We report the X-ray observations of two radio pulsars with drifting subpulses : B0834 + 06 and B0826 - 34 using XMM-NewtonṖSR B0834 + 06 was detected with a total of 70 counts from the three EPIC instruments over 50 ks exposure time .
Its spectrum was best described as that of a blackbody ( BB ) with temperature T _ { s } = ( 2.0 ^ { +2.0 } _ { -0.9 } ) \times 10 ^ { 6 } K and bolometric luminosity of L _ { b } = ( 8.6 ^ { +14.2 } _ { -4.4 } ) \times 10 ^ { 28 } erg s ^ { -1 } .
As it is typical in pulsars with BB thermal components in their X-ray spectra , the hot spot surface area is much smaller than that of the canonical polar cap , implying a non-dipolar surface magnetic field much stronger than the dipolar component derived from the pulsar spin-down ( in this case about 50 times smaller and stronger , respectively ) .
The second pulsar PSR B0826 - 34 was not detected over 50 ks exposure time , giving an upper limit for the bolometric luminosity L _ { b } \leq 1.4 \times 10 ^ { 29 } erg s ^ { -1 } .
We use these data as well as the radio emission data concerned with drifting subpulses to test the Partially Screened Gap ( PSG ) model of the inner accelerator in pulsars .
This model predicts a simple and very intuitive relationship between the polar cap thermal X-ray luminosity ( L _ { b } ) and the “ carousel ” period ( P _ { 4 } ) for drifting subpulses detected in the radio band .
The PSG model has been previously successfully confronted with four radio pulsars whose L _ { b } and P _ { 4 } were both measured : PSR B0943 + 10 , PSR B1133 + 16 , PSR B0656 + 14 , and PSR B0628 - 28 .
The XMM-Newton X-ray data of PSR B0834 + 16 reported here are also in agreement with the model prediction , and the upper limit derived from the PSR B0826 - 34 observation does not contradict with such a prediction .
We also include two other pulsars PSR B1929 + 10 and B1055 -52 whose L _ { b } and/or P _ { 4 } data became available just recently .
These pulsars also follow the prediction of the PSG model .
The clear prediction of the PSG model is now supported by all pulsars whose L _ { b } and P _ { 4 } are measured and/or estimated .