IM Normae: The Death Spiral of a Cataclysmic Variable?
Myers, Gordon; Monard, Berto; Dvorak, Shawn; Vanmunster, Tonny; Hambsch, Franz-Josef; Knigge, Christian; de Miguel, Enrique; Patterson, Joseph; Kemp, Jonathan; Lemay, Damien; Boardman, James; Menzies, Kenneth; Seargeant, Jim; Ulowetz, Joseph; Warhurst, Paul; Rea, Robert; Roberts, George; Campbell, Tut; Starkey, Donn; Rock, John; Cejudo, David
United States, South Africa, Spain, Belgium, New Zealand, United Kingdom, Canada
Abstract
We present a study of the orbital light curves of the recurrent nova IM Normae since its 2002 outburst. The broad "eclipses" recur with a 2.46 hr period, which increases on a timescale of 1.28(16) × 106 yr. Under the assumption of conservative mass transfer, this suggests a rate near 10-7 M ⊙ yr-1, and this agrees with the estimated accretion rate of the postnova, based on our estimate of luminosity. IM Nor appears to be a close match to the famous recurrent nova T Pyxidis. Both stars appear to have very high accretion rates, sufficient to drive the recurrent-nova events. Both have quiescent light curves, which suggest strong heating of the low-mass secondary, and very wide orbital minima, which suggest obscuration of a large "corona" around the primary. And both have very rapid orbital period increases, as expected from a short-period binary with high mass transfer from the low-mass component. These two stars may represent a final stage of nova-and cataclysmic variable-evolution, in which irradiation-driven winds drive a high rate of mass transfer, thereby evaporating the donor star in a paroxysm of nova outbursts.