CONSTRAINING JET THEORIES USING NOVA TBURSTS

摘要

It is commonly accepted that jets have not been observed in cataclysmic variables (CVs) so far. This absence was recently explained by their low mass transfer rates compared with objects with jets. A mass accretion limit for jets in CVs was proposed to be M ～ 10~(-7) to 10~(-6) solar mass yr~(-1). There was, however, a report of evidence of jets in V1494 Aql, the second nova that erupted in Aquila in 1999. In this work, we estimate the mass transfer rate of this system around the reported event and show that it is consistent with the above theoretical limit for jets. We further propose that the X-ray flare that was observed in this object may be connected with a jet as well. The appearance of jets in novae is actually expected, since during the early decline from outburst some are like supersoft X-ray sources, in which jets have been found. The detection of jets in novae also fits the suggestion that in addition to the presence of an accretion disk, a hot central source is required for the formation of jets. The observations of jets during the transition phase in V1494 Aql can be regarded as evidence of the early existence of the accretion disk in the system. This conclusion supports our previous suggestion for a link between the transition phase in novae and the reestablishment of the accretion disk. We further speculate that jets may be restricted to transient novae. If our ideas are confirmed, jets should be common in transient novae and may be formed several times during the transition phase and perhaps even long after it ends. In classical novae jets may be launched and observed in real time. As binary systems, these objects are easy to study. Novae may, therefore, be key systems in understanding the formation and evolution of jets and ideal targets to test and constrain jet theories. Adding novae to the classes of systems showing jets should be very exciting and rewarding.