approx$21 and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of M_R$\approx$-6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast novae. It shows optical emission lines of He/N and expansion velocities of 1900 to 2600 km/s 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with $kT_{eff}$ $\approx$ 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is a recurrent nova with a time between outbursts of approximately 1 year, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993, and the source was well characterized as a M>1.3 $M_\odot$ WD SSS. Both the duration and effective temperature of the SS phase imply M>1.32 $M_\odot$, while MESA models of accreting WDs allow us to constrain the accretion rate to $\dot{M}>1.7\times10^{-7}$ $M_\odot$/yr and WD mass >1.32 $M_\odot$. If the WD keeps 30% of the accreted material, it will take less than a Myr to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution.
Mon, 13 Jan 14
24/39
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