SIMBAD references

An analytical approach is presented to estimate the mass in the envelope of a condensed white dwarf (WD) and henceforth the mass of the WD itself as both are directly correlated and to estimate the constant mass accretion rate from a simple repeating on-off shape of the X-ray lightcurve for recurrent supersoft X-ray sources. As supersoft X-ray sources have been detected in substantial number by Einstein and ROSAT in the Magellanic Clouds (∼11), the Galaxy (∼7) and M31 (>15) and these objects have been found in part to be of a transient or even recurrent nature it is interesting to relate observational parameters to system parameters in order to explore these unique galactic and extragalactic laboratories. It is shown, that in this approach the critical envelope mass M_env^crit is related to the accretion rate for stable hydrogen burning {dot}(M)_stable, the decay time (or the X-ray on-time) t_decay and the time of recurrence of subsequent outbursts t_recur by M_env^crit={dot}(M)_stable (t_decay-(t_decay)²/t_recur) and that the (constant) mass accretion rate {dot}(M)_accr is given by {dot}(M)_accr={dot}(M)_stable (t_decay/t_recur). Applying this approach to the four transient or recurrent supersoft X-ray sources RX J0513.9-6951, RX J0527.8-6954, RX J0019.8+2156 and RX J0045.4-4154 I deduce constraints for the WD mass and mass accretion rates for these systems (using the relation between envelope mass and WD mass calculated by Fujimoto 1982). This favors high mass WDs (M_WD∼1.3, 1.1-1.3, 1.0-1.3 and 1.35-1.40M_☉) for these systems. Accretion rates of 7.9x10^–8, ≤1.2x10^–7, >8.9x10^–8 and 3x10^–9-4x10^–7M_☉/yr are found. This makes RX J0513.9-6951 and RX J0045.4-4154 strong candidates for the Accretion Induced Collapse, which may happen after an accretion phase of 10⁵-10⁶ and 2x10⁴-2x10⁷ years, respectively. An alternative possibility is that these are systems with considerable mass accretion (of the order a few x10^–1M_☉) which already had occurred over evolutionary timescales. RX J0527.8-6954 and RX J0019.8+2156 are more likely candidates for type Ia supernovae which may happen in a few 10⁶ years. The deduced system parameters have to be modified in case a significant fraction of the envelope of the WD is ejected during the outburst. Especially a lower WD mass is achieved. For GQ Mus (Nova Muscae 1983) consideration of the ejected mass (∼3x10^–5M_☉) leads to a correction of the WD mass from ≤1.0-1.2M_☉ to ≤0.84M_☉. In the supersoft transient and recurrent sources mass ejection (during the outburst as a consequence of the thermonuclear runaway) is not expected to be significant due to the large WD mass and the high accretion rates involved. Such a mass ejection has also not been observed. A constant mass loss due to a wind reducing the effective mass accretion rate may well be present. But such a wind loss will not affect the physical parameters deduced for the condensed WD in supersoft systems. Recurrent supersoft sources may be similar to recurrent novae (in terms of high accretion rates >10^–8M_☉/yr and large WD masses >1M_☉) but may differ due to lack of significant mass ejection during the outburst. This may be due to higher accretion rates close to the value of steady-state nuclear burning of a few x10^–7M_☉/yr.