SIMBAD references

The empirical relation between the X-ray luminosity (in the 2-10keV band) and the rate of spin-down energy loss L_sd of a sample of 39 pulsars is re-examined considering recent data from ASCA, RXTE, BeppoSAX, Chandra, and XMM-Newton and including statistical and systematic errors. The data show a significant scatter around an average correlation between L_x,(2–10) and L_sd. By fitting a dependence of L_x,(2–10) on the period P and period derivative {dot}(P) of the type L_x,(2–10)∝P^a[{dot}(P)]^b, we obtain a=-4.00 and b=+1.34 (i.e. a≃-3b). This translates into the relation L_x,(2–10)=L_x,nor(L_sd/erg.s^–1)^1.34 with a normalization L_x,nor=10^–15.3erg/s . However, the reduced χ² is large (=7.2) making the fit unacceptable on statistical ground. All the X-ray luminosities lie below a critical line L_x,crit: the corresponding efficiency of conversion of rotational energy into 2-10keV X-rays is η_