The Death Spiral of T Pyxidis (1303.0736v1)

Abstract: We report a long campaign to track the 1.8 hr photometric wave in the recurrent nova T Pyxidis, using the global telescope network of the Center for Backyard Astrophysics. During 1996-2011, that wave was highly stable in amplitude and waveform, resembling the orbital wave commonly seen in supersoft binaries. The period, however, was found to increase on a timescale P/P-dot=3x10^5 yr. This suggests a mass transfer rate of ~10^-7 M_sol/yr in quiescence. The orbital signal became vanishingly weak (<0.003 mag) near maximum light of the 2011 eruption. After it returned to visibility near V=11, the orbital period had increased by 0.0054(6) %. This is a measure of the mass ejected in the nova outburst. For a plausible choice of binary parameters, that mass is at least 3x10^-5 M_sol, and probably more. This represents >300 yr of accretion at the pre-outburst rate, but the time between outbursts was only 45 yr. Thus the erupting white dwarf seems to have ejected at least 6x more mass than it accreted. If this eruption is typical, the white dwarf must be eroding, rather than growing, in mass -- dashing the star's hopes of ever becoming famous via a supernova explosion. Instead, it seems likely that the binary dynamics are basically a suicide pact between the eroding white dwarf and the low-mass secondary, excited and rapidly whittled down, probably by the white dwarf's EUV radiation.

• The paper reveals that T Pyxidis exhibits a stable 1.8-hour photometric wave with a steadily increasing orbital period over 15 years.
• It finds that during the 2011 eruption, the white dwarf expelled mass at a rate greatly exceeding its accretion, indicating erosion rather than growth.
• The results challenge the idea of T Pyxidis as a viable Type Ia supernova progenitor and call for refined models of mass transfer in recurrent novae.

Analysis of "The Death Spiral of T Pyxidis"

The paper "The Death Spiral of T Pyxidis" offers a rigorous investigation into the photometric and orbital characteristics of the recurrent nova T Pyxidis. With data spanning 1996 to 2011, researchers tracked the 1.8-hour photometric wave, indicative of the orbital wave in supersoft binaries. Notably, the period was observed to increase at a timescale of $3 \times 10^5$ years, suggesting a mass transfer rate of $\sim 10^{-7} M_\odot$ per year during quiescence.

Findings and Observations

1. Photometric Observations: During 1996-2011, the photometric wave was stable in amplitude and waveform. However, after the 2011 eruption, the orbital period increased by 0.0054(6)%, offering a measure of the mass ejected during this event.
2. Mass Ejection vs. Accretion: The paper indicates that during the 2011 eruption, T Pyxidis ejected a significant mass, corresponding to over 300 years of accretion at the pre-outburst rate. Despite a 45-year interval between eruptions, the erupted white dwarf expelled at least six times more mass than it accreted. This finding implies that the white dwarf is eroding rather than accumulating mass.
3. Orbital Period Dynamics: A persistent photometric wave with a stable 0.07622-day period was confirmed. Over the observed years, a steady increase in the orbital period was noted, consistent with mass-loss dynamics.

Implications and Theoretical Considerations

The primary implication of this paper is the likelihood that the white dwarf in T Pyxidis will not culminate in a Type Ia supernova, as its mass appears to be decreasing over time. This contradicts earlier assumptions that such recurrent novae, by virtue of their high mass accretion rates, are potential candidates for these supernovae events.

From a theoretical standpoint, the findings challenge the conventional understanding of mass dynamics in recurrent novae. With T Pyxidis illustrating a suicide pact dynamic between the eroding white dwarf and the low-mass secondary, it posits the question of whether other recurrent novae might exhibit similar mass-loss characteristics.

Future Directions

Ongoing tracking of the orbital period in T Pyxidis, coupled with more detailed observations during future eruptions, can provide further insights into the long-term evolution of this and similar systems. The elucidation of mechanisms contributing to angular momentum loss would also deepen understanding of mass ejection processes in novae.

Research should also investigate whether other short-period cataclysmic variables exhibit similar mass-loss behavior, potentially affecting population statistics such as the local census of variable stars. Increased precision in determining binary parameters in such systems will refine models of mass transfer and evolutionary pathways.

This paper on T Pyxidis offers a substantive contribution to astrophysical knowledge, particularly in the dynamics of white dwarf and secondary star interactions in recurrent nova systems. The findings necessitate a re-evaluation of the potential for mass growth in white dwarfs within similar binary structures, impacting theoretical models of stellar evolution and supernova progenitors.