A “combination Nova” Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability
نویسندگان
چکیده
We describe observational evidence for a new kind of interacting-binary-star outburst that involves both an accretion instability and an increase in thermonuclear shell burning on the surface of an accreting white dwarf. We refer to this new type of eruption as a combination nova. In late 2000, the prototypical symbiotic star Z Andromedae brightened by roughly two magnitudes in the optical. We observed the outburst in the radio with the VLA and MERLIN, in the optical both photometrically and spectroscopically, in the far ultraviolet with FUSE, and in the X-rays with both Chandra and XMM . The two-year-long event had three distinct stages. During the first stage, the optical rise closely resembled an earlier, small outburst that was caused by an accretion-disk instability. In the second stage, the hot component ejected an optically thick shell of material. In the third stage, the shell cleared to reveal a white dwarf whose luminosity remained on the order of 10L⊙ for approximately one year. The eruption was thus too energetic to have been powered by accretion alone. We propose that the initial burst of accretion was large enough to trigger enhanced nuclear burning on the surface of the white dwarf and the ejection of an optically thick shell of material. This outburst therefore combined elements of both a dwarf nova and a classical nova. Our results have implications for the long-standing problem of producing shell flashes with short recurrence times on low-mass white dwarfs in symbiotic stars. Subject headings: binaries: symbiotic—novae, cataclysmic variables—stars: dwarf novae—stars: individual (Z Andromedae)—stars: winds, outflows—X-rays: binaries
منابع مشابه
Nuclear Reaction Rate Uncertainties and their effects on Nova Nucleosynthesis Modeling
The nucleosynthesis and other observable consequences of a nova outburst depend sensitively on the details of the thermonuclear runaway which initiates the outburst. One important source of uncertainty in our current models is the nuclear reaction data used as input for the evolutionary calculations. We present preliminary results of the first analyses of the impact on nova nucleosynthesis of a...
متن کاملThe Effect of Composition on Nova Ignitions
The accretion of hydrogen-rich matter onto C/O and O/Ne white dwarfs in binary systems leads to unstable thermonuclear ignition of the accreted envelope, triggering a convective thermonuclear runaway and a subsequent classical, recurrent, or symbiotic nova. Prompted by uncertainties in the composition at the base of the accreted envelope at the onset of convection, as well as the range of abund...
متن کاملA limit for the mass transfer rate in soft X - ray transients
Many black hole X-ray transients are in a low state for several decades until an outburst occurs. We interpret this outburst behaviour as a marginal occurrence of a dwarf nova type disk instability in the cool outer accretion disk. We compute the disk evolution including evaporation of matter from the cool thin disk. This evaporation process causes the transition to a hot coronal flow. The effi...
متن کاملX-ray Observations of Classical and Recurrent Novae in Outburst
I review X-ray observations of classical and recurrent novae in outburst, some of them recently done with Chandra and XMM-Newton for 12 objects. Significant X-ray flux is emitted by the nova shell, with a peak luminosity up to Lx=10 35 erg s in the 0.2-10 keV range. In recurrent nova systems, or in novae hosting a red giant, the source of X-rays may be previous circumstellar matter shocked by t...
متن کاملOn the MV (peak) Versus Orbital Period Relation for Dwarf Nova Outbursts
We present computations for the accretion disk limit cycle model in an attempt to explain the empirical relation for dwarf nova outbursts between the peak visual absolute magnitude and orbital period found by Warner. For longer period systems one sees intrinsically brighter outbursts. This is accounted for in the limit cycle model by the scaling with radius of the critical surface density Σmax ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2005